2016 NGWA Groundwater Summit: Alphabetical Content Listing

Anything Else Groundwater

Application of Argon-39 Age Dating to Enhance Groundwater Age Distribution Estimation

Signe White
Argon-39 is created in the atmosphere by cosmic rays and has a half-life of 269 years. As an inert noble gas with constant atmospheric concentration, it is an ideal tracer for dating groundwaters with no terrigenic production and with intermediate ages in the range of 50-1000 years, filling the current gap existing between the commonly used tracers 3H/3He or 85Kr (< 50 years) and 14C (>1000 years). Pacific Northwest National Laboratory has developed a process for purifying and detecting 39Ar in groundwater using ultra-low-background proportional counters (ULBPCs) in their shallow underground laboratory. Samples for the 39Ar measurements are collected by extracting the dissolved gases from 3000-5000 L of groundwater using a membrane degasification system, and then purified to remove gases other than argon.  The 39Ar is then detected through direct beta counting using ULBPCs loaded with a mixture of sample Ar and geologic methane. The resulting measurements yield the 39Ar specific activity of a sample as a percentage of that in modern argon. This percentage, along with upper and lower bounds corresponding to a selected statistical confidence level, then yields a sample age range. We demonstrate the value of such data in estimating the age distribution of groundwater, using recent theoretical advances that relate the measurement of a radio-decaying tracer concentration to the Laplace transform of the age distribution. Results demonstrate the value of 39Ar data in characterization of the age distribution in cases ranging from very young to carbon-14-old groundwaters.

Application of 129I/127I Ratios in Groundwater Studies Conducted at Los Alamos National Laboratory, New Mexico

Patrick Longmire, PhD
Los Alamos National Laboratory (LANL) is an operating nuclear site that has released treated effluents from three plutonium-processing facilities since the mid 1940s. The radioisotope 129I (T1/2 = 15.7 Myrs) derived from235U and 239Pu processing at LANL is locally detected in groundwater above background concentrations. This isotope provides a unique tracer for groundwater investigations conducted at LANL that helps to identify source releases linked to groundwater-flow paths in aquifers subject to binary and ternary mixing of natural- and industrial-derived waters containing chromate and other chemicals. Bromide, chlorate, chloride, nitrate, perchlorate, sulfate, and tritium were associated with multiple outfalls at LANL and, therefore, do not provide unique chemical signatures identifying a specific point of release or source. Natural and anthropogenic ratios of 129I/127I measured in groundwater samples collected at LANL were quantified using accelerator mass spectrometry at Purdue Rare Isotope Measurement Laboratory, Purdue University. Anthropogenic ratios of 129I/127I range from 1,252 X 10-15 to 17,367 X 10-15 within perched-intermediate groundwater present in volcanoclastic and basalt aquifers (210 – 216 m depth). Anthropogenic ratios of 129I/127I range from 359 X 10-15 to 4,350 X 10-15 within the regional aquifer (280 m depth) consisting of volcanoclastic sediments of variable hydraulic properties. Local background ratios of 129I/127I have a narrow range of 171 X 10-15 to 378 X 10-15 in the regional aquifer. Dissolved iodide measured in groundwater at LANL is stable dominantly as iodate. Background concentrations of dissolved iodate (0.1 to 33.2 nM) are less variable compared to anthropogenic iodate (8.0 to 246 nM) in groundwater at the site. Variability in concentrations of anthropogenic iodate is controlled by heterogeneous source releases of iodate over time and non-uniform mixing of groundwater in the different aquifers.

Investigating the Upper Pierre Aquifer through Regional and Site-Specific Data and Data Integration into a GIS

Theresa Jehn-Dellaport, P.G.
The Upper Pierre aquifer, an under-studied, mostly undeveloped groundwater aquifer, may provide a much needed resource for ranchers and the oil and gas industry within Northeastern Colorado.  Known to expand at least throughout the Cheyenne Basin, the Upper Pierre aquifer lies within the upper unit of the Upper Cretaceous Pierre Shale, underlying the Laramie-Fox Hills aquifer, where present.  Regional data suggest the aquifer to have a thickness of 800-1000 feet  and recent drilling of production wells into the Upper Pierre aquifer, although limited, have been yielding up to 300 gpm. 

Oil and gas exploration drill-hole geophysical logs have been the primary regional source of data for interpretation of the geometry of the Upper Pierre aquifer.   The geophysical logs display a conspicuous spontaneous potential (SP) and resistivity signature within the aquifer, with a distinct low-amplitude deflection in both the SP and resistivity mid-way through the thickness of the aquifer, indicative of the Pierre Ash.   Site-collected data, such as lithologic logs, sidewall cores, and drill cuttings suggest the aquifer to be composed of grey siltstone/sandstone with a calculated specific yield value of 0.17.

A database of over 400 interpreted oil and gas geophysical logs was integrated into a Geographic Information System (GIS).  The data were processed to geostatistically create continuous surfaces representative of the upper and lower elevations of the aquifer.  Spatial characteristics of the aquifer, such as its relation to other aquifers and areas of subcrop and outcrop, have also been defined using GIS capabilities.  Hydrogeologic cross-sections and three-dimensional renderings are being used as key decision-making tools for interested parties in adjudicating the groundwater of the Upper Pierre aquifer.

Laser Sensing for Monitoring Headspace Methane

Daniel Soeder, National Energy Technology Laboratory
The migration of methane gas in groundwater is a concern for many domestic well users, especially in areas of natural gas development.  Commercial gas sensors for monitoring methane in groundwater wells typically utilize electrochemical devices.  Laser sensing has proven to be a more reliable and accurate technology for detecting methane and other gases in air.  A tuned laser produces light at wavelengths equal to the spectral absorption bands of the gas in question.  The presence of the gas in the path of the laser beam attenuates the light as a function of concentration, which is then measured with a photocell.  Laser gas detectors are solid state devices that only require the introduction of the gas sample into the laser beam path.  Laboratory tests with a commercial unit had an accurate detection range from 10 ppm methane to the lower explosive limit of 5%.

Although these sensors perform well in a laboratory environment, deploying them in the field for environmental monitoring is challenging.  Along with power supply and data storage issues, the major problem is moisture condensation in the sensor, which can create data inconsistencies.  Field deployment of the laser sensor for continuous monitoring of methane in the headspace of a groundwater well required the use of a commercial gas drying method to remove humidity.  Low power requirements were critical.  As configured, the field-deployable device collects an air sample from the well headspace, pumps it through a drying system, and then into the laser sensor to measure methane concentration.  Ambient temperature and pressure are also measured before discharging the gas.  The entire unit is contained within a medium-size utility box, and field sampling requires only the insertion of a 5 mm (1/4 inch) collection tube into the monitoring well headspace.  Field tests are ongoing in support of a patent application.

Using a Hydraulic Profiling Tool in Site Characterization Activities

Todd K. Knause
Rapid, accurate subsurface characterization is critical to site investigations. The Hydraulic Profiling Tool (HPT) is a direct push logging tool that continuously measures the pressure required to inject a constant flow of water into the soil as the probe is advanced into the subsurface. The HPT allows for the creation of fast, continuous, real-time profiles of soil hydraulic properties in both fine- and coarse-grained material. The probe provides data about the formation lithology, permeability, and the piezometric profile, which allows for the development of detailed lithologic cross sections of the subsurface conditions and the detection of high electrical conductivity fluids (brines) in soil. 

The HPT was advanced down into a heterogenous alluvial deposit to a depth of 100 feet or refusal.  The hydrogeologic data collected was used to evaluate where to collect discrete soil and groundwater samples, and set monitoring well screens during the subsequent Sonic drilling activities. The pressure, flow, and electrical conductivity (EC) data is recorded on a series of logs providing real time high resolution site characterization data.  The injection pressure logs were used to infer hydrostratigraphy, including transmissive zones that may represent potential preferential migration pathways for groundwater contaminants and low permeable zones that may act as confining layers.  The EC measurements were used to evaluate lithology and potential Total Dissolved Solids (TDS) impacts to groundwater. Discrete groundwater samples were collected from highly transmissive zones, field tested for specific conductance, and submitted to a laboratory for TDS analysis to establish an appropriate ratio of conductivity to TDS.  Lithologic interpretations were confirmed by continuous soil cores collected with a Sonic drill rig during monitoring well installations.  Disturbed and undisturbed soil samples were collected and analyzed for chemical and physical properties.

Anything Else Groundwater

Analyzing the Reservoir Beneath Our Feet: Denver Water's Aquifer Storage and Recovery Pilot Project

Bob Peters, PE
Denver Water’s long-term planning indicates the need to develop additional water supplies.  Uncertainties such as climate change and population growth could present scenarios with serious challenges to meeting future water needs for our customers.  To address these scenarios Denver Water is investigating new types of potential supplies, including aquifer storage and recovery, or ASR.  Denver Water is conducting a pilot project to evaluate whether ASR using the Denver Basin aquifers is a technically and economically feasible method to increase water supplies.  Denver Water could benefit from ASR if it were able to store water in the aquifers during wet years and recover the water to help meet demands in dry years.  To access the aquifers, wells would be drilled into the Denver Basin throughout Denver and connected to the potable water distribution system.  Along the Front Range region of Colorado, several utilities have employed, with varying degrees of success, ASR within the Denver Basin.  Within the City and County of Denver, there are relatively few Denver Basin wells; so data on the formations and their productivity is limited. In 2015, Denver Water drilled four exploratory boreholes within Denver to help fill hydrogeologic data gaps. Standard geophysical logging was conducted in the boreholes as well as nuclear magnetic resonance (NMR) logging.  Used for many years in the oil exploration industry, NMR logging technology has only recently been adapted for use in groundwater resources investigations.  An analysis of potential aquifer productivity was performed using the logging data gathered from the four boreholes along with data from operating Denver Basin wells.  Findings of the analysis will be used to help identify a site for an ASR pilot well facility, which will be operated to further evaluate the viability of ASR for Denver Water.

Building a Case for EPA Compliance Utilizing Remote Monitoring in CAFO Lagoons

Jeff Dance
In concentrated animal feeding operations (CAFO’s) lagoons emit substances, by air or overflow. Airborne emissions include ammonia, hydrogen sulfide, methane, carbon dioxide and ammonium nitrates. Equally as harmful are lagoon overflows which can release bacteria, pesticides and antibiotics. The EPA has shown nitrate concentrations, in drinking water cause developmental deficiencies and can fatally deprive the bloodstream of oxygen.
Remotely monitoring, logging and transmitting information, using report by exception technology is critical to proactively managing animal waste and its impact on ground water.
Integrating data logging monitors with industrial data gateways is practical, efficient and cost effective. A variety of telemetry options links hardware in the field to a secure, cloud-based interface. The result is big data that can be analyzed, viewed and configured and acted upon in real time anywhere.

Optimizing Success of Waterwell Rehabilitations

Fred Rothauge
By using both proven and innovative technology and having a better understanding of a water wells behavior it is possible to increase the success of well rehabilitation efforts.  Several parameters should be tested and evaluated prior to implementing the rehabilitation plan. These parameters will be explored.   The presentation will pinpoint the root cause for failure and provide best practices to eliminate failure.   With over 30 years of experience, and hundreds of well rehabs completed, the unexpected will be valuable knowledge worthy of sharing. Well professionals, geologist, government officials, and public health professionals will be interested in what was learned.

Urban Green Stormwater Infrastructure: How Much Is Infiltrating?

Mark Maimone, PhD, PE, D WRE, BCEE
There is an emerging trend in urban stormwater management as more and more major U.S. cities are considering green stormwater infrastructure (GSI) to reduce stormwater impacts to their separate and combined sewers. Philadelphia is implementing the most ambitious GSI program in the U.S. to meet its combined sewer overflow control obligations. A key feature of GSI is the capture and infiltration of stormwater before it reaches the sewer system. Because of the scale of the Philadelphia program, Philadelphia Water has implemented a sophisticated monitoring program to answer a number of basic questions about the functioning of urban GSI. The program includes monitoring of individual GSI practices to develop storm by storm water balances, and to calculate inflow, infiltration/evapotranspiration and slow release back to the sewer. It also includes hundreds of infiltration tests and an examination of the infiltration test results compared to actual infiltration rates for completed projects.

Groundwater monitoring wells have been installed adjacent to GSI to answer the basic question of the impacts of urban infiltration on the water table and potential flooding of nearby basements, particularly in right-of-way systems (rain gardens, infiltration tree trenches, etc.). Monitoring well data are coupled with continuous monitoring data collected within the GSI to evaluate the magnitude and timing of water table increases due to different storm events and the recovery period when the water table recedes to baseline depths (pre-storm conditions). Monitoring wells are also being routinely monitored at a regional scale to evaluate how the regional water table is responding to large scale implementation of GSI.

Philadelphia Water is using monitoring data to develop design guidelines, assess infiltration impacts, and to show regulatory agencies how GSI can be an effective means of reducing combined sewer overflows.

Anything Else Groundwater

Accuracy Testing of New and in-Use Electric Groundwater-Level Measurement Tapes

Rodney Sheets
The U.S. Geological Survey (USGS) measures the water level in more than 15,000 wells each year and, increasingly, these measurements are done with electric tapes.  Approximately 650 electric water-level tapes are in use by the USGS and USGS standards require regular calibration of these and all instruments used for hydrologic measurement. 

Electric water-level measurement tapes are generally assumed to be accurate to ±0.01 foot (ft), but little information is available from the manufacturers and USGS field office calibration and initial calibration studies by the USGS Hydrologic Instrumentation Facility (HIF) indicate that this accuracy is seldom attained. This study was designed initially to determine the accuracy of six models of new, unused electric groundwater tapes often used by the USGS for routine water-level measurements and groundwater studies. A tape-calibration system was designed and built at the HIF. The tape-calibration system compares the length of each electric tape to a calibrated-steel reference tape and measures each probe’s activation accuracy. The tape-length accuracy combined with the probe-activation accuracy gave the overall measurement accuracy of the tape.  Results demonstrated that none of the electric-tape models tested consistently met the suggested accuracy of ±0.01 ft, and that most tapes were accurate to approximately ±0.05 ft per 100 ft without additional calibration.  Precise calibration of in-use tapes is necessary to gain the required accuracy.  Comparisons between results at established metrology laboratories and the tape-calibration system at the HIF indicate that the HIF system is adequate for calibration of USGS electric tapes, and a program has been established to retrieve all USGS field electric water-level tapes for evaluation and calibration. Results of this ongoing evaluation and calibration of in-use USGS electric tapes will be presented.

Adding Analytical Power By Applying Underused and Unappreciated Techniques

Graeme Bowles, P.G.

Groundwater analysts can add significant analytical power to their portfolio of evaluation techniques, by employing underused and underappreciated techniques from other technical disciplines. Examples of these techniques will be presented, from groundwater projects that have included collection of time-varying data. This reflects the proliferation of in-situ data recorders deployed in observation wells, for measuring water levels and other parameters. In addition, time-varying data from SCADA systems and similar operational platforms continues to play an important role on many groundwater projects, especially those involving the management of water supply well fields and hazardous waste remediation pumping and injection wells. The underused and underappreciated techniques address a range of analysis objectives, and generally provide supplementary results, complementing mainline methods used by groundwater professionals.

Graphing of single and double mass curves – a technique used widely in surface water hydrology and meteorology – helps analysts discern trends that may be very difficult to perceive, as well as facilitating identification of changes in trends and comparisons between conditions at different monitoring points. Examples will demonstrate the use of single and double mass curves for characterization of remediation system pipe clogging, and for assuring maintenance of wetland hydroperiod.

Signal-processing techniques have been developed extensively within technical disciplines such as electrical engineering. One of these techniques, called Fast Fourier Transform (FFT), provides frequencies of multiple signals within time-series of data. Examples of groundwater-related FFT applications include identification of coastal/earth tide impacts on water levels versus signals from diurnal, every-other-day, and weekly irrigation pumping wells. Such efforts can be extended to help identify specific pumping wells potentially affecting plume capture and aquifer restoration efforts.

Enhancements of these techniques, for increasing usefulness on groundwater-related projects, will be highlighted. In addition, other similar techniques will be cited, and recommendations provided for wider application of underused methods by groundwater professionals.

Reductive Degradation of PFOS in Groundwater Using Nano-Scale Zero Valent Iron

Xin Song, Professor
Perflurooctane sulfonate (PFOS), one of the most often detected perfluorinated chemicals, has been defined as an emerging contaminant due to its ubiquitous distribution, high persistence and strong bioaccumulation. Research on the oxidative decomposition of PFOS using persulfate shows that it is quite resistant to oxidation process compared with perfluorooctanoate (PFOA). Here we studied the reductive degradation of PFOS utilizing nano-scale zero valent iron (nZVI). The fluorination ratio and decrease of PFOS were used to evaluate the degradation efficiency of PFOS.

The effect of different environmental conditions, including nZVI dosage, temperature, pH and dissolved oxygen concentration in water, were investigated. It was found that the defluorination ratio increased significantly with the increase of nZVI dosage. At the dosage of 11.2g/L, the PFOS defluorination ratio reached nearly 100%, demonstrating a complete PFOS decomposition. The defluorination ratio increased from 60% to nearly 100% with the temperature increasing from 27 °C to 40 °C. However, the defluorination ratio decreased significantly if the solution pH was adjusted from 7.5 to 3 using hydrochloric acid. Comparative experiments showed that dissolved oxygen in water would affect the reductive defluorination of PFOS. In addition, kinetic experiments were conducted to investigate the reaction rate. To investigate the PFOS degradation mechanisms, further work to identify the degradation products are being carried out.

The Quest for Relevant Baseline Groundwater Data in the Context of South Africa's Potential Energy Futures

Audrey Levine, Ph.D., P.E., BCEE
In many parts of the world, stressors on energy reliability and security are triggering intense interest in development of new energy resources, such as extraction of gas and oil from unconventional sources (e.g. shale, coalbeds, tight sands). However, many uncertainties surround the interdependencies between energy development and water resource protection. The quality and availability of groundwater resources can be vulnerable to impacts from energy development, particularly in conjunction with water scarcity concerns. While monitoring and modeling of groundwater systems can provide insight into potential contamination pathways and mitigation measures, it can be difficult to obtain statistically sound baseline data in cases where energy development activities pre-date monitoring programs. In addition, there is a lack of consensus on exactly what comprises baseline data in terms of monitoring parameters, frequency, and data analytics. 

In South Africa, there is increasing interest in improving energy reliability and security through developing unconventional energy sources. However, the decision process surrounding South Africa's energy futures requires a robust understanding of the water-energy nexus, especially under changing climatic conditions, recurring droughts, population growth, and increasing urbanization. The region targeted for energy development has historically supported rural populations and farming. This paper will provide an overview of energy/groundwater interdependencies in South Africa, discuss current and emerging approaches for developing baseline data, and provide practical insights from field investigations. The presentation will highlight the unique opportunity to leverage the global knowledge base related to unconventional energy development towards developing relevant, useful, and useable baseline data. The capacity to serve as a test-bed for new technologies and sensors will also be explored.

Anything Else Groundwater

Andrew Schmidt

Development of a Point Velocity Probe for in-Well Use

Trevor Osorno, Graduate Student
With the development of in-situ remediation technologies, the need for reliable estimates of groundwater velocities at local scales has increased.  The traditional approach of Darcy-based calculations is subject to uncertainties arising from scale limitations and estimations of hydraulic conductivity. This study presents a novel device designed to make groundwater velocity measurements in wells and to compliment velocity estimations based on Darcy calculations.  The device is a modification of the point velocity probe (PVP), which functions in a dedicated borehole without a well, and is called the in-well PVP (IWPVP).  The IWPVP is placed within the screened interval of groundwater monitoring wells.  Velocities are determined from travel times of tracer pulses travelling through channels inside the device. Preliminary laboratory experiments utilized a hand-cut well-screen installed in a homogeneous sand aquifer simulator to evaluate the viability of IWPVP designs. For initial experiments, the well-screen openings were aligned in the direction of groundwater flow, promoting flow directly through the probe. Preliminary results showed a linear relationship between calculated and measured velocities. The slope of the calibration line, describing the known vs. measured velocities, indicated that groundwater traveled through the IWPVP at a speed  about 15 times faster than ambient speeds (10–600 cm/day), with an R2 value of 0.9926. A two-dimensional model was constructed using COMSOL Multi-Physics to verify these initial results. The model estimated a velocity magnification factor (calibration slope) of about 11, in reasonable agreement with experimental results. Further work aims at improving model-experiment agreement through modifications to the experimental method and moving to three-dimensional modeling.  Future experiments will also be conducted using commercial well screens. On the basis of the early results, the IWPVP may become an inexpensive tool to use in conjunction with more traditional methods of assessing groundwater velocity, to gain insights concerning local flow rates in aquifers.

Downscaling GRACE for groundwater management in California's Central Valley

Michelle Miro
Groundwater is a critical component of the local, regional and global water cycle. It constitutes an important storage of water, often relied upon in times of drought and in arid environments. Sustainable planning and management of groundwater resources requires accurate information about trends in groundwater water levels and quantities. In much of the globe, however, this data is limited. The Gravity Recovery and Climate Experiment (GRACE) has already proven to be a powerful data source for regional groundwater assessments in many areas around the world.However, the applicability of this data product to more localized studies and its utility to water management authorities has been constrained by its limited spatial resolution (~150,000 km2). Researchers have begun to address these shortcomings with data assimilation approaches that integrate GRACE total water storage estimates into complex regional models, producing higher-resolution hydrologic results (~4,000 km2). The present study takes these approaches one stepfurther by developing an empirically-based model capable of downscaling GRACE data to a high-resolution (~16 km2) dataset of groundwater storage changes. The model utilizes an artificial neural network (ANN) to generate a series of maps of groundwater level change over the GRACE time period (2002-present) using GRACE estimates of variations in total water storage and a series of publicly available hydrologic variables. The San Joaquin Valley Groundwater Basin in California’s Central Valley serves as the initial case study. Overall, the present study achieves two main goals: 1) it integrates robust numerical methods from the field of systems analysis with geodesy and hydrology; and most importantly 2) it also represents an important application of GRACE data to a local-scale water management study, illustrating how widely available remote sensing data can be utilized by management authorities.

Estimates of Private Domestic Well Use in the United States: A Pilot Study in Oklahoma

James Weaver, Ph D
Private domestic wells are not subject to the testing requirements of the Safe Drinking Water Act and are susceptible to contamination by natural and anthropogenic contaminants.  For public health and planning purposes, the locations of high density of private domestic well (PDW) use need to be determined.  A key resource is the 1990 U.S. Census where the source of water was a survey question, which led to a nationwide estimate of PDW usage.  In this paper, methods are developed to estimate the areal density of PDW use in later years using readily accessible data including the 1990 census results.  Because of abundant data on PDW locations and public water supplies, Oklahoma was used for a pilot project.  Well logs reported to the Oklahoma Water Resources Board and the addition of housing units provided the means to update the 1990 census estimates.  Census results and housing unit data are available on the county, census tract, and census block group level. PWD density estimates were consistent among these scales, as were estimates based on reported well logs and net housing units.  The completeness of reported well logs was tested by counts from neighborhoods with known reliance on PDWs.  The results showed that a significant undercounting of logs exists, and the small scale of subdivisions relative to even census block groups caused the method estimates to be lower than subdivision PDW densities.  The estimates, however, indicate locations where high densities of PDWs may be expected.

Organic Contaminants in a tourist area: unexpected presence in the groundwater of the Yucatan Peninsula

Rosa Leal-Bautista, Ph.D.
Quintana Roo, which is located in the Peninsula of Yucatan, is the state with the nation's fastest rate of tourism development. In spite of this growth, the agricultural activity represents only 4.3% of the total revenue for the state. Just ten years ago, a proposal to study the impact of organic contaminants in this area was not deemed as important; however, results from studies at cenotes (sinkholes) and wells in the State of Quintana Roo within the Rio Hondo Basin (this agricultural zone is located on the border between Mexico and Belize) where there are approximately 22,000 Ha of sugar cane. Year after year, organic compounds are used to fertilize and protect the crops (including compounds such as organochlorides, organophosphates and pyrethroids) all of them which are classified as persistent organic pollutants (POPs) by the World Health Organization.  A second study evaluated the presence of POP’s within water supply wells within the Tulum área. The presence of POP’s were also confirmed in this second study. The carstic aquifer of Yucatan is highly vulnerable, and thus, the presence of POP’s in water supply wells is particularly worrisome.

We are concerned that POP’s are starting to show up not only in areas where the predominant activity is agricultura, but also, in new tourist developments. Additional care will be required to ensure that we can meet appropiate drinking water standards in this región.

KEY WORDS Yucatan Peninsula Mexico, Organic compounds, karst

Testing the Ideas of Walter White: An Estimation of Riparian Evapotranspiration Using Groundwater Upwelling

Jacob Kollen
In arid and semi-arid systems the riparian zone boarding a stream has high evapotranspiration rates compared to uplands. Evapotranspiration (ET) is difficult to estimate, but accounts for much of the water loss from landscapes. Walter White (1932) introduced a method using the diurnal fluctuation of groundwater depth to estimate ET. With the advent of accurate data logging pressure sensors, the White method has recently reemerged as an important strategy. A persistent challenge of the White method is knowledge of how much water is released per unit fall in the water table (the “specific yield”). Specific yield is highly variable, and there exists no validated method for its measurement. Our experiment will indirectly measure this term using two methods. The first method utilizes soil moisture probes, spaced 3cm apart along the vertical axis of a soil column to measure the volumetric change in water content accompanying changes in water table. Soil moisture and tension data will be used in conjunction with the Hydrus 1-D numerical model to estimate evapotranspiration. The second method is performing classical pump tests to estimate the in situ specific yield, and using this estimated specific yield term in the Walter White equation to estimate evapotranspiration. We will compare these groundwater based estimations of evapotranspiration against two micrometeorological data based estimations of evapotranspiration. The micrometeorological based methods are the ‘eddy covariance’ method as well as the ‘Penman-Monteith’ method. The deliverable by the end of this project will be a simple method to install and calibrate a groundwater table depth observation well to produce an accurate estimation of evapotranspiration and groundwater upwelling in areas with shallow water tables such as riparian areas.

Climate Change and Groundwater

Michael Wireman

Bayesian Model of Groundwater Change Using Satellite Data from the Grace Mission

Kimberly M. Slinski, MSc, PE
Groundwater drought, defined as the sustained occurrence of below average availability of groundwater, is marked by below average water levels in aquifers and reduced flows to groundwater-fed rivers and wetlands. The impact of groundwater drought on ecosystems, agriculture, municipal water supply, and the energy sector is an increasingly important global issue. However, current drought monitors heavily rely on precipitation and vegetative stress indices to characterize the timing, duration, and severity of drought events. The paucity of in situ observations of aquifer levels is a substantial obstacle to the development of systems to monitor groundwater drought in drought-prone areas, particularly in developing countries. Observations from the NASA/German Space Agency’s Gravity Recovery and Climate Experiment (GRACE) have been used to estimate changes in groundwater storage over areas with sparse point measurements. This study incorporates GRACE total water storage observations into a Bayesian framework to assess the performance of a probabilistic model for monitoring groundwater drought based on remote sensing data. Overall, it is hoped that these methods will improve global drought preparedness and risk reduction by providing information on groundwater drought necessary to manage its impacts on ecosystems, as well as on the agricultural, municipal, and energy sectors.

Characterizing Groundwater-Climate-Irrigation Dynamics in the United States

Sasmita Sahoo, Ph.D.
Groundwater is a vital and dynamic resource which needs to be properly assessed, especially in a changing climate. In the United States and many developing agricultural regions around the world, groundwater is a major source of irrigation. Unfortunately, climate change and increasing demand for freshwater has threatened its sustainability and significant depletion has been noticed in most principal aquifers across the United States. Therefore, the understanding of long-term impacts of climate variability and change is a key challenge in order to address sustainability management strategies at regional/global scales. This study analyzes groundwater level spatio-temporal variability with response to changing climate and surface hydrologic conditions. Several studies have investigated relationships between groundwater levels and large scale climate patterns, however we present a high resolution analysis of groundwater level with local precipitation, ET, stream discharge, and modeled irrigation consumption over the contiguous United States. Several statistical methods were applied to assess the influence of these variables on groundwater level fluctuations and to explain the spatio-temporal variance of the time-series. These methods include spectral analysis, coherence analysis, and cross-correlation analysis along with impact of lags in the hydrologic time-series. The results obtained through these statistical techniques show significant impacts of climate signals on groundwater levels and thus, improve our understanding of the aquifer system behavior as well as how water level sensitivity varies with forcing changes across the United States.

Coupling Brine Desalination with Carbon Sequestration to Produce Solid Carbonate Minerals

John Hoaglund, Ph.D. (geology)
Leftover brine from the desalination of brine groundwater, as well as seawater, can be used to sequester carbon into solid carbonate minerals, consuming the salt from the solution, thus eliminating brine discharge and increasing freshwater yields.  The process needs a source of CO2 such as from a power plant. The key is to use electrolysis of the saline water to raise hydroxide alkalinity, then to pass the CO2 through solution to convert the alkalinity into bicarbonate and carbonate components, conserving alkalinity but dropping pH. The bicarbonate and carbonate react with the salt cations to create the carbonate minerals. Hydrogen is created along with the hydroxide alkalinity in the reduction half of the electrolysis. The oxidation half of the electrolysis creates “reactive oxygen species” mostly chlorine based. These can be converted into acids using the hydrogen. The reaction is one of the most common in industry for creating these products, where salt and freshwater are mixed as raw materials. Several patents exist for the sequestration reactions, but few if any have been coupled to desalination. A scenario is presented for a proposed desalination facility on the grounds of an existing 900 MW natural gas power plant. A salt budget for the proposed desalination rate is shown to be sufficient to sequester all of the CO2 from the plant.

Development of a Conceptual Model for Evaluating Seawater Intrusion Under Sea-Level Rise Scenarios

Chelsea Jefferson, LG, LHG
Coastal groundwater aquifers used for water supply are subject to stress from increasing demand as well as the threat of seawater intrusion. This problem may be exacerbated by projected sea-level rise due to climate change. Here we evaluate the effects of sea-level rise on the municipal groundwater source of a Pacific Northwest coastal community. The objective of this study is to establish a conceptual model for this coastal groundwater aquifer for the purpose of evaluating seawater intrusion under sea-level rise scenarios. Local glaciofluvial geology, hydrogeology, and water chemistry data will be used to establish groundwater flow and its interaction with seawater. Analytical calculations, analytic element model, or numerical models will be used to test the conceptual model. Finally, the conceptual model will be used to make predictions of seawater intrusion (e.g. freshwater/seawater interface position and seawater wedge toe position) under a few projected pumping and sea-level rise scenarios.

Putting Your Well Field on a Low Salt Diet

John Jansen, P.G., P.Gp., Ph.D.
In the late 1970s researchers started to notice an increase in chloride and sodium levels in a few aquifers in the Upper Midwest and Northeast.  Since then, this trend has spread and intensified to the point where many wells in northern states have chloride levels over 100 ppm and rising.  Trend lines for many wells suggest that this will be a significant problem for many decades.

Road salt is the major culprit.  Depending on the aquifer, about 25% to 65% of the road salt applied ends up in groundwater.  Recent efforts have reduced salt application rates to some degree, but public expectations of snow free roads has resulted in total salt loading continuing to increase.  Decades of past heavy salt use will result in rising chloride and sodium levels for decades in many aquifers.

The keys to managing this problem are monitoring, prevention, and mitigation.  We present case histories from New Hampshire, New York, and Wisconsin where chloride impacts in shallow wells were tracked to road salt application, the lateral and vertical extent of contamination were defined by monitoring wells or geophysical methods, future salt levels were predicted, and mitigation methods have been proposed and implemented.

We present a salt budget that was calculated for a capture zone of a well field in Central Wisconsin that has a history of elevated sodium and chloride levels.  We compared the salt loading in the capture zones to recharge and residence time of the groundwater as a simple way to estimate future salt levels.  In this example the aquifer had short residence times and sodium and chloride levels were approaching steady state.  Several simple steps such as diverting snow melt from parking lots away from infiltration basins were successful in reducing sodium and chloride levels at specific wells.

Combined Remedies

Seth Kellogg, PG

A Simple Spreadsheet Model to Simulate the Natural Attenuation of Residual Hydrocarbon NAPL

John Wilson, Ph.D
At most sites, the rate of depletion of residual NAPL hydrocarbon is primarily controlled by the rate of aerobic biodegradation.  The actual rate of aerobic degradation is directly related to the diffusion gradient of oxygen in the unsaturated zone.  The lifecycle of the source zone will be controlled by the concentration of TPH, by the vertical distribution of the TPH, by the air-filled porosity that can supply oxygen by diffusion to the TPH, and by the fraction of the time that the TPH is above the water table and in contact with the soil gas.  The Vadose Zone Biodegradation Loss Model (VZBL) is a screening model that incorporates these site specific parameters and forecasts the lifecycle of TPH in the source zone.  The model forecasts the vertical distribution of TPH, the highest concentration of TPH at any depth interval in the vertical profile and the total amount of TPH remaining in the profile.  The VZBL model was applied to the former Hal’s Chevron Site in Green River, Utah.  A sensitivity analysis showed that the persistence of TPH was most sensitive to the air-filled porosity in the unsaturated zone, and to the distribution of the TPH compared to the distribution over time of the depth to the water table.  The presentation will offer practical techniques that can be used to estimate the air-filled porosity of the soil profile and attain a robust calibration of the VZBL model to a particular site. 

An Integrated Approach for Deducing Degradation Pathways at Sites Contaminated with Chlorinated Ethylenes

Todd H. Wiedemeier
Bioremediation, both natural and engineered, has emerged as the preferred remediation approach at many sites contaminated with chlorinated ethylenes. A number of prognostic and diagnostic tools are available, yet guidance documents to assist site owners in selecting the most efficacious bioremediation approach are limited. Although the value of substrate additions (i.e., biostimulation) to enhance contaminant degradation has been demonstrated, this approach may not be needed at sites where monitored natural attenuation (MNA) is sufficient to meet remedial goals. Both remediation costs and associated environmental impacts will increase as more invasive and aggressive treatment options are implemented. Therefore, selection of the most appropriate bioremediation approach can result in substantial savings of capital investment and operation and maintenance (O&M) costs. Furthermore, avoiding unnecessary aquifer amendments, such as substrates and inocula, minimizes undesirable secondary impacts such as pH changes, formation of greenhouse gases, and reduced aquifer permeability. On the other hand, aggressive bioremediation can significantly shorten remedial timeframes, thereby reducing O&M costs as well as long-term environmental impacts.

There is no clear guidance on how to choose between MNA, biostimulation, and bioaugmentation, a shortcoming that causes unnecessary expenses and potentially detrimental environmental impacts. A systematic framework was developed under a project sponsored by ESTCP. This framework represents an extension of the 1998 USEPA Technical Protocol for Evaluating the Natural Attenuation of Chlorinated Solvents and (i) incorporates quantitative information of Dehalococcoides mccartyi biomarker genes, (ii) uses Compound-Specific Isotope Analysis (CSIA) results, (iii) considers the contribution of abiotic transformation of contaminants, and (iv) recognizes that natural attenuation is an important component of integrated remediation strategies. This approach allows identification of existing degradation mechanisms and integrates groundwater geochemical and contaminant data with quantitative real-time PCR and CSIA information, along with the current understanding of biological and abiotic degradation mechanisms, to deduce degradation pathways.

Groundwater Remediation of Radionuclides Using a Novel Permeable Reactive Barrier: Laboratory and Field Studies

Mike Wireman
Zhovty Vody city, located in Dnipropetrovsk Oblast in south-central Ukraine, has long been an important center for the Ukrainian uranium and iron industries. Mining and processing activities during the Cold War resulted in poorly managed sources of radionuclides and heavy metals in waste rock, tailings storage facilities, and waste materials associated with hydrometallurgy production facilities. Widespread groundwater and surface water contamination has occurred, which creates a significant risk to drinking water supplies and aquatic and riparian communities that depend on the Zhovta River and the hydraulically connected shallow groundwater. Hydrogeologic and geochemical conditions in the vicinity of a large uranium mine tailings storage facility (TSF), a major source of contamination, were characterized to provide data to locate, design, and install a permeable reactive barrier (PRB) to treat groundwater contaminated by leachate infiltrating from the TSF.

Using a novel design and installation, the effectiveness of three different permeable reactive materials was investigated: zero-valent iron, phosphate material, and sulphate-reducing bacteria. To evaluate reactivity of the materials, batch and column experiments were conducted in the Kiev Polytechnic University laboratory using Zhovty Vody site groundwater. Reaction rates, residence time, and comparison with site-specific clean-up standards were determined. In the PRB installation, three separate rows of cylinders were filled with different permeable reactive materials, and groundwater sampling was conducted within and around the PRB. Key sampling parameters included field parameters, inorganic analytes, and contaminants of concern (radionuclides and heavy metals). Groundwater levels were also measured periodically throughout the study. Results of the study demonstrate the effectiveness of zero-valent iron and a mixture of sewage sludge, bone meal, sawdust, and water for remediating uranium contaminated groundwater when utilized in a PRB with this design.

Meeting the Critical Deadline While Implementing a Trio of Multi-Million Dollar Remedies: Collaboration Required

Jeffrey Bonsteel
Project implementation to meet an expedited schedule driven by regulations, access, and contractor coordination is an ongoing challenge for today’s environmental market. The remedial activities completed at the site of a former railyard exhibits successful implementation in an area heavily affected by utilities, multiple regulatory agencies, and a narrow construction window.

Remediation included multiple excavations, installation of a directed groundwater recirculation system over 12 acres of property, and the installation of a large electrical resistivity heating system. The team formed to implement the remediation included three consulting firms and input from the property purchaser’s consultant. Without collaboration, the objectives could not have been successfully implemented within the timeframe.

Construction occurred simultaneously during the Summer/Fall of 2014. At times, more than 100 construction personnel were on-site. The presentation will discuss the logistics of implementing the large remediation effort in a short timeframe. The process began with analysis of federal, state, and city permits and timing for completion of each. The permitting process was initiated while the remedial strategy was finalized. Areas of the site required two, or sometimes three, remediation activities to be implemented. Prior to construction, conflicts were identified and alternate solutions presented to streamline project implementation.

A site-wide construction manager was employed, while each remedial discipline also had an on-site construction manager. Technical teams for each remedial group worked to communicate scope, schedule, and project impacts. Weather delays, contractor coordination, and multi-trade union cooperation required schedule change and planning to meet the timeframe. Sequencing drawings were used to manage contractor progress, giving a visual representation of work, loading, and staging areas, and traffic patterns during construction activities. A comprehensive health and safety program with on-site supervision resulted in zero lost time incidents with over 30,000 man-hours worked.

Using Tracer Test Data to Calibrate a Complex Flow and Solute Transport Model

John Kondziolka
Successful calibration of groundwater and solute transport models to field data is critical to ensure their accurate predictive capability. Model calibration generally consists of two steps: a hydraulic flow model is calibrated using hydraulic field data, and then a solute transport model is calibrated using chemical field data. At a National Priorities List site in rural New England, a rare additional step was taken: tracer test data were used to significantly improve the calibration of both the hydraulic and solute transport models.

Three independent, conservative tracers were injected at three separate site locations into two different hydraulic formations. Downgradient concentrations were monitored for one year to develop breakthrough curves. Hydraulic heads and chemistry were monitored site-wide to collect traditional calibration data. The tracer data indicated the presence of a previously uncharacterized, localized preferential flow pathway through highly weathered bedrock.

MODFLOW and MT3DMS were used to simulate the hydraulics and chemical transport for the site and the preferential flow pathway. The three conservative tracers, along with chemical data for the five site constituents, provided eight independent datasets used to calibrate the geometric and hydrogeologic parameters of the preferential flow pathway. One constituent was the daughter product of another, which provided another check on the modeled decay rates. Particle tracking was used to calculate a site-specific dispersivity value.

Using the tracer test data to calibrate both models yielded more robust and accurate calibrations than could have been achieved using only traditional data metrics. Good breakthrough curve matches were achieved at a large number of downgradient wells for all eight solute transport models. The geometry of the preferential pathway conformed well with estimates of weathered bedrock thickness from boring logs, and the site-wide normalized root mean square error for hydraulic heads was less than 5% for all modeled times.

Ethics in the Groundwater Industry

David S. Lipson, Ph.D., PG

Groundwater Modeling

Jason R. House, CG, PG

Evaluation of excluding deficient models on multi-model analyses using AICc and KIC information criteria

Judith Schenk
AICc and KIC (Akaike second order and Kashyap information criteria) were compared in experiments where hydraulic conductivity and recharge were optimized for a set of experimental models using different boundary conditions and calibration data sets. Use of experimental models allows us to know “true” conditions, and thus evaluate procedures for improving model predictions. Multi-model analysis was conducted for each full model set and for a model subset which excluded deficient models. Objective criteria were used to identify deficient models. Model-averaged predictions based on AICc and KIC were compared to determine the impact of removal of deficient models. Using full model sets, AICc results were generally more precise than KIC, but less accurate such that some AICc model-averaged predictions did not include the true prediction within the confidence region. This condition persisted even with the removal of deficient models. Use of KIC to model-average predictions results in an extremely wide confidence region for some model sets, but precision was improved for most sets when deficient models were removed. The confidence region based on KIC increased for one experimental set after deficient models were removed. With a reduced model set, KIC results were generally more accurate but less precise than AICc. One exception was a model set where KIC was more precise, but in that case the true predictions were not contained within the KIC confidence region. Some model sets included only two or three models after deficient models were removed and in those cases AICc and KIC results were nearly identical.  In conclusion, for these experiments, the removal of deficient models did not change the quality of AICc model-averaged predictions, but KIC performance was improved. This is likely due to the inclusion of the Fisher Information term in the KIC criterion which will be unreasonably small for deficient models.

Update on Groundwater Modeling for the Protection of Egyptian Antiquities

Buvana Ramaswamy, P.G.
The construction of the Aswan High Dam on the Nile River in upper Egypt nearly five decades ago enabled a change from the historic flooding-draining annual cycle to perennial irrigation. Before the High Dam was built, the Nile floods not only brought nutrient-rich silts to the fields, they also washed away accumulated salts from the floodplain. After construction of the High Dam, farmers needed to apply more water to wash salts below the root zone to maintain production levels. This has caused a rise in the water table resulting in waterlogged soils in some locations.

In addition to the adverse impact on irrigated agriculture, waterlogging and salinization are also causing extensive damage to Pharaonic temples built in the Nile River valley. The antiquities are threatened by the increase in salinity of the groundwater contacting the foundation. To protect these antiquities from further deterioration, the Government of Egypt, through its implementing agency, the National Organization for Potable Water and Sanitary Drainage; the owner of the antiquities, the Ministry of Antiquities; and the United States Agency for International Development (USAID) have undertaken projects to lower the groundwater levels at antiquity sites.

At the 2013 NGWA Summit conference in San Antonio, Texas, CDM Smith presented the hydrogeological analysis and 3-dimentional DYNFLOW groundwater modeling that was conducted to support the design of a dewatering system in Edfu, Egypt. Dewatering systems have now been constructed in Luxor and Edfu based on the groundwater modeling for the sites.  These completed projects were recently recognized with a 2015 NGWA Outstanding Project Award. Currently, models are being developed for additional sites in Alexandria and Kom Ombo. This abstract proposes to provide a project update based on the new modeling and operations data from the constructed dewatering systems.

Groundwater Monitoring

Going with the Flow: Federal Funding Facilitates Progress for the U.S. National Ground-Water Monitoring Network

David R. Wunsch, Ph.D., PG
The SECURE Water Act, enacted in 2009, authorized the creation of the National Ground-Water Monitoring Network (NGWMN). Through the efforts of many non-federal stakeholders, and with the support of Congress, the NGWMN was appropriated $2.6M (through USGS) in federal funds in FY 2015. Congress is likely to provide appropriations through a Continuing Resolution for FY2016, which would keep the funds “flowing” for at least another fiscal year. Thus, the NGWMN implementation is bolstered by federal support, as well as ongoing initiatives that leverage existing monitoring programs and other innovative program support. The key to this success has been the coordination and communication among diverse participants, guided by the NGWMN implementation plan.

The NGWMN is a collaborative effort among federal, tribal, state, nongovernmental organizations; academia; and private industry volunteers. A brief progress report on NGWMN implementation will be presented, highlighting the commitment, coordination, and communication efforts of stakeholders. We will also present examples how participants are cooperatively leveraging federal support for the NGWMN, with guidance from the Subcommittee on Ground Water (SOGW), under the federal Advisory Committee on Water Information (ACWI). We will focus on: (1) adding new data providers, which is a specific high-priority goal for FY2016; (2) helping maintain and enhance participation of states already in the NGWMN; (3) collaboration between USEPA Regional Laboratories and data providers for testing water quality samples; (4) discussions with other federal agencies that maintain monitoring networks whose objectives and designs align with the NGWMN; and (5) initiating discussions with Tribal authorities, regional water districts, and other non-state data providers.

The progress report will include a summary of data providers as of the date of this presentation, along with anticipated progress for the remainder of FY2016 and FY2017, and future directions for the NGWMN. Details of these aspects of the NGWMN will be provided separately.

On the Development and Growth of the National Ground-Water Monitoring Network

Daryll Pope
The Subcommittee on Ground Water (SOGW) of the Federal Advisory Committee on Water Information (ACWI) is working to develop the National Ground-Water Monitoring Network (NGWMN). The Network is intended to provide water-level and water-quality data necessary for sustainable management of groundwater resources at a national scale. The core of the Network will be long-term sites. Data that are already being collected by various federal, state, local, or tribal agencies provide a source of potential sites for the network. These agencies can participate in the Network as data providers.

This presentation describes the progress of the Network growth to date. A federal appropriation to implement the Network became available in December 2014. Efforts are in place to enlist new data providers and add new sites to the Network. The U.S. Geological Survey (USGS) provided funds to several new data providers in 2015 through cooperative agreements. A solicitation in late 2015 will announce the availability of competitive awards for NGWMN data providers in 2016. A NGWMN Program Board will be established to work with the USGS and SOGW to assist in evaluation of proposals for the competitive awards for the Network. Concurrently, the NGWMN is working with USGS Water Science Centers to add appropriate water-level and water-quality sites to the Network. Adding sites from existing data providers like the USGS can occur quickly. However, adding sites to the Network from new data providers may take up to a year, because sites must be evaluated and communications must be established between various data systems. After the cooperative agreements are completed in 2016, the USGS, SOGW, and NGWMN Program Board can reevaluate the network based on the growth expected over the 2016-17 and then determine the next steps to develop the Network. 

South Platte River Groundwater Monitoring Network: Providing Data to Benefit Water Supply Management and the Public

Kevin C. Donegan
The Colorado Division of Water Resources (DWR) operates a groundwater-monitoring network designed to provide geographic, hydrogeologic and temporal coverage of water levels within the South Platte River alluvial aquifer.  The network was codified in the Colorado Revised Statutes in 2015 in response to recommendations from a study of the aquifer conducted by the Colorado Water Institute at Colorado State University.  That study was initiated in response to several groundwater issues in the South Platte basin including;  (1) the curtailment of irrigation wells not included in an augmentation plan, (2) increased recharge for the purposes of river augmentation and (3) properties negatively impacted by high (shallow) groundwater levels.

The existing network of 115 wells will be expanded to include additional wells measured by DWR along with wells in other monitoring networks operated by cooperating entities.  Ideally, wells to be added to the network will have long and uninterrupted periods of record, be located in areas that exhibit long-term trends resulting from human activities as well as short-term responses to those activities, and in areas relatively free of land use, surface-water diversion or artificial recharge.

The purpose of the monitoring network is to provide accurate groundwater-level data to be used in scientific investigations, to increase the public’s understanding and access to groundwater data, and to assist in water use and supply planning.  The data identify ambient groundwater conditions and provide for evaluation of the effects of natural and anthropogenic stresses, including climate-related stresses to the aquifer.  The South Platte River and its alluvial aquifer play critical roles in the domestic, agricultural, industrial and recreational water-supply businesses of Colorado.  An effective and efficient groundwater monitoring program will be an essential component for improved water-resource management of the South Platte River alluvial aquifer.

Groundwater Monitoring

Creating Baselines and New Insights Through Cloud-Based, Stakeholder, Groundwater Monitoring

Joseph Fillingham, Ph.D.
There is no such thing as static groundwater levels anymore. The pressures on vulnerable groundwater resources due to pumping and overuse are well known; however, better understanding and effective management continues to be a challenge due to both the technical and financial requirements of building a monitoring network capable of fully capturing the dynamic nature of groundwater systems on local and regional scales. Wellntel has stepped up to meet this challenge by introducing an affordable, non-invasive, cloud-based groundwater monitoring system which provides the well owner, the well servicer, the consultant, and/or the community the ability to deploy a monitoring system which provides access to data through an online, visual interface. The cloud system provides individual owners or communities the ability to monitor a network of wells on the same screen, while also allowing Wellntel to maintain the quality assurance and quality control of sensor measurements collected at frequencies on the order of hours. Directly engaging stakeholders through graphical representation of their groundwater resource in a common access interface fosters a collaborative environment focused on building understanding and new insights into groundwater availability and change. Established and developing Wellntel monitoring networks around the U.S. will be highlighted with a focus on how communities are utilizing Wellntel technology to develop a baseline understanding of groundwater dynamics for smarter, more engaged management.


Delaware Joins the National Ground-Water Monitoring Network

A. Scott Andres
The Delaware Geological Survey (DGS) has joined the National Ground-Water Monitoring Network (NGWMN) as a data provider. This new status is a logical outgrowth of the DGS’s service as an advisor to the Subcommittee on Ground Water (SOGW) and decades of operating and distributing groundwater data and interpretive products. DGS project staff have used NGWMN guidance criteria to select a subset of wells in use throughout Delaware for the national network, populated the NGWMN well registry, and created web services needed for the NGWMN portal to retrieve data.

DGS measures water levels as part of routine programs and special projects in 123 wells in two principal aquifers—North Atlantic Coastal Plain aquifer system and Piedmont and Blue Ridge Crystalline Rocks—and 13 major and local aquifers. An additional 50 wells operated by others have been evaluated for the network. More than 20 sites have nested monitoring wells completed in multiple aquifers to allow calculation of the potential for vertical flow between aquifers. Over 100 monitoring wells have 10 or more years of record. All of these wells have known construction details and nearly all have lithologic and downhole geophysical logs.

The DGS makes extensive use of automated water-level and salinity monitoring instruments to efficiently use limited resources, shorten the time needed to characterize the effects of pumping, and identify near real-time responses to climate and weather. Temperature and salinity data collected by these instruments will be added to the NGWMN water quality (WQ) network. The DGS has a long history with database systems. Starting with water-related schema and data vocabulary modeled after USGS WATSTORE in the 1980s, the system now manages data and metadata on lithologic and geophysical logs, rock and sediment samples, and distributes that data through web services in JSON and XML formats for consumption by the NGWMN.

Groundwater-Level Monitoring in Oregon

Karl C. Wozniak, MS, RG
The Oregon Water Resources Department (OWRD) currently measures periodic groundwater levels in about 1100 wells across Oregon. Measurement frequency varies from annual to bimonthly. Eighty-five of the wells are instrumented with automated equipment that records water levels at intervals of 15, 60, or 120 minutes. About 720 wells are associated with groundwater investigations that range in duration from several years to multiple decades. A core set of 380 wells belong to the State Observation Well Network (SOWN) which is designed to monitor changes in groundwater storage in the principal aquifers of the state over extended periods of time. As groundwater investigations mature or are completed, representative project wells are added to the SOWN. In this manner, the network becomes more robust over time. However, wells are periodically lost from the network because of changes in well-owner cooperation, changes in use that preclude the capture of static water levels, or changes in well construction that make measurements difficult or impossible. To avoid many of these problems, OWRD has embarked on a program of drilling dedicated observation wells. Thirteen wells were drilled during the 2014-2015 budget year and an additional dozen are planned for the 2015-2016 budget year.

In 2015, OWRD began participation in the U.S. Geological Survey’s National Ground-Water Monitoring Network. The principal goal of the network is to provide ready access to data from a set of selective wells in existing observation networks that reflect conditions in major aquifers of the nation. In Oregon, this will be accomplished by reviewing existing networks and selecting high-quality, long-term observation wells that best reflect seasonal and long-term water-level trends in the principal aquifers of the state. A review of the goals and progress of this project will be presented.

Integration of Water Resource Data from Multiple Sources to Facilitate Sharing and Decision Support

Eric Chiang, Ph.D.
A great number of public water sharing portals exist based on regional databases. To solve most practical problems, however, these regional databases need to be combined with local area databases to make defensible water resources management decisions.

To put both the public and local area datasets at the fingertips of investigators, we created the HydroDaVE (Hydrologic Database and Visual Explanations) managed service platform to store and serve local area data and combine them on the fly with data from public data portals.

HydroDaVE consists of three major components: (1) HydroDaVE Server with established web services to serve hydrologic, hydrogeologic, and climatic data that are stored in SQL databases; (2) HydroDaVE Manager (HDM) to remotely manage datasets on the HydroDaVE Server; and (3) HydroDaVE Explorer (HDX), a cloud-connected application with an intuitive map-based interface to visualize and analyze the data (e.g., multiple time-series charts, Piper and Stiff diagrams, geological cross-sections), and to create reports. Both HDM and HDX communicate with the HydroDaVE Server via the web services, which in turn interact with the backend SQL databases.

In addition to the localized data stored on the HydroDaVE Server, HDX can concurrently visualize time series data from the USGS Water Services and the Water Quality Portal of the NWQMC. Moreover, HDX visualizes a great number of gridded climatic datasets, including precipitation, daily minimum and maximum temperature from PRISM (OSU), NEXRAD (NWS), and CMIP3/CMIP5 (IPCC).

HydroDaVE is implemented at watershed-scale and provides integration of a variety of resource data. HydroDaVE is used by government agencies to manage their data and perform complex calculations. This paper provides an overview of the HydroDaVE design and examples of how HydroDaVE has been implemented in Southern California and subsequently used to design monitoring programs, resolve disputes regarding sources of contamination, and a groundwater model application.

Pressure Transducers - Common Data Issues and How to Avoid Them

Sonya Cadle, P.G.
Pressure transducers are used worldwide to collect data during groundwater monitoring and aquifer testing. These instruments have proven to be invaluable tools for hydrogeological analysis. However, the data collected can be of poor quality or may be rendered unusable as a result of common errors made during transducer selection, programming, installation, and download. In addition, improper transducer data manipulation can lead to erroneous conclusions. These problems have resulted in increased project costs and, in some cases, have resulted in distrust of transducer data collection.

Thousands of transducer data sets collected during aquifer testing and long-term groundwater monitoring were reviewed to distill key lessons learned that can be applied to any site.  When selecting a transducer, consideration must be given to factors such as the goal of the data collection effort, site-specific factors such as lithology and well completions, and the software interface of the instrument. Transducer programming, installation, and download must be planned in a fashion that makes successful data collection as easy and convenient as feasible, and the field staff should be trained to recognize and mitigate common problems they might encounter. Careful documentation is critical during the field effort. When problematic data are collected, the field documentation becomes a vital tool to successfully analyze the data despite its problems. A number of potentially catastrophic problems can be fixed during analysis if good field documentation is available.

Use of the National Ground-Water Monitoring Network to Evaluate Selected Transboundary Aquifer Systems

William L. Cunningham
Transboundary aquifer systems, by definition, cross a political boundary. The boundary may be international—but also can be a state or county boundary. Evaluation of aquifer conditions in transboundary aquifers often is time consuming because these data typically are in different data systems. Scientists and engineers must gather the data, assure data quality, and convert the measurements to a common datum prior to analysis. The National Ground-Water Monitoring Network (NGWMN) provides access to data of known quality in a common format, from disparate federal and state data systems transparently

The power of this capability is demonstrated by analyzing water-level data from three transboundary aquifer systems. First, water-level declines in the Lower Tertiary aquifer system (Montana/North Dakota/South Dakota) are presented. There are increasing demands on the aquifer system to support the water use necessary for increased energy production. Second, water-level declines in the Rio Grande aquifer system (New Mexico/Texas) are evaluated. Competing demands among these states and Mexico have resulted in water-level declines and subsequent lawsuits. Analysis of these data illustrates that the NGWMN provides a single, consistent dataset from which to evaluate the status of the nation’s aquifers and shared interstate groundwater resources. Because the NGWNMN and Canada’s Groundwater Information System adhere to international data-exchange standards, these same comparisons can be done across the U.S./Canada border. Analysis of selected transboundary aquifers between the United States and Canada also will be presented.

Groundwater Monitoring

An Animated Look at Groundwater Monitoring Data – Hydrographs in Map View

George Roadcap, Dr.
Water level hydrographs are used by hydrogeologist to help understand the behavior of an aquifer and the response to different stresses, however, the ability to separate out the spatial impacts from multiple stresses in the many hydrographs of a monitoring network can be very difficult.  To overcome this problem, we have developed a method to animate multiple potentiometric surface maps created at short time intervals (days or weeks) from pressure transducer data.  A MATLAB script is used to pick out data a given time interval, calculate means, and flag or fill in missing data. The water levels are then contoured using the finite-difference solver in MODFLOW. For the Mahomet and the Cambrian-Ordovician Sandstone Aquifers in Illinois, water levels from the observation wells were input as constant heads. Nodes for streams that are water table outcrops were also assigned constant head values. A uniform hydraulic conductivity was used for the entire aquifer, although the method is not sensitive to the specific value. No recharge or other flux boundary conditions were used. The thickness of the aquifer was used to capture the variation in transmissivity which can influence the results in areas where there are no data points. With this method the spatial changes in the potentiometric surface between measurements can be more clearly represented and the influence of different stresses more readily identified.

A numerical assessment of large screened monitoring wells on groundwater flow fields and solute distribution

Daniel Gomes
Proper design and construction of monitoring wells is essential to obtain representative samples for further analysis such as fate and transport modeling, risk assessment and feasibility of remediation projects. Monitoring wells with large screens have been used for many years to monitor groundwater, and although this practice has been largely replaced by smaller screens in recent years, several legacy, large-screened monitoring wells are still in use at many sites, leading to potential for cross-connection between aquifers and less than efficient in situ remedies. This paper conducts a number of simulations using groundwater flow, particle tracking and solute transport analysis to assess potential impacts of such wells in providing short cuts for solute transport across different layers. The detailed numerical experiments use Modflow and MT3D to simulate groundwater flow and transport through porous media with large screened monitoring wells. The study compares using Modflow’s Multi Node Well (MNW) package as well as zones of high hydraulic conductivity to simulate monitoring wells. A number of scenarios are analyzed including monitoring wells located in recharge and discharge areas; in areas with horizontal flow conditions, under isotropic and anisotropic conditions and heterogeneities. The study also compares results of the numerical analysis with actual data from real sites to shed light into the potential for cross connection.

Groundwater Quality

Water Quality Impacts of Tourism in Quintana Roo, Mexico

Katelyn Kane, MS geology student
The Yucatan Peninsula is the world’s largest connected karst cave system. The highly fractured limestone and scarce soil allows precipitation to rapidly infiltrate the groundwater system identified as the Yucatan Aquifer. The geology of the area also prevents the accumulation of surface water; as such groundwater is the only source of fresh water on the peninsula. The shallow Yucatan Aquifer allows contaminants to easily migrate into the groundwater.

The state of Quintana Roo, Mexico on the Yucatan Peninsula is economically dependent on the tourism industry. This study focuses on an assessment of ten locations where direct access to the groundwater is available.  Water samples are collected and tested for contaminants thought to be attributable to tourism. The goal of the study is to determine the main threats to public health.

The sites are tested for environmental constituents along with nutrients and various metals concentrations. In laboratory Total Coliform and E.coli fecal bacteria are tested for as a most probable number method and antibiotic presence/ absence tests are performed. The oxygen and hydrogen isotope values were also analyzed. DNA samples from each site were sent out for sequencing.  Samples were collected February, April, and June shortly after optimal times of tourist occupancy. Currently the plan is to take one last sample collection during the low tourist season of October. Initial results have shown high amounts of Total Coliform and E.coli fecal bacteria. The nutrient levels and metals are in low concentrations. The antibiotic tests thus far have produced negative results. The current findings of this study suggest that the primary contaminants are the bacteria.

Water Quality Sites and Data Management of Wells and Springs in Utah for the National Ground-Water Monitoring Network

Janae Wallace, M.S.
The Utah Geological Survey has established a groundwater monitoring network in Utah to contribute to the National Ground-Water Monitoring Network (NGWMN). We have created a widespread and comprehensive monitoring network consisting of approximately 100 wells and springs. The primary goal is to document water-quality changes over time by sampling annually.  Additional goals are to document water resources in a well administered and maintained database and integrate our state-level data with a national-level database.

Our site selection criteria follows guidelines of the Framework Document (SOGW); the primary site selection criteria are accessibility and representativeness of aquifers of interest.  Most sites are designated for trend monitoring. The priority of our network is to characterize the water quality of key aquifers in Utah.  To ensure high accessibility, most of the wells in our network are regularly pumped and privately owned.  Public supply sources are only included if it is the only representative, accessible well in the area or sampled infrequently for limited chemistry (i.e., only NO3 every few years), and only if the location is known and allowed to be disclosed.  We chose wells with sufficient aquifer information to ensure they are representative of the aquifer of interest.  We sample about 35 springs (smaller springs in mountain blocks/fronts to large regional springs).  Selected springs are accessible sampling points that represent major aquifer chemistry with no nearby well; large springs that represent the integrated aquifer chemistry for an entire drainage basin; or springs in mountain areas that represent chemistry of waters recharging the adjacent aquifers.

We are cooperating with the USGS to establish a connection between our network and the NGWMN, and providing the NGWMN with selected sites and related quality controlled data. We are currently establishing a database for our network to facilitate entry and integration of data to the NGWMN portal.

Groundwater Remediation

David S. Lipson, Ph.D., PG

Capping and Remedial Extraction of Groundwater in a Shallow Marine Shoreline Sequence at a Former MGP Site in Florida

Steven Sagstad, RG
Groundwater extraction wells were installed and tested to support a “hydraulic containment system” as part of an approved Interim Remedial Action Measure at a former MGP site which operated into the 1950s in Jacksonville, Florida. Site characterization indicate the presence of three sand layers separated by clay layers which compose a marine shoreline stratigraphic sequence. Groundwater contaminants (COCs) were delineated both vertically and horizontally within the three sand units which overly a relatively thin weathered limestone unit (not contaminated) encountered at a depth of 45 to 50 feet. COCs include VOCs, PAHs, arsenic, and cyanide.

Published hydraulic conductivity parameters for the three zones were unavailable for the three zones. Therefore aquifer testing of each sand zone was performed to estimate the hydraulic parameters for capture design. Based on aquifer test data collected from an array of observation wells, a transmissivity of 287 feet2/day (hydraulic conductivity of 31.8 feet/day) and a transmissivity of 464 feet2/day (hydraulic conductivity of 77.3 feet/day) were calculated for the intermediate and deep zones, respectively. The deep zone was determined to be hydraulically separated from the overlying layers, whereas the shallow zone appears hydraulically connected to the intermediate sand zone

Radius of capture analyses demonstrated that the extraction wells will contain the contaminant plumes for all zones. A pumping rate of 2-3 gpm for the intermediate zone extraction well and a pumping rate of 5-6 gpm for the deep zone well should be sufficient to contain the plumes on the on-site and off-site. The extracted groundwater is pre-treated with an oil/water separator, permitted and discharged into the local POTW, and the system is operated using PLC, transducers, pump controllers, and supporting equipment. The remedial system is currently operational and the site will be capped to limit recharge and further migration of contaminants

Groundwater Plume Analytics for Assessing Remediation Effectiveness

Joe Ricker, PE
Remediation effectiveness is evaluated using a variety of techniques that oftentimes focuses on the performance of engineered remedial systems. This presentation will focus on the evaluation of remediation effectiveness by evaluating the groundwater plume dynamics resulting from either anthropogenic or intrinsic remediation systems.

Groundwater plume analytics refers to the use of innovative evaluation techniques and methods to reliably and effectively communicate meaningful patterns in environmental data. Analytics relies primarily on graphical displays to communicate insight. Various case studies of remediation sites will be presented which highlight the use of plume analytics.

The plume analytics tools which will be presented include applications based on the Ricker Method® for plume stability analysis1. A plume stability evaluation allows the stakeholder to assess whether a contaminant plume is stable, decreasing, or increasing for a variety of metrics (i.e., area, concentration, mass, center of mass, and spread of mass). This allows better evaluation of remediation effectiveness, whether additional remedial action is necessary, if risk-based closure of a site is applicable, or whether natural attenuation processes may be occurring at a site. Outputs from the Ricker Method can be used as a basis for primary analysis and other plume diagnostic tools that allow the user to further evaluate and communicate groundwater plume dynamics. Examples will be presented that show evolving spatial differences (animated time sequence) within a groundwater plume resulting from remediation systems. Spatial differences are presented on both a magnitude basis and percent change basis.

Groundwater plume analytics tools have been used successfully to evaluate remediation effectiveness, demonstrate plume stability, cease operation of remediation systems, identify commingled plumes, identify unrealized source areas, and provide additional lines of evidence for natural attenuation.

New Dimensions in Groundwater Investigations: Using 3D Visualization Tools to Support Adaptive Strategies

Laurie Kellndorfer
Cross-sections have long been used to illustrate and analyze data as part of groundwater site investigations. However, it is difficult to update paper figures quickly. Interactive 3D visualizations build on paper cross-sections by allowing viewers to assess data, not just on the pre-selected cross-section, but also add and remove data sets as needed, spin the model, and interact with the data. CDM Smith has developed 3D visualizations for several large ongoing groundwater investigations and successfully used them as part of adaptive management strategies. This presentation will discuss our experience with a large, complex groundwater site. During the field investigation phase of the project, the 3D visualization model was updated on a daily basis with data collected by multiple drill rigs. It was then used to determine whether the desired depth interval had been reached. This reduced project costs by targeting drilling efforts. The 3D model was used to visualize the data collected during the field phase as it was being collected and in the context of previously collected data from a variety of sources. Multiple sources and types of data were visualized, including CPT (cone penetrometer test), MIP (membrane interface probe), geophysical logs, hydropunch and monitoring well water quality data, soil boring logs, regional stratigraphic interpretations, and existing paper cross-sections. Our experience with state-of-the-art 3D models demonstrates how this tool can be used to facilitate adaptive management for groundwater investigations, help target field efforts, ensure dollars spent produce maximum value, and enhance communication and teamwork between managers, geologists, and groundwater modelers.

Passive Removal of Chlorinated Volatile Organic Compounds from Contaminated Groundwater

Brian LaFlamme
The Hardage-Criner Superfund Site in central Oklahoma operated as a permitted disposal site from 1972-1980 and received over 20 million gallons of waste from industries in Texas and Oklahoma. A remedy component captures contaminated groundwater behind an interceptor trench using six recovery sumps.

A water treatment plant (WTP) using conventional air stripping technology and carbon polishing to remove chlorinated volatile organic compounds (CVOCs) before discharging the treated groundwater was in operation for over 12 years. The WTP was efficient at treating CVOCs to regulatory levels. However, rising operation and maintenance (O&M) costs, e.g., chemicals, electricity, and labor, necessitated an alternative for treating groundwater contaminated with CVOCs. The alternative had to remove CVOCs to below detection limits (BDL) for incorporation into the Monitored Natural Attenuation (MNA) remedy component, decrease O&M costs, and meet regulatory approval.

A series of field pilot tests, based on air stripping/carbon polishing technology, were designed to evaluate a Passive Aeration System (PAS) to demonstrate that CVOCs could be successfully removed to BDL. Based on the successful pilot tests, a full-scale test was implemented and demonstrated that the PAS could consistently remove CVOCS to BDL at flows up to 10 gallons per minute

Removal efficiencies and CVOC speciation from the pilot tests indicated that the PAS technology was a viable alternative to the conventional WTP. Analytical results from the full-scale test showed consistent analytical results of CVOCS that were BDL. The PAS was approved by the U.S. EPA and the Oklahoma Department of Environmental Quality as a permanent remedy modification to replace the conventional WTP.

The electricity savings alone using the PAS amount to more than $20,000 per year.  The PAS also employs air stripping and polishing steps but utilizes the sun and wind to remove the CVOCs without electricity or chemicals and with minimal O&M costs.

Groundwater Withdrawals and Resiliency

Desaturation of Sandstone Aquifers in Northeastern Illinois

Daniel Abrams, Dr.
In 2014-15, the Illinois State Water Survey conducted their largest synoptic measurement of heads in Cambrian-Ordovician sandstone wells since 1980. The study covered the northern half of Illinois. These observations were used to generate head contours of the sandstone aquifers. In 2014, drawdown from predevelopment conditions in northeastern Illinois was typically over 300 ft and exceeded 800 ft in the Joliet region. Three factors drove this large drawdown. First, demands for water from sandstone aquifers are much greater in northeastern Illinois than in the rest of the study region. Second, the sandstone aquifers are overlain by aquitards, which are low permeable materials that limit vertical infiltration of water. Third, the Sandwich Fault limits water flowing into the sandstone aquifers of northeastern Illinois from the south. Heads near the center of the cone of depression continue to have a decreasing trend.

The more severe drawdown in northeastern Illinois has resulted in local areas where heads have fallen below the top of the sandstone, known as desaturation. Desaturation of a sandstone aquifer can create a number of water quality and quantity concerns. The uppermost sandstone, the St. Peter, was observed to be partially desaturated in the areas of greatest pumping, even at wells which were cycled off. Simulations from a groundwater flow model indicate that the risk of desaturation will become more severe with increased future withdrawals.

Despite the relatively small demand for water throughout much of central Illinois, heads have been declining since predevelopment, likely due to the shale overlying the sandstone. This shale serves as an aquitard, minimizing vertical infiltration of groundwater to the sandstone. Sustained drawdown in this region could potentially induce flow from the southern half of the state, where water in the sandstone is highly saline and not suitable as a drinking water supply.

Estimating Hydraulic Properties with Stress-Specific Groundwater Models

Keith J. Halford, Ph.D.
Creating multiple simple, groundwater-flow models that simulate different stresses is a reliable approach for estimating hydraulic properties where different levels of discretization are required.  Multiple models are faster than a single integrated and complex model because specific problems are addressed with each model.  For example, steady-state flow, water-level declines from groundwater development, and responses to regional-scale aquifer tests frequently require different levels of spatial and temporal discretization. These requirements can be addressed quickly and correctly with three separate flow models with identical hydraulic-property distributions. Steady-state water levels and spring discharges can be simulated with a steady-state model. Water-level declines and spring captures can be simulated with groundwater-development and regional-scale, aquifer-test models.  Differences between all simulated responses and corresponding measured water levels, spring discharges, water-level declines, and spring captures are minimized simultaneously. Efficacy of this approach is illustrated with examples from the Death Valley region. Death Valley groundwater-flow models were created and calibrated rapidly where hydraulic properties are distributed with pilot points and geologic preferences are constrained with Tikhonov regularization.  Hydraulic conductivity and specific yield distributions were estimated with three numerical flow models that simulate different stresses and share common hydraulic-property distributions.

Importance, Distribution, and Character of the Nation's Brackish Groundwater Resources

Jennifer S. Stanton
Nontraditional groundwater sources, such as moderately saline (brackish) groundwater, are increasingly being used for drinking water, oil and gas extraction, power generation, and other uses to supplement or replace the use of freshwater. This demand is likely to grow as fresh groundwater resources continue to decline. Demand could grow especially rapidly in some parts of the country where climate changes result in hotter and drier conditions. Despite the current and future need for alternative water supplies, brackish groundwater was last assessed at the national scale almost 50 years ago. Since that study, substantially more hydrologic and chemical data have been collected that can be used to improve the understanding of brackish waters.

The U.S. Geological Survey is reassessing the alternative water supply potential of significant brackish groundwater resources. Preliminary results indicate that almost one third (2.2 million km2) of the continental United States is underlain by brackish groundwater (dissolved-solids concentration between 1,000 and 10,000 mg/L) within the uppermost 3,000 ft of the land surface. This evaluation is likely an underestimate of the total resource because available data for mapping the distribution of brackish groundwater are scarce in some areas, especially for depths greater than 500 ft below land surface where brackish groundwater is more likely to occur. Most of the known brackish groundwater is within in the Western Mid-Continent region. Other significant reserves of brackish groundwater largely are found in the Atlantic and Gulf Coastal Plain, Eastern Mid-Continent, and Southwest Basins regions. The ability of brackish aquifers to produce at least 100 gal/min of water was greatest in the Southwest Basins (80 percent of wells) and least in the Western Mid-Continent region (8 percent of wells).

Managing Groundwater in Virginia's Coastal Plain: Actions and Initiatives Since 2007.

Craig Nicol
Virginia continues to see declining groundwater levels, increase in chloride concentrations, land subsidence, well interference and loss of storage to its confined aquifers system in the Coastal Plain.  With over a hundred years of research and monitoring in Virginia, documented concerns and trends lead to well capping laws, the creation of a Ground Water Management Act and a regulatory framework for the establishment of management areas and permitting activities. However, 2010-2020 may be the most important decade for Virginia to decide on actions that result in long term sustainability of groundwater in the coastal plain aquifer system.    

Since 2007, the Virginia Department of Environmental Quality has been actively implementing goals developed through strategic planning to reduce current use, promote greater water conservation measures, increase hydrogeologic understanding and modeling capabilities that assist or promote innovative ways to manage groundwater in Virginia.    

To help meet these objectives the following actions have been taken since 2007:

  • Conducted a Peer Review

  • Expanded internal resources and associated budgets for characterization efforts through legislative amendments

  • Passed revised regulations and expanded a Groundwater Management Area  

  • Revised guidance documents and policies

  • Migrated the new Virginia Coastal Plain and Eastern Shore Models into use  and then  integrated with new geo-referenced content management system as VAHydro 

As a result of those initial actions VADEQ has now embarked on the next step, the Virginia Coastal Plain Groundwater Initiative. The initiative includes modeling activities to evaluate the optimization of proposed reductions, an investigation into the economic impacts associated with those proposed reductions and a 2015 legislative action resulting in the creation of the Eastern Virginia Groundwater Management Advisory Committee.  The Committee has been tasked with examining options for developing long-term alternative water sources and management structures along with other actions that may enhance the effectiveness of groundwater management.

Groundwater Withdrawals and Resiliency

A National Groundwater Model with Improved Resolution of Deep Groundwater Dynamics

Tess Russo, Ph.D.
Large scale estimates of groundwater dynamics are limited by the model structure, data availability, and aquifer heterogeneity. Previous continental-scale groundwater studies have used near-surface soil or bedrock geology to infer shallow aquifer properties, and homogenized or omitted the deep aquifers which are most heavily relied upon for water supply. To estimate groundwater availability and change in shallow and deep aquifer systems, we used historical USGS aquifer water level data, and estimates of storativity, layer thickness, and permeability, from calibrated regional groundwater models. Groundwater recharge was estimated in two ways: (1) using a land-surface hydrologic model to estimate net recharge, and (2) using statistical parameterization estimating recharge as a function of precipitation, aquifer lithology, and land use. Where available, we use recharge estimates from published studies to inform our modeling. The gridded model structure has a surface layer into which net recharge is added. Subsequent lower layers represent known major aquifers and confining units, or an equivalent representation of multiple layers. Saturated flow between layers and across grid cells is determined based on head and an effective hydraulic conductivity factor which is a function of layer thickness and contact area. Pumping withdrawals were estimated using agricultural crop water requirement models, municipal data, and USGS water use reports. The model was calibrated using hydrologic data between 1950 and 2010, and will be used to optimize land use and urban development within the country under future climate and economic scenarios.

Basin Wide Groundwater Model of the Rialto-Colton Basin for the Source Area OU Remedy for the RFF Superfund Site

Steve Luis
ERM and ENVIRON developed a basin-wide groundwater flow model (2012 Model) for purposes of designing the hydraulic control remedy of the Source Area Operable Unit (SAOU) at the Rockets, Fireworks, and Flares Superfund Site in Southern California. The principal contaminant, perchlorate, has impacted municipal supply wells. The principal objective of the project was to perform a comparative evaluation of potential extraction well locations and pumping rates while minimizing pumping rates necessary to achieve hydraulic capture under a wide range of hydrologic conditions in the RCB.

The RCB is an alluvial basin located in southern California that is bounded by faults and bedrock outcroppings. The majority of water inflows to the RCB are in the subsurface across fault boundaries. The majority of outflows consist of groundwater extractions for municipal water supply. All groundwater extraction in the RCB, including that of the SAOU, is subject to operational constraints imposed by the 1961 RCB Decree as well as the capacity of the water treatment and supply infrastructure. Given these considerations and the project objective, it was necessary to begin model development with quarterly water balance of the RCB. The water balance components were compiled for 42 years (1970-2011) using extensive data collected from various water purveyors. The RCB water balance builds upon previous models of the RCB, as well as neighboring basins. However, it was also necessary to develop new parameterizations due to the complex relationship between inflows and stratigraphy in the RCB.

 

Based on predictive simulations, one extraction well was located such that a high degree of hydraulic capture was predicted.  The basin-wide model development approach, with its emphasis on a reasonable water balance, extensive calibration, and thorough examination of potential extraction options made it possible to optimize SAOU remedy pumping in the near term as well as anticipate potential future pumping requirements.

Mapping Potential Groundwater Recharge Zones in Mexico Using a GIS

Luis Marin
We developed a Decision Support System/Decision Support Tool using a seven layer GIS based on data from the Instituto Nacional de Estadística, Geografía e Informática (National Institute for Statistics, Geography and Informatics;INEGI) which is being used by the Prograna Nacional de Reforestación y Cosecha de Agua (National Reforestation Program). The aim of the DSS/DST is to help identify potential infiltration/recharge areas for reforestation and for enhanced infiltration/recharge areas for the main watersheds of Mexico.

As more than 80,000,000 Mexicans depend on groundwater as their sole source of water, mapping potential infiltration/recharge zones is critical for Mexico. We are partnering with UCIA-CICY (a CONACyT Research Center) to develop a GIS-based mehtodology to identify potential Hydrogeologic Reserve Zones. Integrating both tools may allow Mexican policy makers to have a tool that will help with groundwater management in Mexico.

Using Recharge and Recovery to Meet Water Management Objectives in Arizona

Sharon B. Megdal, Ph.D.
Central Arizona water suppliers and users utilize Arizona’s well-designed statutory framework for water storage and recovery to meet water management objectives.  Water banking, other long-term water storage, annual storage and recovery, and groundwater replenishment programs continue to be important vehicles for (1) preparing for future Colorado River shortage conditions, (2) providing a mechanism for meeting 100-year assured water supply requirements, and (3) offering an alternative or supplemental approach to treating surface water and effluent.  The presentation will provide an overview of Arizona groundwater storage and how integral these storage and recovery programs are for meeting Arizona’s water management objectives.  The focus will be on the region served by the Central Arizona Project (CAP), a large constructed project that conveys Colorado River water to Arizona’s metropolitan areas, such as Phoenix and Tucson.  The CAP will experience significant water supply curtailment when a Colorado River shortage is declared by the U.S. Secretary of the Interior.   The presentation will discuss achievements realized during the 20 years since passage of the Underground Water Storage Act, as well as the challenges associated with groundwater use in Central Arizona.

Groundwater and Energy

Andrew Schmidt

An Analysis of Water Use in Hydraulic Fracturing Vs. Other Uses

Steven P. Musick, B.S., PG
It has often been said that hydraulic fracturing uses a relatively small amount of water when compared to other uses. Clearly, high volume horizontal well hydraulic fracturing is a relatively minor user of water at the national level, accounting for less than 0.1% of water use when compared to other water uses such as irrigation and public water supply. However, the question remains as to whether or not this ratio of usage between sectors remains consistent down to the local level. In this presentation we will discuss the findings of a comparative analysis of water use in the sectors of irrigation, public water supply, and hydraulic fracturing at decreasing geographic scales in three oil and gas producing states (Texas, Pennsylvania, North Dakota) to determine whether or not the relationship between water usage in these sectors remains relatively static from national to county levels. Further we will evaluate the relative use between states to determine what effect substantial reuse of water for hydraulic fracturing has on overall water use when compared to other sectors.  To analyze water usage across the three sectors, data from USGS water use publications and the FracFocus© chemical registry were utilized. Where unique state or regional conditions might apply, additional information from state regulatory agencies was utilized to ensure that water usage was consistent with agency figures.

An Overview of EPRI Research to Solve Groundwater Challenges Faced By the Electric Power Industry

Bruce Hensel
The Electric Power Research Institute (EPRI) performs research to support all aspects of the electric power industry, from generation to transmission to environment. EPRI environmental research related to groundwater over the past 30 years has included basic research to better characterize and understand inorganic groundwater chemistry at coal combustion residual sites, organic groundwater chemistry at MGP sites, and radionuclides in groundwater at nuclear facilities. Applied research has focused on topics such as groundwater data analysis methods, corrective action, and tools such as groundwater modeling and data management software. This presentation will summarize EPRI’s groundwater research programs, including groundwater assessment and corrective action at coal combustion residual sites, former manufactured gas plant sites, decommissioned fossil power plant sites, and active and decommissioned nuclear power plant sites, as well as establishment of the EPRI Groundwater Resource Center.

Numerical Analysis of Groundwater Quality Impacts from Hydraulic Fracturing Wellbore Leakage

Amy Rice, Ph.D. Candidate
The development of directional drilling and stimulation of reservoirs by hydraulic fracturing makes it economically feasible to recover unconventional oil and gas resources from shale formations, coal beds, and tight sand reservoirs. Hydraulic fracturing presents a set of water-quality challenges, including increased competition over water resources and the potential for air, surface water, and groundwater contamination. In this project, we use a three-dimensional, multiphase, multicomponent numerical model to investigate hydrogeologic conditions that could lead to groundwater contamination from a leaking hydraulic fracturing wellbore. We find that groundwater contamination resulting in impact to human health and the environment varies as a function of heterogeneity in subsurface permeability. Also, we describe a scenario where methane may serve as a precursor to contamination of drinking water aquifers by brine.

The National Oil, Gas and Injection Well Gateway

Joseph Lee, PG
The Ground Water Protection Council (GPWC), with the support of the U.S. Department of Energy and The Energy Information Administration have developed the National Oil and Gas Gateway.  The Gateway is  the first public website where well level data from all participating States can be viewed, aggregated and retrieved from one location.  Prior to the development of the Gateway, the only way to see a national picture of well level data was to visit each producing State’s website and consolidate the data or purchase commercial databases.  With the Gateway, this data is available via one websitts.

The Gateway website is an invaluable tool for government, industry and financial analysts, scientific researchers, and others who want a simple way to obtain and analyze well level data across the United States. 

Benefits of the Gateway for States include a more robust portrait of State activity within a national context, data to view intra- and inter-basin activity in adjoining States, fewer staff hours spent responding to external inquiries, and increase transparency.

Groundwater and Energy

Michael Wireman

Evaluation of Hydrogeologic Data Associated with USGS Areas of Potentially Induced Seismicity

Caitlin Barnes
The United States Geological Survey (USGS) identified 17 U.S. locations experiencing an increase in seismicity, which may be potentially induced through industrial fluid injection. These locations span across seven states, which vary in geological setting, industrial exposure and seismic history. Comparing the research across the 17 locations reveals patterns for addressing induced seismicity concerns, despite the differences between geographical locations. A critical need exists for hydrogeological data in order to determine potential causes and manage risk. Most induced seismicity studies evaluate structure and seismic data, but the inherent triggering mechanism is the transmission of  pressure pulses. This research evaluates whether data are available in these locations to generate hydrogeologic predictions, which could aid in managing seismicity. After analyzing peer-reviewed research within the 17 locations, this research confirms a lack of site specific hydrogeologic data for at risk areas. Obtaining hydrogeological data could lead to better risk management for injection areas.

Feasibility Evaluation of Using Open-Loop Ground Source Heat Exchange in a Coastal Aquifer

Min-Ying Chu, Ph.D., P.E.
The ongoing California drought continues decreasing hydropower generation and increasing power generated by natural gas. Because energy use in residential, commercial and institutional buildings account for a significant portion of energy consumption and carbon emission in California, an energy efficient measure to service various heating and cooling loads of a building is desirable. It has been recognized that use of ground source heat exchange (GSHE) systems has great potential in reducing carbon emissions, enhancing water conservation, and providing cost saving relative to traditional heating and cooling methods. In this presentation, we describe an integrated approach to evaluate the feasibility of a possible open-loop GSHE system for a mixed commercial and residential development project in the San Francisco Bay area.

The open-loop GSHE system was assumed to use groundwater recirculation to meet all cooling and heating demand. The hydrogeological framework of the study area was based on published literatures and review of more than 60 water wells and borings in the study area. The groundwater flow field and thermal transport was evaluated using the MODFLOW and MT3D modeling tools under different recirculation configurations. To account for the thermal energy interaction between the injection and extraction wells, the injected groundwater temperature was based on time-dependent thermal loading and simulated extracted groundwater temperature. The projected magnitude and pattern of heating and cooling demand were repeated for 12 years to evaluate the long-term system performance.    

The system feasibility was assessed using the following criteria: (1) ability to service the peak thermal load, (2) ability to maintain the temperature of extracted groundwater within the range of effective heat exchange, and (3) possible thermal impacts to groundwater receptors as thermal energy migrates away from the site.

Influence of Hydraulic Fracturing on Leaky Abandoned Wells

Joshua W. Brownlow, PG
The association between hydrocarbon-rich reservoirs and organic-rich source rocks means unconventional oil and gas plays usually occur in mature sedimentary basins – where large-scale conventional development has already occurred. Abandoned wells in proximity to hydraulic fracturing could be influenced by increased fluid pressures and corresponding newly generated fractures that directly connect to an abandoned well or to existing fractures connected with an abandoned well. If contaminants migrate to a pathway hydraulically connected to an abandoned well, upward leakage may occur. Potential effects of hydraulic fracturing on upward flow through a leaky abandoned well were investigated using numerical modeling. Several factors that affect flow to leaky wells were considered; proximity of a leaky well to hydraulic fracturing, flowback, production, and leaky-well abandonment methods. The numerical model used historical records and available industry data for the Eagle Ford Shale play in south Texas. Numerical simulations indicate upward contaminant migration could occur through leaky converted wells if certain spatial and hydraulic conditions exist. Flow was constrained to the stimulated reservoir volume of the shale. Magnitudes of upward flow through leaky converted wells increased with proximity to hydraulic fracturing, but decreased when flowback and production occurred. Fluxes ranged from approximately 0.086 to 0.006 m3 d−1 for hydraulic fracturing scenarios. Detection of contaminants in shallow aquifers is challenging, and upward fluxes through leaky abandoned wells could be unrelated to hydraulic fracturing. The results also underscore the need to evaluate historical activities.

Groundwater/Surface Water Interaction

Rory Cowie

A Proposed Approach to Sustainable Groundwater Extraction Based on Surface Water-Groundwater Interaction

Michael Tietze, PG, CEG, CHG
Understanding the interaction of interconnected groundwater-surface water systems is fundamental to sustainable water resources management; however, surface and groundwater management decisions must address fundamentally different issues and time frames. Surface-water management must respond to short-term climatic variations, flood control, streamflow requirements, and changes in water demand and availability. Groundwater systems typically respond to recharge and extraction over decades or longer, requiring longer-term management decisions. We present an approach to groundwater management based on management zones that recognize the physics of surface water-groundwater interaction, but honors these inherently different management requirements. Examples are provided for the Stanislaus, Tuolumne, and Colorado Rivers in California.

The amount and timing of streamflow depletion depends on pumping rate and duration, well location relative to the stream, aquifer diffusivity, streambed conductance, and vertical flow impedance within the aquifer system. These principles were used to develop proposed groundwater management zones around aquifer-connected streams by simulating extraction from theoretical wells at various depths and distances from the streams, under a range of stream and aquifer conditions. Simulations were carried out using STRMDEPL08, an analytical streamflow-depletion model developed by the USGS, and validated using existing numerical groundwater flow models constructed using the USGS MODFLOW code. Simulated surface water depletion by shallow wells near streams closely mimics applied pumping rates and timing, which supports groundwater management in tandem with surface water as is currently done in California for pumping from a “known and definite channel.” Pumping from greater distance or depth causes an attenuated hydrologic response in both amplitude and time. Groundwater management zones are thus proposed based on distance to the affected stream, depth of the well’s screen interval, and timing and duration of predicted streamflow depletion, considering the amount of seasonal and long-term streamflow depletion that is tolerable under existing ecological and water rights requirements.

Estimating Groundwater Discharge and Contaminant Loading to Newtown Creek, Brooklyn/Queens New York

Jeffrey J. Frederick, RG, CPG
Estimating the amount of groundwater discharging to a surface water body is a fundamental underpinning for establishing a comprehensive CSM. The Newtown Creek Superfund Site is a tidal estuary in an urban setting. Newtown Creek, a tributary to the East River and the New York Harbor Estuary, is 3.5 miles long and 200 feet wide, has five tributaries, and is surrounded by a prolific porous media aquifer. The creek has a complex hydrogeologic history and has been the recipient of historical and ongoing releases of contamination. Determining the groundwater discharge to the creek is the first step is assessing the importance of groundwater as a contaminant loading mechanism to the creek. Several methods were used to evaluate groundwater discharge to the creek including Thermal Imaging, Trident Probes, UltraSeeps seepage metering, and intrusive investigations using a barge-mounted Waterloo Profiler. Groundwater samples were collected and heads were measured at multiple depth within and below the sediment. This talk will discuss the methods used to collect the groundwater discharge and contaminant load information and the analyses that were undertaken to determine the importance of groundwater as sources of fresh water and contaminants to Newtown Creek. The analyses showed that groundwater is a significant source of contaminant loads, second only to loads contributed from NAPL migration.

Flow of Groundwater at the Interface with Permafrost

Sairavichand Paturi
The largest contaminated groundwater plume in Alaska exists in a discontinuous permafrost aquifer in the area of North Pole, Alaska. The aquifer is contaminated with sulfolane; a compound used in the refining of petroleum. As a part of remediation a relatively large monitoring well network has been installed to track the dispersion of the contaminant. Monitoring results revealed that the plume is much more dispersed in the lateral direction representing the contaminant presence in suprapermafrost and subpermafrost portions of the aquifer. Previous studies of this aquifer has shown that contaminant thawed through taliks exists in different areas of the plume, providing connectivity between the sub and suprapermafrost portions of the aquifer. These taliks are providing the pathways for sulfolane to reach the subpermafrost portion of the aquifer and possibly retract into the suprapermafrost portion of the aquifer. The objective of this study is to determine the pathway for sulfolane to reach the subpermafrost portion of the aquifer; the vertical and horizontal flow gradients in key locations of the plume are evaluated. Asymmetrical errors in water level measurements due to the frost heave and thaw settlement of monitoring wells are reduced by Monte Carlo analysis. A three dimensional model with flow vector visualization of groundwater with discontinuous permafrost has been created. The effect of seasonal variability in the flow pattern provided new understandings of the contamination at plume boundary. With a precise flow vector visualization, seasonal variability and measured concentrations of sulfolane, a cutting-edge groundwater flow pattern in discontinuous permafrost regions has been determined. This is the fundamental study that has investigated groundwater flow at the interface with permafrost bodies in areas of discontinuous permafrost. Understanding this interaction is key to our understanding of contaminant transport, aquifer recharge, and resource development in subarctic environments.

Groundwater As a Loading Mechanism in Two Tidal Estuaries, Gowanus Canal and Newtown Creek, New York, New York

Shane McDonald, CPG
Sediment site investigation often focus on point source discharges and internal redistribution mechanisms such as prop wash and erosion as primary contaminant loading mechanisms in tidal estuaries.  Groundwater loading was assessed at the Gowanus Canal and the Newtown Creek Superfund sites by NYCDEP and the results compared to other studied loading mechanisms such as Combined Sewer Overflows (CSOs) and ebullition facilitated NAPL migration.  The results show that groundwater is an important mechanism that contributes significant loads of contaminants to the system.  Groundwater’s contaminant loads dwarf loads contributed by CSOs, however the groundwater loads are not as large as those contributed by ebullition facilitated NAPL migration (where it was quantified in Newtown Creek).  Evidence of groundwater’s contaminant contribution was established by comparing mass fractions of polycyclic aromatic hydrocarbons (PAHs) in groundwater, surface water, CSOs and sediment in Gowanus Canal, which showed a direct correlation between groundwater and surface water total PAH make up, while CSOs were found to have a significantly different PAH make up.  These analyses show that groundwater loading and ebullition assisted NAPL migration must be understood to have a comprehensive conceptual site model.

Groundwater/Surface Water Interaction

Jason R. House, CG, PG

Channel Erosion, Sediment Yields, and Water Supply: A Central Texas Case Study

Stephen Norair
Water demand in Central Texas is expected to rise significantly due to a projected 76% population increase by 2060. Investigations of groundwater and surface water are increasingly important for decision makers that need to balance water supply with sustainability. For surface water sources (e.g., lakes, rivers), two factors considered in determination of sustainability are: (1) upstream channel erosion rates, and (2) accumulation rates of sediment downstream.  In this study, a combination of dendrogeomorphic, submerged jet testing, laser scanning, and SWAT-DEG modeling techniques are integrated to determine past erosion rates and predict future channel behavior for two stream channels in Central Texas. Dendrogeomorphology estimates past erosion rates from trees with exposed roots due to anatomical changes that occur after roots are uncovered by channel erosion. This method is valuable because historical erosion data can be gathered in previously unstudied locations. The erodibility of channel soils are determined using the submerged jet test. By subjecting an undisturbed sediment core from a stream channel to a jet of water at a known velocity, its resistance to scour erosion can be determined. A fabricated laser scanner was also developed for this project. This device uses three relatively inexpensive range-finder lasers to generate a centimeter-resolution channel cross sections. It also provides a labor-efficient method to monitor future channel morphology changes. These data can then be used to calibrate and validate SWAT-DEG, a channel degradation model that predicts the amount of stream bank erosion occurring within a reach. By integrating these measurement, monitoring, and prediction techniques channel change and sediment yields can be calculated to determine how much water is available within lake and reservoir sources, thereby giving water managers the information needed to determine how to sustainably utilize ground water resources.

Decision Making Under Uncertainty: A New Approach to Decision Making in a Multi-Model Environment

Timothy Bayley
A primary role of hydrogeologic models is to support decision making.  However, the uncertainty inherent in these models complicates their use as decision making tools.  Increasingly, multimodel methods are used to develop more robust predictions of future system states and include measures of model associated prediction uncertainties.  Given a set of predictions from a multi-model analysis, one must undertake the process of choosing a prediction to guide decision making.  Outputs from a multi-model analysis are often reduced to single models (e.g., maximum likelihood, worst case), or averaging approaches (e.g., Bayesian model averaging, likelihood weighting) when used to make hydrologic decisions.  With the exception of the worst case method, these approaches consider the range of model predictions, but they do not consider the implications of different predictions for decision making; a consideration that is accepted as standard in formal quantitative risk analysis.  This talk presents an approach that considers the outcomes of decisions based on multi-model hydrologic predictions and demonstrates that it can lead to improved decision making and engineering design under uncertainty.   Examples will be presented from synthetic case studies that illustrate the validity of the method and from real world groundwater flow and transport studies that demonstrate the practical application of the method.

Spatial Quantification of Groundwater/Surface-Water Interaction Using the Flir Infrared Camera

Joe C. Yelderman Jr., PhD, PG
Numerous studies have used temperature to detect the locations of groundwater/surface-water interaction. However, few studies have used temperature to quantify the spatial area of groundwater-influenced temperatures in surface-water bodies. The FLIR infrared camera provides the ability to detect and quantify temperature differences in surface-water bodies caused by groundwater discharge. This study used data from the FLIR camera in conjunction with field measurements of temperature and specific conductance to map the areal influence of spring discharges to Salado Creek in central Texas during several different settings of temperature contrast. The results may provide important information to develop management strategies for protecting the threatened Salado Salamander, Eurycea, chisolmensis which inhabits this groundwater/surface-water interface.  The location and spatial extent of groundwater-dominated zones, mixing zones, and stream-dominated zones were mapped during several temperature contrast settings. Data indicate that the size of the influenced area is affected by relative flow volumes between spring and stream, seasonal temperature differences, geomorphic positions of discharge points, and turbulence in mixing zones.

Sub-Regional Groundwater Flow Modeling of the Upper Big Blue Basin Using the MODFLOW-OWHM Farm Process

Kurt Zeiler
The Upper Big Blue Natural Resource District and Brown and Caldwell constructed and calibrated a three-dimensional subregional groundwater flow model of a portion of the Big Blue River Basin in southeastern Nebraska using MODFLOW-OWHM including the Farm Process Version 3 (FMP3) (Hanson et al., 2014).  The Farm Process simulates the interactions of agricultural processes with groundwater and surface water including crop uptake from soil water (variably saturated to fully saturated), crop demand-driven pumping of groundwater and/or diversion of surface water for irrigation, and return flows to both groundwater as deep percolation and surface water as surface runoff.  The subregional model simulates the period from 1950 through 2010 with the six different crop types grown within the model domain with the crop mix and irrigation patterns determined each decade based on National Agricultural Statistics Service data and information from the Nebraska Department of Natural Resources groundwater well database.  In the subregional model the Farm Process is linked to the Multi-Node Well Package to provide irrigation from groundwater, the Unsaturated Zone Flow Package to simulate the timing of deep percolation reaching the water table, and the Streamflow Routing Package to receive both surface water runoff and baseflow arising from groundwater.  The model was calibrated over the simulation period to observed groundwater levels at 81 water level monitoring locations, and to both total gauged streamflows and estimated stream baseflow values at 4 stream gauging locations. The model is currently being used as a tool to delineate “10/50 zones”, which are those areas in which pumping a groundwater well over a 50 year period is predicted to result in a 10 percent or greater reduction of baseflow in adjacent streams. Future planned work includes construction and calibration of a regional-scale model of the Blue River Basin within Nebraska.

Taming the Tumalo: A Damned Dam Repurposed for Recharge

Kelsey Harpham
Built in 1914, the “Tumalo Project” was proclaimed an utter failure upon completion. As the reservoir filled with water diverted from Tumalo creek, sinkholes developed in the reservoir floor and every last drop of captured water disappeared into the ground. Considerable research has been undertaken on the social and political history of the Tumalo Project, but the path of groundwater leaving the reservoir floor has never been confidently assessed. The geology and history of Tumalo Reservoir present unique circumstances to explore its potential as a groundwater recharge site. The hydrogeology of the Deschutes Basin as a whole has been extensively studied (e.g. O’Connor, Gannett, Lite). However, I propose that these works were done at a scale that overlooks the refined detail of flow in the Tumalo Reservoir area, the specifics of which make it particularly suitable as a groundwater recharge site. The need for long term water security, coupled with a history of proactive water management planning in the basin, create an exciting opportunity to enhance understanding of the role of groundwater resources in the Upper Deschutes Basin and the extent to which their sustainable use is possible. The feasibility study for groundwater recharge at the Tumalo site determines the likely path of groundwater out of the reservoir, the availability of surface water for recharge, and incorporates analysis of local groundwater wells. A hydrogeologic assessment is used to determine the most appropriate approach for development of the site: direct aquifer recharge or aquifer storage and recovery. The ecological and economic impacts of the implementation of a groundwater recharge facility are examined. Finally, the Tumalo site is compared to the Anchor Dam site in Wyoming, another “failed” reservoir site, to help direct a model for repurposing similar geological sites into regional assets for long-term water management planning.

The Development of Managed Aquifer Recharge in Arizona

Mario R. Lluria
The growth in the use and application of managed aquifer recharge (MAR) in Arizona is an excellent example of progressive development of this technology for the improvement of the management of the limited water resources of a semi-arid region. It can be used as a guide for areas which are evaluating appropiate methodologies to improve the administration of their water supply and demand. In Arizona this development was realized in four phases. Phase 1 (1960s-1980s): EXPERIMENTAL STUDIES: Consisted of academic and institutional research and small scale testing at the University of Arizona and the U.S. Water Conservation Laboratory using both direct surface and well recharge. Phase 2 (1980s-1994): DEMONSTRATION PROJECTS: The need to store excess Colorado River (CAP) water when the Central Arizona Project Aqueduct was completed to Phoenix prompted a Salt River Valley recharge feasibility study (AMWUA) with several pilot tests. Concurrently some were also carried out in Tucson. Phase 3 (1994-2009): DEVELOPMENT OF LARGE CAPACITY WATER-SPREADING FACILITIES: The completion of the Granite Reef Underground Storage Project (GRUSP) with a permit capacity of 200,000 acre-feet/year started this phase and was followed by seven others each with a capacity of more than 50,000 acre-feet/year. Phase 4 (2009-.....): DESIGN, CONSTRUCTION AND OPERATION OF SMALL TO INTERMEDIATE CAPACITY MAR FACILITIES: In this phase projects with storage capacities of less than 20,000 acre-feet/year have and are being developed. They are predominantly for the storage of reclaimed water and are mostly owned and operated by municipalities. In the Phoenix area many of these facilities use vadose zone recharge well (VZRW) which were developed for use at the City of Scottsdale Water Campus facility. Aquifer replenishment and WQ improvement have resulted from this MAR program.

Mining Hydrology

Rory Cowie

Column Testing and 1D Reactive Transport Modeling to Evaluate Uranium Plume Persistence Processes

Raymond Johnson, Ph.D.
At many U.S. Department of Energy Office of Legacy Management sites, natural flushing was selected as a remedial option for groundwater uranium plumes. However, current data indicate that natural flushing is not occurring as quickly as expected and solid-phase and aqueous uranium concentrations are persistent. At the Grand Junction, Colorado office site, column testing was completed on core collected below an area where uranium mill tailings have been removed. The total uranium concentration in this core was 13.2 mg/kg and the column was flushed with laboratory-created water with no uranium and chemistry similar to the nearby Gunnison River. The core was flushed for a total of 91 pore volumes producing a maximum effluent uranium concentration of 6,110 µg/L at 2.1 pore volumes and a minimum uranium concentration of 36.2 µg/L at the final pore volume. These results indicate complex geochemical reactions at small pore volumes and a long tailing affect at greater pore volumes. Stop flow data indicate the occurrence of non-equilibrium processes that create uranium concentration rebound. These data confirm the potential for plume persistence, which is occurring at the field scale. 1D reactive transport modeling was completed using PHREEQC (geochemical model) and calibrated to the column test data manually and using PEST (inverse modeling calibration routine). Processes of sorption, dual porosity with diffusion, mineral dissolution, dispersion, and cation exchange were evaluated separately and in combination. The calibration results indicate that sorption and dual porosity are major processes in explaining the column test data. These processes are also supported by fission track photographs that show solid-phase uranium residing in less mobile pore spaces. These procedures provide valuable information on plume persistence and secondary source processes that may be used to better inform and evaluate remedial strategies, including natural flushing.

Establishing Water-Management Strategy for Slope Stability at Debswana Mines, Botswana

Robert Sterrett
Abstract

The Jwaneng and Orapa Mines of Debswana Diamond Company have reached depths of approximately 300 metres (m), and resource evaluations indicate that the pits will extend to depths of approximately 900 to 1,000 m. These depths will be achieved in approximately 35 years, requiring aggressive planning for how water will be managed to optimize pit slopes. Groundwater, surface water, and pore-pressure controls are paramount if stable slopes and safe mining are to be achieved. In the case of both mines, geologic units that constitute the pit slopes are generally of low permeability, dictating that dewatering/depressurisation systems must be implemented expeditiously.

Numerical groundwater flow modelling for both mines demonstrated that pit perimeter dewatering boreholes will be essentially ineffective in achieving depressurisation goals (that are established by stability analyses). Low-permeability geologic materials prevent effective propagation of low pressures within the dewatering borehole. As such, the focus of depressurisation is on in-pit dewatering boreholes along with sub-horizontal drains. Additionally, emphasis is also placed on preventing enhanced recharge from reaching the perimeters of the mines. Natural recharge from precipitation at the mines is low; however, artificial recharge (for example, from leaking pipes at the processing plants, leakage from tailings and slimes storage facilities, and surface-water runoff from nearby waste rock piles) is high and requires engineering intervention measures in order to maintain slope stability as pit depths increase.

Management concepts for addressing depressurisation include under-drainage utilizing tunnels and drains, eliminating enhanced recharge and future disposal areas located farther from planned pit expansions. In addition, surface-water control systems to intercept and direct precipitation runoff away from the pits are an integral part of effective pit groundwater controls.

The depressurisation and water-management techniques listed above require close cooperation and integration between hydrogeologists, geotechnical engineers, mine planners, and, lastly, mine pit operations personnel.

 

Water Quality Treatment Considerations for Non-Hazardous Disposal Wells Injecting Under Pressure

Chad Milligan, PG
Diminishing capacity of non-hazardous disposal wells injecting under pressure may be related to the water quality and treatment of injectate fluid.  For one coal mine in southern Illinois, native groundwater infiltrating the mine is treated using five main components: coagulation and sedimentation, green sand filtration, reverse osmosis, chemical injection of biocide and anti-scalant, and disposal.  The injection well primarily functions to dispose the concentrate generated from the reverse osmosis treatment system.

The treatment and disposal of native groundwater infiltrating the mine was analyzed using a holistic approach, including an evaluation of the water quality by assessing the chemical and physical characteristics of water, water quantities, water treatment system, geochemistry, and applicable disposal well characteristics.  The analysis identified specific minerals that may be precipitating from the concentrate and causing scaling issues within the disposal well, the specific location within the disposal well the scale could be forming, and recommendations to address the scaling issue both through a well stimulation plan and adjustments to the groundwater treatment system design and operation. 

Understanding how scale forms can help formulate a plan for treating the well.  Temperature and pressure fluctuations can have an impact on solubility coefficients, and can also cause local fluctuations in the equilibrium ion concentration in the solution.  Once the seed crystals start growing, the heterogeneous nucleation process may start at surface defects such as joints, seams, or areas with surface roughness.  A high degree of turbulence can also start the process of scale deposition, such as restrictions in the well. This presentation will focus on why and where scale forms in a groundwater treatment and disposal system and how to prevent it, which will assist to avoid costly workovers and inefficiencies in chemical dosing.

Mining Hydrology

Seth Kellogg, PG

Adit Dewatering at a Proposed Gold Mine: Numerical Analysis of a Large-Scale Long-Term Pumping Test

Dawn Paszkowski, M.Sc.
The high-grade gold Brucejack Project, a proposed underground mine located in northwestern British Columbia, Canada is in the process of being evaluated and developed. Surface topography has a pervasive influence on the groundwater flow system at the mountainous, remote site, which is bounded by temperate glaciers. The complex hydrostratigraphy comprises thin, discontinuous unconsolidated deposits underlain by fractured and faulted metamorphic and volcanic bedrock; coupled with the subarctic climate and abundant precipitation, this leads to considerable seasonal variations in groundwater elevations. Five kilometers of historical underground workings were expanded and dewatered over a 2-3 year period. The resulting field observations provided a dataset not typically available at such an early stage of project development – essentially a large-scale, long-term, variable-rate pumping test.

Groundwater monitoring and flow modeling were completed in support of regulatory approvals and engineering design. The numerical model was developed using MODFLOW-Surfact and was calibrated in stages to available data, including seasonal hydraulic heads, vertical hydraulic head gradients, streamflow and winter low-flow estimates, and volumetric dewatering flowrates. Two distinct approaches were used to represent the underground workings in the model, an active approach using a fracture well and a passive approach using drain boundaries, which helped constrain hydraulic property estimates. Detailed calibration to observed flowrate and hydraulic head response data suggested that the bulk hydrogeological properties of this complex system were well characterized and suitable for further analyses.

The calibrated groundwater flow model was subsequently used to estimate groundwater flow rates to the proposed underground mine and surface water receptors, predict drawdown throughout operations, and simulate recovery of the groundwater system in the closure period for base case and sensitivity scenarios.

Characterizing Lithium Enriched Brines As Mineral Resources and Reserves

Daniel S. Weber, PG
Unlike traditional mineral resources that are solid deposits, brine mineral resources are fluid deposits of variable density and mobility.  As an example, lithium enriched brines are hosted in porous- and fractured-rock aquifers, typically within closed hydrologic basins (salars).  Compared to hard rock deposits, the variable density and mobility of these brine deposits present challenges with respect to exploration, characterization, and quantification. The conceptualization and exploration of brine mineral resources, the mining plan, and definition of the mineral reserve for each deposit require not only an understanding of the spatial and temporal variability of brine densities and concentrations, but also the variability of the flow characteristics in the aquifer where the brine is stored.

As outlined by standards and guidelines for quantifying mineral resources and reserves, key variables such as brine volume and grade, aquifer geometry, hydrogeologic unit, effective porosity, specific yield, flow rate, and recoverability are used in order to meet the definition of reasonable prospects of economic extraction and to define the mineral resource.  Conversion of status from a mineral resource to a mineral reserve requires modifying factors ranging from mining methods, to processing strategies, to environmental, social, and permitting aspects of the project.  

Production wells in deeper deposits, or extraction trenches for shallower systems, are generally the mining methods for extraction of brine resources.  Hydrogeologic methods are thus critical to evaluating what portion of a defined mineral resource is economically extractable and can in turn be defined as a mineral reserve.  Consistent with industry guidelines, we use the technical reporting terms “Drainable” and “Extractable” as factors for evaluating and advancing project status from mineral resource to mineral reserve. These hydrogeologic modifying factors are in part supported using exploration results, aquifer testing, conceptual modeling, and hydrodynamic numerical modeling methods simulating wellfield or trench extraction for mining the lithium-enriched brine.

Geologic Feasibility of Class I Injection Wells in the Deep Portions of the Illinois Basin

Stephanie Hill
The Illinois Basin has experienced a resurgence of underground long wall coal mining operations with the migration of Appalachia-based mining companies over the last decade. This type of mining is conducted under hydraulic roof supports that advance as the coal seam is cut. As the supports advance, the roof collapses behind the cutting head, causing fractures to propagate through water-bearing sandstone formations and resulting in large volumes of fluid infiltrating into the underground workings. Up to 2 million gallons per day have been produced in the southern Illinois mines. The native groundwater contains naturally-occurring elevated chlorides that exceed surface water effluent limitations and are not permitted to discharge to Illinois surface waters. However, the fluid is permitted to be disposed of in Class I non-hazardous wells.

Because there is sparsely documented information available from deep boreholes in the southern part of the state, information from central and northern Illinois was extrapolated for purposes of evaluating the geologic suitability of selected injection intervals for fluid disposal in the deepest portions of the basin. Exploratory boreholes were drilled for two underground coal operations into or near the Precambrian basement with total depths ranging 12,000-13,000 feet. The wells were completed as partially perforated cased/open hole through the injection interval. Cores taken during initial drilling of the boreholes supported published data that one formation displayed vugs that appeared to be interconnected, but laboratory tests revealed an over-consolidated, low porosity and permeability formation lacking interconnectivity of voids. Furthermore, the most suitable formation is thin or absent in the deeper Basin. This presentation will explore the successes and lessons learned from completion and testing of these deep injection wells and examine future drilling and completion practices within the deeper portion of the Illinois Basin.

Poster Session

Aspect Controls on Rock Weathering and Permeability within the Boulder Creek Critical Zone Observatory

Aaron Bandler
We investigate the controls of slope aspect on rock weathering and permeability within the Boulder Creek Critical Zone Observatory by studying the orientation and density of subsurface fracturing. Based on a series of seismic refraction surveys, we compare the seismic anisotropy of the subsurface soil, saprolite (highly weathered, porous rock), and bedrock with the distribution of fractures observed in 7 borehole logs. In rocky mountainous terrain, weathering typically occurs fastest along rock fractures, which we examine on north- and south-facing slopes via the relationship between fracture orientation and seismic velocity. The south-facing slope demonstrates pronounced seismic anisotropy 2-9m below ground surface, with p-wave velocities of up to 2,000 m/s in the E-W direction, and approximately 1,000 m/s in the N-S direction. By contrast, the north-facing aspect demonstrates slower p-wave velocities and less significant anisotropy in this zone, with velocities ranging from approximately 800-1,500 m/s 2-9m below ground surface. We identify this zone as saprolite and observe its upper and lower boundaries to be consistent on both slopes. In the uppermost 2m of both slopes (soil), p-wave velocities are approximately 500 m/s in all measured directions. Below 9m (bedrock), p-wave velocities are approximately 3,500-4,500 m/s in all measured directions. Borehole logs show conjugate sets of fractures on both slopes striking in a general E-W direction, consistent with the direction of anisotropy observed in the south-facing saprolite. Based on current weathering models, we interpret the slower and more isotropic velocities of the north-facing saprolite to be the result of more intense weathering triggered by a colder average surface temperature and more intense spring runoff than the south-facing slope. Assuming that both slopes experience similar tectonic stress, we interpret the differences in the saprolite velocities of the two slopes as evidence that slope aspect controls rock weathering and permeability.

Assessment of Surface and Ground Water Quality in Ganaja, Lokoja, North-Central, Nigeria

Ngozi-Chika Chiazor
The increasing rate in population, poor sanitation habits, flooding and lack of enforcement of environmental Sanitation laws in the study area have contributed immensely to the pollution of water sources. Thus, water samples were obtained from river Niger, hand-dug wells and a bore-hole in Ganaja, Lokoja, north-central, Nigeria for water quality analyses. The hydro-geochemical results showed that the pH values range from 6.70-7.70 indicating alkaline water type. The water hardness of the hand dug wells rage from 7.46 - 241.09 with an average value of 110.30 indicating soft to moderately hard water. The hardness value of sample (HW-S8 = 53mg/l, HW-S9 = 241.09 mg/l, HW-SW10 = 152.87mg/l, HW-S11 = 207.78mg/l, HW-S12 = 155.67, HW-S14 =152.03mg/l, HW-S15 = 150.11mg/l) and the TDS for sample (BH-S1) is 525mg/l, the concentrations of K in HW-SW10 = 13mg/l and Ca in HW-S11= 79.89mg/l. These are all above the WHO admissive limit. The value of the physico-chemical parameters such as the ToC, Ec, BOD, COD, HCO3, CO3, SO4 Cl, NO3 Na, Ca Mg, and the heavy metals including Pb, Cd, Cu, Fe, Mn, Ni and Zn as well as the concentration of TDS, Ca and K  in all other waters samples are within the allowable limits. TDS is linked to taste, hardness, corrosion properties and tendency for incrustation by water. Negative association between water hardness and cardiovascular disease have been observe. Hard water can cause aesthetic problems. An increase K in the blood is known as hyperkalemia appears as reduced renal functions, abnormal breakdown of protein and severe infections. It is advisable that the water be treated against hardness, TDS, Ca and K before consumption or other domestic use..

Behavior of a Fault Arose By a Water Level Variation and Its Poroelastic Understanding - a Case of a Fault Near Tries -

Hiroshi Ishii, Ph.D.
Behavior of a fault arose by a water level variation and its poroelastic understanding   - a case of a fault near TRIES -

ISHII Hiroshi and Yasuhiro ASAI,

Tono Research Institute of Earthquake Science (TRIES), Association for the Development of Earthquake Prediction (ADEP).

Tono Research Institute of Earthquake Science (TRIES) has developed a multi-component borehole instruments for continuous observation.  The instrument is equipped with stress meters, strain meters, seismometers, tilt meters, magnetometers, and a thermometer, and we can choose the contents of the instrument as we like.  At the present time about 15 borehole stations are in operation. The depth of the deepest borehole is 1030 m. There is a fault near our institute. We have investigated a relationship between a variation of underground water and a behavior of the fault by using geophysical data obtained from borehole observations.  

Near our observation stations deep boreholes with diameters of 4m and 6.5m are under construction. And depth is about 500m at the present time. During the construction spring water sometimes happens and we analyzed the data caused by this. We also made experiments of water pumping out for a borehole near the stations and analyzed the data caused by this.

  The main results obtained are as follows: 1: water level of TGR350 borehole station with 350m depth decreases by the pumping water and the spring water. Data of the strain meters installed at 350m depth indicate right lateral movements of the fault near TRIES. 2: data of the strain meters installed at 350m depth indicate left lateral movements of the fault in case of recovery of water level.  3: strain meters installed at shallower depth (165m) and extensometers installed in sedimentary layer do not indicate such fault movements.  4: we have considered a mechanism explaining the phenomena by using poroelastic understanding.

Combining Geochemisty/Geophysics to Pinpoint Sources of Salinity in the Rio Grande and the Relationship to Faults

Matthew Hiebing
Fresh water resources are scarce in American Southwest, especially in the arid regions of El Paso, TX.  The Rio Grande River and the Mesilla Bolson aquifer are both major sources of freshwater for the city of El Paso and its croplands along the river. Maintaining a steady supply of freshwater is critical in sustaining the increasing demands of irrigation and population growth in the area.

For decades scientists have been trying to understand why there is an great increase in salt content from ~40mg/L at the headwaters of the Rio Grande in Colorado to ~1500 mg/L in El Paso, TX. The increased salinity has limited its use as city drinking water and agricultural irrigation water. The saline water causes problems such as increased soil salinity and reduction of crop productivity. This project focuses on pinpointing sources of salinity in the Rio Grande and its relationships to the fault systems within the Mesilla Bolson using a combination of water geochemistry and geophysical data. 

Previous studies suggest multi-source contribution of salt to the overall salinity of the Rio Grande.  This study has attempted to assess two main sources: 1) natural upwelling of saline groundwater through subsurface faults; and 2) return flows from the agricultural fields after irrigation with Rio Grande water and groundwater.  Previous gravity studies have exposed a complex fault network throughout the Mesilla Bolson.  This study has combined these datasets with new geophysical investigations to infer groundwater flow paths along the fault systems. Modeling the flow system of the Mesilla Bolson and its relationship to the Rio Grande can expose a potential salt influx from the faults of the Mesilla Bolson. Furthermore, the geochemistry of groundwater samples will be used to distinguish salinity sources from the natural groundwater upwelling and the agricultural return flows to the Rio Grande.

Designing a Permeable Reactive Barrier for Groundwater Remediation using Water Treatment Residuals

Christopher Walkons
Permeable reactive barriers (PRBs) present an attractive option for sustainable groundwater remediation. Not only is the barrier a passive system, but a PRB can often be constructed using reused materials. In this project we are designing a pilot-scale PRB for the removal of copper from groundwater. The reactive material for the barrier is the residual of coagulants used in drinking water treatment operations. The physical and chemical properties of this water treatment residual (WTR) have been studied to optimize PRB design. Batch reactor tests have shown that equilibrium sorption of copper to the WTR is best described with a Langmuir type isotherm and that the sorption capacity of the WTRs could allow a PRB lifetime on the order of decades. Kinetic batch and column tests have also been conducted to understand the significance of chemical and physical mass transfer limitations. A leaching test indicated that the WTR materials will not release contaminants into the environment. Constant head permeameter tests were performed with various mixtures of the WTR and an inert support material (pea gravel) to determine the ideal mix for matching the test site’s hydraulic conductivity. Additional work has been conducted at the site to determine aquifer depth, groundwater flow velocity, and contaminant concentration for designing the optimal dimensions and placement of the PRB.

Geophysical Evaluation of Hyporheic Flow Beneath an In-Stream Structure in Fine Sediments

Jenna Fontaine
The hyporheic zone is a three-dimensional region where surface water and groundwater mix. In-stream structures can induce hyporheic flow due to a change in hydraulic gradient. Little research has been conducted to evaluate the hyporheic zone in fine sediments. This study uses electrical resistivity imaging to determine the presence of the hyporheic zone beneath a J-hook in the restored portion of a fine-grain losing stream in Oklahoma. A saline tracer was applied to track fluid movement with ERI over time based on tracer’s electrically conductive properties. Cross-sectional and longitudinal background images act as controls, while longitudinal datasets were collected during the inflow of tracer. Hyporheic flow was observed as deep as two meters below the J-hook in support of the original hypothesis, while some tracer may have propagated several meters deep as a result of fluid density differences.

Ranking of the Remedial Priority of Contaminated Sites Using a Fuzzy Rule Based System

Aysegul Aksoy
Ranking of contaminated sites for remedial priority is a concern especially for orphan sites. Ranking may be required to allocate limited resources efficiently given temporal and financial constraints. For this purpose, high quality data may be required for comparison of the severity of pollution at different sites. Yet, in most cases, input parameters relevant to contaminant fate, transport, and exposure are vague or not precise. In this study, an alternative remedial priority ranking system is developed which considers the vagueness in parameters relevant to contaminant fate, transport, and exposure pathways in ranking of the remedial priority of contaminated sites. The system is based on fuzzy theory. Potential human health risks due to contamination are assessed using sufficiently comprehensive and readily available parameters in describing the fate and transport of contaminants in air, soil and groundwater. The system was incorporated into software for ease in application. Rankings were employed for different contamination cases of varying levels of severity. Results indicated success in distinguishing between higher and lower risk cases.  

Smart Energy and Water Meter (SEWM): An Innovative Approach Towards Groundwater Monitoring and Management

Hassan Kashi
Water scarcity, threat of water crisis, and drought have been identified as the immediate consequences of various factors, which influence the deterioration of agricultural land, water resources, environment and economy. The main factors include descent precipitation, relying on traditional irrigation methods, inefficient monitoring and controlling systems in agriculture section. Furthermore, over-pumping is the main cause for groundwater shortage and sharp decrease of water tables in arid and semi-arid regions around the World.
While there are different methods to measure, control and manage groundwater resources in the World, however most of these methods are facing common issues of typical meters such as sensitivity and vulnerability against suspended particles, air bubbles, pipes’ slope, existence of tap, bend and connections. As such, in this paper, RSA Electronics Co. presents a novel solution, which is an effective management system for monitoring and management of groundwater resources by eliminating these common issues.The core section of this solution is a smart meter, which is called Smart Energy and Water Meter (SEWM). This innovative solution is the result of continues research and development activities, patented in US in the field of measuring electricity, and water includes the following sections:
  • The meter (SEWM) which is an active/reactive multi-tariff device, measures and records consumed-energy and relevant parameters required by the energy authorities.
  • The SEWM also is capable of measuring and storing the amount of water withdrawal, water flow and other quantitative parameters. The meter indicates water credit, validity of start and expiry date; also, it is capable of reacting based on the client’s demand if user exceeds allowed credit water or credit time is over.
  • The collected details of water wells are transferred to the control center via telecommunication infrastructure ; data processing and reporting is performed by Meter Data Management software.

Spatiotemporal Assessment of Groundwater Resources in the South Platte Basin, Colorado

Christopher J. Ruybal
The South Platte Basin is one of the fastest growing basins in Colorado and faces strong competition for water resources. Water sustainability challenges in an over-appropriated system will need to be addressed to meet future water demands. Balancing the conjunctive use of surface water and groundwater from the South Platte alluvial aquifer and the Denver Basin aquifer system is critical for meeting future demands. Over the past decade, energy development in the basin has added to the competition for water resources, highlighting the need to advance our understanding of the availability and sustainability of groundwater resources. Current work includes evaluating groundwater storage changes and recharge regimes throughout the South Platte Basin under competing uses, e.g. agriculture, oil and gas, urban, recreational, and environmental. Groundwater data is used to evaluate spatiotemporal variability in groundwater storage and identify areas of high water stress. Spatiotemporal data will also be utilized to develop a high resolution groundwater model of the region and assess recharge regimes. Results will ultimately help stakeholders in the South Platte Basin better understand groundwater resource challenges and contribute to Colorado’s strategic future water planning.

Sustaining Water Supply from Groundwater Resources through Nyabarongo River Bank Infiltration, Kigali City Rwanda

Rani Fouad, Dr.
Lack of access to water supply in Rwanda has a significant health impacts, in which imposes a significant burden on women and girls who have to carry water. For instance, more than one in five households in Rwanda is more than an hour away from its water source. In order to improve the sustainability, the government of Rwanda has signed a contract to develop a new sustainable bulk water supply plant in Kigali to serve Kigali city’ potable water requirement. The plant will be located at south bank of the Nyabarongo River in the South Eastern part of Kigali city, and will supply 40,000 m3/d of treated water. As in tropical areas, Nyabarongo River has a significant flow during wet season; however in dry season (July to October) it’s difficult to fulfill the water needs through a direct river intake. In order to secure the continuity water supply, the government aimed to setup a new groundwater well-field to fulfill the required water demands. This paper shows the used technique for design of well-field and quantification of groundwater system recharge through the river bank infiltration which will insure the continuity of water supply during the dry season.

Texas Brazos River Alluvium Aquifer Initiative: Working Together to Monitor and Manage Groundwater

Joe C. Yelderman Jr., PhD, PG
The Brazos River Alluvium Initiative (BRAI) consists of Baylor University and Southern Trinity Groundwater Conservation District (STGCD) working with private landowners to gather data to manage the water-bearing sediments of the Brazos River in McLennan County, Texas. Without the above participants, the county-wide understanding of the Brazos River alluvium aquifer (BRAA) would be difficult and fragmented. The BRAA has mainly served as irrigation water, however, with water demand in McLennan County increasing, alternate sources of water are being investigated. The goal of this work is to provide decision makers scientifically based data to manage the BRAA.  To date, there has been no consistently identified network of monitor wells to manage the BRAA as has been done with other aquifers in the county. Regional studies and monitoring in the BRAA have been conducted, but not using a network of continuous and monthly data logged water level measurements. This proposed network of wells will be used by the STGCD in combination with hydrogeologic interpretations by Baylor to understand and manage available alluvium water.  The STGCD has the legislative directive to conserve, preserve, protect, recharge and prevent the waste of groundwater as found in the Texas Water Code. The goals of the university are to conduct research and prepare students to interpret the BRAA interbedded and complex geometry of upward fining-sediments ranging in size from clay to gravel in the BRAA. Once the network is in place, additional and long term areas of BRAA research include: recharge rates from rainfall and river stages, sustainable yields from alluvium wells, and contamination impact assessment.

Poster Session

Applying IDEXX SNAP Kits to Testing for Antibiotic Residues in Water

Melissa Lenczewski, Ph.D.
Antibiotics are an emerging environmental contaminant. Their presence is increasing in the environment due to excessive distribution of antibiotics to livestock and humans. The danger lies within the increased potential of antibiotic resistant bacteria. Antibiotics enter water through human, industrial, and animal waste resulting from treatment plants, hospitals, and confined animal feeding operations. CAFOs house a disproportionate number of animals in tight quarters and administer excessive amounts of antibiotics to prevent disease and promote growth resulting in excreted antibiotics through urine and feces. The manure produced harbors antibiotics that are dumped or leached into waterways. Current test methods take one week, require intense chemistry, and cost around $500 for a 1L sample. IDEXX SNAP kits are potentially a cheap, convenient, and quick on site alternative. These test kits are currently used to monitor the presence of antibiotics in milk. The purpose of this research is to determine if IDEXX SNAP kits have a viable application towards testing water.

Four variations of IDEXX SNAP test kits including Tetracycline, New Beta-Lactam, Gentamicin, and Sulfamethazine were used to test for the presence of 8 antibiotics within water. All samples were tested in triplicate. Individual solutions of 1% milk were spiked with each antibiotic and tested in the corresponding SNAP kit at 100ppb to serve as controls. Distilled water was tested in all SNAP kits as a second control. A stock solution of 1000ppb was created for each antibiotic, diluted further in distilled water, and tested at concentrations of 1ppb-100ppb. Each 100ppb spiked distilled water sample was also tested with the three non-corresponding SNAP kits to determine cross reactivity

Preliminary results indicate that tetracycline can be detected in water between the concentrations of 100ppb and 10ppb using the tetracycline IDEXX SNAP test. Below 10ppb tetracycline is not always detectable. Previous research reported positive tetracycline results in surface and ground water. Results from the remaining antibiotics are to be determined.  IDEXX SNAP kits are potential quick and cost effective tools to detect antibiotics in the environment.

Assessment of Scaling Potential Associated with Using Desalination Concentrate As Hydraulic Fracturing Fluid

Nima Ghahremani, Doctoral Student
The main purpose of this study is to evaluate the feasibility of using concentrate streams from brackish groundwater desalination plants located within the Eagle Ford Shale region as hydraulic fracturing fluid. As part of this study, a time-series water quality analysis has been carried out on concentrate samples from the City of Kenedy, Texas brackish groundwater desalination plant. The results have shown low concentrations of total dissolved solids (TDS) and problematic multivalent ions over a year of monitoring. In addition, geochemical modeling analyses are being performed to assess the down-hole potential associated with using the concentrate water as hydraulic fracturing fluid.  This geochemical modeling is being performed using the PHREEQC geochemical software package and using the results of the concentrate chemical characterization studies along with the in-situ temperature and pressure. The down-hole scaling potential associated with different blend ratios of flowback water and desalination concentrate are also being simulated in the model.  The results of this study will provide a framework for identifying opportunities and obstacles for using brackish groundwater desalination concentrate for hydraulic fracturing operations. Lessons learned can be applied to other brackish water sources, including cooling tower blowdown from refineries and power stations. The concentrate characterization and geochemical modeling studies will also complement ongoing flowback water treatment research.

Climate Change and Remediation: Droughts Inhibit Site Characterization and Monitoring of Contaminated Sites

Andrew Nunnery, PhD, PG
Monitoring of groundwater at contaminated sites has become more difficult in drought-stricken areas due to the fact that drought conditions may decrease groundwater elevation causing monitoring wells to go dry, and possibly result in changes in groundwater chemistry and the volume or presence of NAPL.  These conditions can impair hydrologists’ abilities to properly characterize sites and lead to unrealistic understanding of subsurface conditions that may translate into poor decision making and unexpected costs to clients. The drought experienced in the Southwest United States starting in 2010 is part of a hydraulic cycle related to El Niño Southern Oscillation in the Pacific Ocean, and is similar to conditions observed during previous dry periods. However, the National Climate Assessment indicates that projected changes in temperature and precipitation for this region will exacerbate the effects of these shorter term climate cycles, further inhibiting our ability to monitor contamination in the subsurface and increasing uncertainty when planning remediation strategies.

This study examines the effects of the recent drought on groundwater monitoring at four sites in Texas and California: two hydrocarbon contaminated sites in south Texas, one hydrocarbon contaminated site in southern California, and one hazardous waste disposal facility in southern California.  At the two Texas sites, water level decreases resulted in an approximate loss of up to 30% of the monitoring well network. Conditions were more pronounced at the southern California sites, with water level decreases resulting in up to 55% loss of the monitoring well network.  At all four of these sites, the decrease in the water table caused the loss of important spatial and temporal site characterization data. The results of this study highlight the need to consider how short-term and long-term climate change may affect efforts to characterize and remediate contaminated groundwater.

Conditioning geostatistical simulations of a bedrock fluvial aquifer using single well pumping tests

Amir Niazi
Geostatistical simulation is a powerful tool to explore the uncertainty associated with heterogeneity in groundwater and reservoir studies. Nonetheless, conditioning simulations merely with lithological information does not utilize all of the available information and so some workers additionally condition simulations with flow data.

In this study, we introduce an approach to condition geostatistical simulations of the Paskapoo Formation, which is a paleo-fluvial system consisting of sandstone channels embedded in mudstone. The conditioning data consist of two-hour single well pumping tests extracted from the public water well database in Alberta, Canada.

In this approach, lithologic models of an entire watershed are simulated and conditioned with hard lithological data using transition probability geostatistics (TPROGS).  Then, a segment of the simulation around a pumping well was used to populate a flow model (FEFLOW) with either sand or mudstone. The values of the hydraulic conductivity and specific storage of sand and mudstone were then adjusted to minimize the difference between simulated and actual pumping test data using the parameter estimation program PEST. If the simulated data do not adequately match the measured data, the lithologic model is updated by locally deforming the lithology distribution using the probability perturbation method (PPM) and the model parameters are again updated with PEST. This procedure is repeated until the simulated and measured data agree within a pre-determined tolerance. The procedure is repeated for each pumping well that has pumping test data.

The method constrains the lithological simulations and provides estimates of hydraulic conductivity and specific storage that are consistent with the pumping test data.  Eventually, the simulations will be combined in watershed scale groundwater models

Groundwater Flooding Solutions Through Collaborative Learning Framework

Joseph Kemper
Since the 1970s, residents of Falls City, a small town in the foothills of Oregon’s Coast Range, have excavated a network of drainage ditches to divert floodwaters during heavy winter storms.  These diversions lack a cohesive hydrologic strategy.  Landowners often independently drain their land, sending water to downstream neighbors, creating considerable conflict in the small community.  OSU researchers have introduced a collaborative learning framework to help reduce conflict and simultaneously gather local expertise to work towards a solution.  Weather, stream and geologic records are combined with valuable local knowledge to provide a preliminary picture of flooding dynamics.  Observations suggest that groundwater drives the observed flooding.  A geotechnical survey is conducted to assess the surface and subsurface hydrology of the South Falls City Flooding Zone.  A monitoring well is installed to measure alluvium depth to bedrock and investigate subsurface processes in south Falls City.  Seasonal water table fluctuations and aquifer tests are used to characterize the hydraulic properties of the aquifer.  Results show that groundwater flooding plays an active role in the stormwater flooding.  Minor surface diversions will not likely eliminate flooding during high precipitation events.  LiDAR elevation data and HYDRUS modeling software are used to simulate several engineered dewatering measures to mitigate flooding.  These measures are combined with community sourced surface diversion to create a comprehensive flood mitigation plan for South Falls City.  The South Falls City Flooding Zone is yet another identified case of groundwater flooding and will worsen if global climate shifts increase storm intensities in the Pacific Northwest.  Similar community collaboration, however, could be useful for rural communities that need to adapt to harsh winter flooding.

Modeling Coseismic Groundwater Level Change with the Constraint of Gravity Data

Ryo Honda
The absolute gravity measurement by FG-5 gravimeter has been operated in three stations in and around the Tono Research Institute of Earthquake Science (TRIES) since 2003. During this period, two types of ground water level change was observed. One is the water level decrease more than 80 m in 12 years, which along the excavation of the 500 m deep shafts of the Mizunami Underground Research Laboratory (MIU). The other is the coseismic water level change. Generally, the gravity value increases if the groundwater level increases, and vice versa. Nevertheless, the gravity values in 3 stations show no decrease along with water level decrease in 12 years. The obvious coseismic gravity change was observed only in two cases. One is in the 2004 off Kii Peninsula Earthquake (Tanaka et al., 2006, G3), and the other is in the 2011 off the Pacific coast of Tohoku Earthquake. The distances of the gravity stations are within 2 km. The coseismic gravity decrease for the 2011 Tohoku earthquake were about 10 micro gals in all these stations. This suggest that the mass equivalently moved away from these three stations. Based on former researches of hydraulic geology which clarified the permeability structure, we suggest a model of the coseismic groundwater flow, which is explicable for both gravity and groundwater level data. The basic concept of our model is that “the water flows downward by earth’s gravity”.

Quantifying CO2 Degassing and d13C Using a Floating Chamber in a Gaining Headwater Stream

Brock Norwood
Scientists still debate the sources and sinks of carbon on the earth’s surface. Headwater streams, a carbon source often overlooked in the carbon balance equation, cover more than 50% of the total stream length in the conterminous U.S. Shallow groundwater discharge is the main contributor to the baseflow and CO2 concentrations in headwater streams. Groundwater datasets at the Konza Prairie Long-Term Ecological Research Site (Konza) demonstrate an increase in groundwater pCO2 by approximately 29% from 1990 to 2009. This continuous increase suggests that headwater streams, recharged by shallow groundwater, could be a significant carbon source.

We used a floating chamber to measure CO2 degassing rates in a headwater stream reach at Konza. Temperature contrasts, seen with an infrared camera, between discharging groundwater and the stream, located groundwater seeps. We found that groundwater discharge occurs primarily along the stream bank or in fractured bedrock on the stream bottom. At each seep, we collected water samples for major-ion chemistry, δ13C of CO2, and δ13C of dissolved inorganic carbon (DIC). Because the limestone aquifers crop out in the stream, we also collected groundwater samples from nearby wells completed in those limestones.

We compare stream water and groundwater to assess the changes that occur during groundwater discharge to a headwater stream.  Preliminary results show stream water degassing at rates between 1.82 and 58.4 g C m2-day1-. The CO2 fluxes and pCO2 decreased with distance from the seeps (~2 meters). Decreases in fluxes and pCO2 were accompanied by heavier carbon isotopic ratios, with δ13C—CO2 increasing downstream of groundwater seeps. Furthermore, groundwater and stream water chemistry were similar for major anions, major cations, and alkalinity. This study provides additional understanding of groundwater and surface water interactions and evidence of a significant contribution to atmospheric carbon from headwater streams in the region.

Quantifying Potential for Spills at Unconventional Gas Well Sites to Impact the South Platte Aquifer

Cynthia Kanno
With the rise in unconventional oil and gas development over the past decade, the public is concerned about how these stimulation, extraction, and production activities may impact groundwater resources. Although there are many possible ways for accidental leakage to occur and different fluids that could be released, the most probable contamination pathway is through surface spills of produced and hydraulic fracturing fluids. These fluids could potentially infiltrate through the vadose zone, reach the groundwater table, and be transported. The purpose of this study is to conduct fate and transport simulations of surface spills of chemical contaminants, such as biocides, friction reducers, surfactants, and hydrocarbons, typically found in hydraulic fracturing fluid and produced water. Accounting for degradation, sorption processes, co-contaminant interactions, and spill statistics, we seek to understand the hydrologic and site conditions under which a surface spill would pose risk to groundwater quality. This study focuses on the South Platte Alluvial Aquifer, which overlaps a zone of high-density oil and gas development in the greater Denver metro area. We propose a coupled analytical-numerical approach that could be reproduced by environmental consultants. Preliminary results suggest that risk of groundwater pollution, based on predicted concentration at the groundwater table, is low in most areas of the South Platte system for the contaminants investigated. However, substantial risk may exist in certain areas where the groundwater table is shallow. In addition, transport of certain contaminants is influenced by interactions with other constituents in produced or stimulation fluids. By helping to identify locations in the Front Range of Colorado that are at risk for groundwater contamination due to a surface spill, it is our hope that this work will aid in improving best management practices so that decision-makers can be better prepared to address accidental releases in Colorado.

Remarkable Crustal Tilt Variation Caused By Excavation of Underground Gallery

Yasuhiro Asai, Ph.D.
Tono Research Institute of Earthquake Science (TRIES) has been investigating the relationship between the variation of groundwater level and variations of crustal tilt, stress, and strain.

We have developed a Borehole tiltmeter (Ishii et al., 2002) and installed it at the bottom of two boreholes site (STG100 and STG200) in the Mizunami underground Research Laboratory (MIU) in the Tono region, central Japan, as a part of the research. The Tono region is a relatively stable block of Cretaceous Toki granite uncomformable overlain by Tertiary layers (Mizunami sedimentary formations) with a thickness of approximately 100-200m (King et al, 1999, JGR). The STG100 site is located in the Tertiary layers, and the STG200 site in the Toki granite.

As research advances, the following results were obtained: (1) Amount of tilt-down variation at the STG100 site is approximately 1.7×10-5 radian/yr, and variation for the STG200 site is approximately 1.0×10-5 radian/yr. (2) Direction of observed tilt-down variation at both site are almost south-southeast.

In addition to above observation result, groundwater with volume of 700m3 was generally pumping a day in MIU (Kimata et al, 2015, Engineering).We consider that observed tilt-down variations may be caused by the “source” located in neighboring south-southeastern area of MIU.

Simulating the Extent of TCE Contamination in Antrim County, Michigan Using Publicly Available Data

Ashley Miller
Access to data necessary to construct, calibrate, and test groundwater flow models poses a primary challenge in groundwater and contaminant transport modeling. Spatial data appropriate for model input are, however, becoming increasingly available for download through state and federal agencies. Despite the access to publicly available data, most modeling efforts rely on expensive project-focused site investigations, in part because the data are collected with the purpose of creating model input. We explored the value added for site investigation data in constructing a model for simulating the groundwater flow field for a large trichloroethylene (TCE) plume in Antrim County, Michigan. Located in a heterogeneous glacial aquifer system, the plume extends approximately six miles northwest from the industrial source area and is estimated to affect four primary water-bearing zones that supply drinking water to the Village of Mancelona and surrounding area, including individual wells for rural residents. Spatial data downloaded from the Michigan Geographic Data Library, and other online sources, were used as a means to characterize the hydrogeology of the subsurface, formulate inputs for the regional conceptual model and subsequently develop numerical (MODFLOW-2005) groundwater flow models of varying complexities. This modeling approach was successful in simulating the groundwater flow using a the three-layer system by calibrating recharge and hydraulic conductivities that agreed with independent estimates of recharge and aquifer properties. In order to analyze the value added from site characterization data, the model based on publically available data was reformulated using the plume-project site investigation data, which included monitoring well soil-boring logs, monitoring activity records, geophysical seismic surveys, and source site evaluations. The final analysis provides insight to the models’ ability to simulate field data, forecast behaviors of production wells, and serves as the basis for recommendations for plume capture.

Subsidence Following Groundwater Drawdown By Excavating of Deep Shafts in Granite in Mizunami, Japan in 2004-2014

Fumiaki Kimata
Two 500 m deep investigation shafts were excavating in the granite body in Mizunami, central Japanby JAEA (Japan Nuclear Cycle Development Institute) in 2004-2012. Groundwater with volume of 700 m3 was generally pumping a day to prevent the shafts from submerging in 2012 following the excavating. As a result of pumping the groundwater, the ground water level lowered to 60 m in the borehole with the distance of 200 m from the excavating shafts in 2012. Leveling network extending 2 km × 2 km around the shafts was established to detect the vertical deformation around the shafts in 2004, and precise leveling was done every year. An 18 mm ground subsidence was detected in the benchmark close to the shafts for 8 years in 2004-2012, and time series of subsidence at benchmark was consistent with the groundwater drawdown. The groundwater drawdown and ground subsidence were caused by the pumping ground water in excavating shafts.

In 2012, we extended the leveling network to a width of 4 x 5 km around the excavating shafts, and we had precise leveling in 2012, 2013, and 2014 at the network. As results, subsidence of 4mm is detected around the shafts, and subsidence areas are enlarged to the southeast and northwest in 2012-2014.

A depth distribution of granite in the area is estimated from aeromagnetic surveying. As results, Two groundwater veins are suggested in NW to SE and NNE to SSW, which is a good consistent with ground subsidence distribution.

As subsidence is only 2mm/year, we hope to repeat precise leveling for few years, and to make clear the groundwater system around the shafts.

Waste Rock Biogeochemical Environments in a Sub-Arctic Climate Above and below a Leaky Thermal Cover

Jeff Langman
The colonization and weathering of sulfide minerals by Fe- and S-oxidizing bacteria in aerobic waste rock at a sub-Arctic, mine-waste research site is counterbalanced by the extreme climate. Experimental waste rock piles were constructed to examine the mine's closure design of a double layer cover composed of a low sulfide waste rock and low permeability till atop the higher sulfide waste rock. Leachate from these experiments indicated variable pH and SO4 concentrations because of sulfide content and a temperature-moderating influence by the till. The thermal moderation below the till provided a more stable environment for the production of acid, growth of acidophilic Fe- and S-oxidizing bacteria, and enhanced weathering during wet up; however, the production of acid rock drainage was limited after saturation and freezing of the fine-grained matrix. Examination of sulfide weathering in the closure design indicated a strong SO4 signal above the till and less oxidation and no difference in S speciation below the till. Examination of the bacterial communities indicated the prevalence of Pseudomonas, Rhodanobacter, Sideroxydans, and Thiobacillus in the waste rock. Pseudomonas were dominant in the drier and more extreme environment of the freeze-thaw zone above the till, and Thiobacillus were dominant in the wetter/frozen environment below the till. A decreasing trend in Thiobacillus from the exterior to the interior and an opposing trend in Acidithiobacillus suggest more extensive sulfide oxidation and acid generation occurred deeper in the interior of the waste rock prior to onset of frozen conditions. Although the presence of the till layer in the cover may have initially moderated temperature variations and enhanced initial weathering in the underlying waste rock, it also increased water retention and led to a continually frozen waste rock. The heterogeneity of microbial populations and geochemical environments was still apparent in this moderated but frozen environment.

Water Well System Reliability and Reduction in Field Operations Costs

Gary Luce
In oil and gas fracking operations, not actively managing the reliability of your water well supply system can expose your company to significant standby fees from your pressure pumping OFS partner as well as increased last minute truck traffic on the lease roads to the frack pits.

System reliability is affected by well pump-offs driven by mismatch of aquifer supply and the pump/motor size or back pressure from the flow lines size, length or system configuration. Not actively minimizing these pump-offs can increase Capex requirements due to damage from continuous across the line starts. Since many of these wells are remotely located, there is a high operations cost to identify which wells have gone down and to get the correct resources to repair them into the field.

New technology is available to remotely manage these systemic risks associated with a water well supply system. Combining power management equipment with 4th generation SCADA and cloud/server based active management systems produces significant economic benefit from improved water supply reliability and reduced opex and Capex exposures.

Water Rights/Water Law

Implementing SGMA — California's Foray into Groundwater Regulation

Leslie Dumas, P.E., D.WRE
In November of 2014, the California governor signed the Sustainable Groundwater Management Act (SGMA), 100 years after the passing of the Water Commission Act of 1914 which established California’s surface water rights and permitting process. Effective January 1, 2015, SGMA establishes a new structure for sustaining groundwater in California and, for the first time, attempts to manage groundwater use in the state outside of the legal courts. While the goal of SGMA is unmistakable, the Act itself provided a clear timetable for implementation along with a mixed bag of useful tools for sustainable groundwater management and conflicting directions which have the potential to stymie implementation. Now almost one year into the process, state regulators are scrambling to develop guidelines and regulations while water agencies and public entities grapple with the implications of the Act and initiate tentative steps towards meeting key deadlines. In general, SGMA compliance consists of four key steps: (1) designation of basin priorities and identification of basins that are in critical overdraft; (2) determining if groundwater basin or subbasin boundaries require modification and addressing these changes; (3) development of Groundwater Sustainability Agencies (GSAs); and (4) preparation of Groundwater Sustainability Plans (GSPs). Presented herein are summaries of progress made to date relative to complying with SGMA, problems that have arose and solutions suggested, and an assessment of what SGMA implementation will really mean for the state of California as it tries to achieve groundwater sustainability by the year 2040.

Protecting Your Water Supply and Your Bottom Line: Shifting Costs from Ratepayers to Responsible Parties

Richard Head
Water suppliers and water treatment operators face unprecedented financial challenges as they endeavor to comply with increasingly stringent drinking water standards. Despite the fact that much contamination was caused by businesses who released chemicals into the environment as part of their operations, the water supply industry traditionally has been reluctant to use tort litigation to seek to recover treatment costs from those business polluters. One reason is that water suppliers often think that the only prospective defendants are the small local businesses who were the last to touch product whose chemical components eventually entered and harmed the water supply. These small local businesses generally do not have sufficient financial resources or insurance coverage to reimburse the water supplier for the cost of responding to the contamination.

Recent lawsuits by some water suppliers have successfully pursued an innovative legal strategy. These new cases do not focus on the end user who last touched the product but on the manufacturer of the product who introduced it into the stream of commerce. These innovative cases include lawsuits by water suppliers against the refiners of gasoline containing MTBE, the manufacturers of other products including PCE (used by dry cleaners), TCE (used by a variety of industrial users), and DBCP, TCP, and Atrazine (used by farmers). This new legal strategy has resulted in hundreds of millions of dollars being paid to water suppliers by manufacturers of products which contaminated water supplies.

This innovative approach to water contamination litigation has important implications for water suppliers, lawyers, regulators, and environmental consultants. This presentation will discuss the legal theories underlying these landmark cases and the status of lawsuits currently pending in jurisdictions around the country. The presentation will also discuss the legal and political responsibilities facing a water supplier whose water supply has been impacted by man-made pollution.

The Effects of Self-Imposed Economic Incentives on a Groundwater Commons

Kelsey Cody, Master of Science
Many globally important groundwater aquifers are under extreme stress. Withdrawals, predominantly for irrigated agriculture, are outpacing recharge. The situation is exacerbated by increasing human demand for fresh water as well as a changing climate that alters surface water availability. With many users drawing from a shrinking common-pool of water, it is easy to fall prey to a “tragedy of the commons” and extract water at a rate exceeding the social optimum. Some attribute the current crisis to failures of top-down governance to effectually alter water use. Even in arid areas of the world, extraction of scarce groundwater has not been well regulated. Unregulated irrigators often consider only individual pumping costs when determining how much to extract, ignoring the cost they impose on their neighbors and future irrigators. In some jurisdictions governments are starting to respond with increased top-down regulation: spacing requirements; technological standards; pumping quotas; and in some places, complete shutdown of existing wells. Despite the theoretical cost-saving benefits, few regions have imposed economic incentives due to transaction costs and political frictions. Recently, irrigators in San Luis Valley, Colorado in the United States have sought to stave off state regulation and maintain local flexibility by self-imposing a tax on the water they pump. The goal of this paper is to assess the effectiveness of this self-organized policy in altering irrigators’ behavior. We find that the intervention has led to a movement away from water-thirsty crops, relatively more use of efficient irrigation technology, and, most importantly, significantly reduced volumes of water extracted. Our results show that self-governance and economic incentives are viable alternatives to top-down, command-and-control regulation in an era of global water stress.