NGWA Conference - Hydrology and Water Quality in the Southwest : Alphabetical Content Listing
Mining Impacts on Groundwater Quality (cont.)
Bruce Thomson, Ph.D.
Effect of Intermittent Flow on Metals Mobilized from Native American Abandoned Uranium Mine Waste Sites
Sumant Avasarala
Column experiments were conducted to study the effect of intermittent flow on the mobility of metals from abandoned uranium mine waste sites in Blue Gap Tachee (BGT), Arizona and Laguna, New Mexico during surface water infiltration to groundwater resources. Intermittent flow represents the rainfall patterns in the southwestern United States, involving alternate wet and dry cycles. In order to simulate these rainfall patterns, shorter wet periods of 15, 30, 60, 120, and 360 minutes, followed by longer dry periods of 24 hours, were adopted for the column experiments. The experiment involved sequential leaching of sediments from Laguna and BGT with 18MὨ water (pH 5.4), synthetic rain water (SRW, pH 5.6), 10mM bicarbonate solution (pH 7.9) and 10mM acetic acid (pH 3.4) solution that represent the environmentally relevant conditions as witnessed in BGT water samples (pH 3.8 and 7.4). With just 18MὨ water and SRW almost 90 µg/L of U, 4500 µg/L of V and 20 µg/L of As were released from BGT mine waste while the Laguna sample showed the release of 380 µg/L of U, 2 µg/L of V, and 40 µg/L of As. The released U concentrations were 3-13 times its EPA MCL for U which under natural circumstances could threaten the proximate communities. Bicarbonate and acetic acid extractions on the other hand released 3500-6000 µg/L of U, 50-3000 µg/L of V, and 14-35 µg/L of As from both Laguna and BGT mine waste respectively. For reference, the columns were also leached continuously with bicarbonate and acetic acid for a week (each), to identify if the phases were kinetically or thermodynamically controlled. A 1D reactive transport model is also being applied to better interpret the role of these interplaying mechanisms.
Understanding Water Chemistry Under Uranium Recovery by In Situ Leaching for Aquifer Restoration
Omar Ruiz
From 1950 to the early 1980s, New Mexico played an important role in the production of uranium (U) for the nuclear power industry and the nation’s weapon programs. Though the U mining and milling industry is largely dormant at present, increased interest in nuclear power as a CO2 free power source has led to proposals for renewed development of U resources. In particular, U mining projects have been proposed using both underground mining and in situ leach (ISL) mining. The objective of this presentation is to investigate remediation methods that could possibly be implemented in New Mexico after ISL of U mining. In principle, ISL mining will minimize waste by eliminating mill tailings, mine waste rock, mine dewatering, and radiation exposure. ISL mining has not avoided environmental impacts and therefore an evaluation of complexation and redox reactions affecting the interactions between U minerals and co-constituents, which may include but are not limited to arsenic, chromium, molybdenum, selenium and, vanadium. Batch experiments of low-grade ore were conducted and show that U and co-constituents are dissolved and therefore need to be considered for aquifer remediation. Leach tests have been performed with acids to determine the total metal concentrations; NaHCO3 lixiviant was used to understand U and metal dissolution. Results from batch experiments have allowed an understanding of the effectiveness of ISL mining, and the potential impacts on groundwater quality. Remediation process will be composed of in-situ approaches that might include clean water flushing, DO depletion, chemical/bacteria reduction, and evaluating organic matter for positive or negative impacts on remediation. Abundant resources that are found through leaching experiments will be considered for remediation purposes. These results will be presented. These results will explain what processes could be potentially effective for aquifer restoration after ISL of U in New Mexico.
Aquifer Recharge
Matt Ely
Climate Change Impacts on Groundwater: More Than Just Drought
Bruce K. Daniels, Ph.D.
Most professionals recognize that a lack of precipitation (AKA drought) will impact groundwater recharge. It may be less known that the proportionality between changes of precipitation and recharge is typically not the same, i.e., 10% less precipitation would not yield 10% less recharge. To illustrate this distinction even further, we will show several precipitation climate examples which produce the same amount of annual precipitation, but when applied to hydrology models they surprisingly yield quite different reductions of recharge.
We have computed statistically significant trends in precipitation timing patterns from the decades of daily climate observations from many California stations. Applying just these timing trends to basin models, but without any change in total precipitation, we show how they surprisingly produce substantial recharge reductions, e.g., nearly a 7% recharge decrease over the next 30 years.
Changes of temperature alone can cause substantial impacts on groundwater recharge. Every degree Fahrenheit of temperature increase causes a 4% increase of evaporation. Since the ET fraction of total precipitation is often quite high at 50%–70%, then even a moderate increase in that evaporation would represent a considerable water loss. This is demonstrated by applying the predicted 7°F temperature increase to California groundwater basins to show those substantial impacts on groundwater recharge.
The predictions of California sea level rise are as much as 4½ feet. Coastal basins can only be protected from the additional seawater intrusion induced by this sea level rise by a corresponding rise of inland water levels. Such a protective action can be translated into a virtual loss of recharge, e.g., for a small coastal basin a loss of 500af per year for the next 85 years.
Tracking Deep Groundwater in Northwest New Mexico: Water Chemistry Evolution and Potential Recharge Implications
Erwin melis
Water quality data was utilized to construct a model across the southeastern Colorado Plateau (CP) to the Albuquerque basin (AB) using groundwater ages within the AB as residence times of the groundwater. This model was developed because to date no study has assessed the amount of recharge the San Andres-Glorieta (SAG) aquifer provides to the AB. Several groundwater flow models have suggested recharge contributes up to 25,000 acre-feet per year. Recharge amounts may determine how fast this deep aquifer is replenished as well as understanding the effects of pumping from the SAG aquifer since most of the 576 recently (2009) contemplated well sites listed in “notices of intention” filed with the New Mexico Office of the State Engineer are listing the SAG aquifer as target. Eighty percent of these notices of intention involve well sites within the transition zone between the AB and the CP, where relay ramps provide a complex network of connections between aquifers.
To build a representative model, we relied on existing USGS studies characterizing the SAG aquifer, utilized existing NMBGMR cross sections, and categorized geochemical data in order to develop a hydrogeological model of groundwater within the CP. The Plummer et al. (2004) dataset was utilized to constrain the final composition of the average groundwater sample in the western AB, whereas the evolution of a theoretical SAG groundwater sample was constrained by water quality sample data from the USGS NWIS. Our model suggests there is some variation in SAG aquifer water quality that could be explained by some groundwater moving quite fast, whereas older (and slower) groundwater may contribute the bulk of the salinity but not the volume. The groundwater flow to the AB may therefore be concentrated into several pathways; some that preferentially move along dominant (karstic) corridors within the Rio San Jose corridor.
To build a representative model, we relied on existing USGS studies characterizing the SAG aquifer, utilized existing NMBGMR cross sections, and categorized geochemical data in order to develop a hydrogeological model of groundwater within the CP. The Plummer et al. (2004) dataset was utilized to constrain the final composition of the average groundwater sample in the western AB, whereas the evolution of a theoretical SAG groundwater sample was constrained by water quality sample data from the USGS NWIS. Our model suggests there is some variation in SAG aquifer water quality that could be explained by some groundwater moving quite fast, whereas older (and slower) groundwater may contribute the bulk of the salinity but not the volume. The groundwater flow to the AB may therefore be concentrated into several pathways; some that preferentially move along dominant (karstic) corridors within the Rio San Jose corridor.
Aquifer Recharge (cont.)
Sara Chudnoff, PG
Applying Geochemistry to Managed Aquifer Recharge Projects
Christopher P. Wolf, PG
Managed aquifer recharge is being implemented at sites across the southwestern United States as an important water resource management tool, in order to recharge and store surplus water within aquifers, and to recover this water for later use. Compatibility of the recharged water with both groundwater and the aquifer matrix may be predicted using geochemical models and mixing calculations supported by site-specific data. Several examples from New Mexico will be presented, illustrating the use of geochemical techniques to predict the water quality of the recovered water, and to track recharged water in the aquifer.
In the Santa Rosa-Chinle aquifer system, the potential for reactions between treated surface water and the aquifer materials that would mobilize iron (Fe) and manganese (Mn) was evaluated, and the calculated saturation indices (SI) and oxidation reactions indicate that Fe and Mn solubility should be limited during recharge operations.
In the Tesuque Formation, fluoride concentrations were predicted to exceed the U.S. Environmental Protection Agency maximum contaminant level (MCL) in the recovered water based on fluorite solubility and mixing calculations. This information was used to identify treatment requirements for potable water use.
In the Santa Fe Group aquifer system, arsenic concentrations were initially diluted by the injected water but quickly rebounded during recovery, as a result of dissolving iron coatings on aquifer sediments releasing iron and adsorbed arsenic into solution. In another case, sulfur hexafluoride (SF6) was injected into the recharge water as a conservative tracer used to monitor recharge water movement in the aquifer. The SF6 tracer was observed in the monitor well network eight days after injection operations started, at a distance of 75 feet from the injection well.
These geochemistry studies provided critical information about the operation and treatment of waters recovered from these managed aquifer recharge systems.
Identification of Karst Groundwater Systems in the Pecos River Watershed and Salt Basin, New Mexico
Annie M. McCoy, CPG
Karst features in Permian carbonate rocks make up local and regional groundwater systems responsible for transmitting water through the Pecos River watershed in eastern New Mexico and the adjacent Salt Basin. The extent of the carbonate rocks has been well defined by geologic mapping and well drilling, but the role of karst features in collecting and increasing recharge and conveying groundwater has been poorly understood despite the fact that these features are responsible for conveying hundreds of thousands of acre-feet of water per year. Interpretation of topographic maps and high-resolution aerial photographs has provided new evidence for the location of local and regional karst groundwater systems in the Pecos River watershed and Salt Basin, but there are still large areas of the Pecos River watershed that have not been carefully evaluated and interpreted in this manner. Dissolution sinkholes have been identified in Permian carbonate rocks, collapse sinkholes have been identified in younger bedrock overlying Permian carbonate rocks, and subsidence sinkholes have been identified in unconsolidated alluvium overlying bedrock. Regional-scale “super sinkholes” up to 20 miles across enclosing smaller local-scale sinkholes have been identified. Review of historical aerial photographs and field studies have suggested that some sinkholes fill with water annually while others fill with water several times within a 10-year period. Infiltration rates vary widely depending on permeability of sediments on the floors of the sinkholes, and cavelike openings on the sides and floors of some sinkholes enhance infiltration.
Quantity and Location of Groundwater Recharge in the Sacramento Mountains, South-Central New Mexico
Geoffrey Rawling
The Sacramento Mountains and the adjacent Roswell Artesian Basin comprise a regional hydrologic system, wherein recharge in the mountains ultimately supplies water to the confined basin aquifer. Geologic, hydrologic, geochemical, and climatologic data were used to delineate the area of recharge in the southern Sacramento Mountains. The water-table fluctuation and chloride mass-balance methods were used to quantify recharge over a range of spatial and temporal scales. Extrapolation of the quantitative recharge estimates to the entire Sacramento Mountains region allowed comparison with previous recharge estimates for the northern Sacramento Mountains and the Roswell Artesian Basin. Recharge in the Sacramento Mountains is estimated to range from 159.86 to 209.42 × 106 m3/yr. Both the location of recharge and range in estimates is consistent with previous work that suggests that ~75% of the recharge to the confined aquifer in the Roswell Artesian Basin has moved downgradient through the Yeso Formation from distal recharge areas in the Sacramento Mountains. A smaller recharge component is derived from infiltration of streamflow beneath the major drainages that cross the Pecos Slope, but in the southern Sacramento Mountains much of this water is ultimately derived from spring discharge. Direct recharge across the Pecos Slope between the mountains and the confined basin aquifer is much smaller than either of the other two components.
Understanding Trace Organic Chemical Attenuation During Groundwater Recharge by Means of a 2D Synthetic Aquifer
Julia Regnery
The successful operation of a managed aquifer recharge (MAR) system must be based on a sound understanding of hydrologic, biological, and chemical processes, and their interactions, that are currently not understood to the point of providing useful predictions at all relevant scales of interest, especially regarding the attenuation of trace organic chemicals (TOrC). Attenuation of certain TOrC is highly dependent on key controlling conditions such as biodegradable dissolved organic carbon, redox conditions, and residence time in the subsurface. Although rate constants are considered useful to provide first estimates of the fate of TOrC at field-scale, which is essential for the design and operation of MAR sites, the question can be asked: How accurate rather simplified first-order rate constants are for model-based prediction of contaminant fate and transport considering the variability of environmental conditions.
We designed and constructed a laboratory-scale two-dimensional (2D) synthetic aquifer equipped with an array of automated sensors (temperature, water pressure, conductivity, soil moisture, oxidation reduction potential) and adjacent water and soil sampling ports to test and model fundamental subsurface processes that occur during MAR more closely representing field settings. This biologically active 2D synthetic aquifer consisting of technical sand and defined pockets of field soil measures 5 m long by 2 m tall and allows for simulation of an unsaturated infiltration zone and a saturated zone with underlying groundwater flow. Tracer experiments using conservative inorganic tracer as well as five spiked TOrC indicated significant differences in contaminant transport that were not explained by compound specific soil water distribution coefficients but related to the charge of molecules.
Aquifer Recharge (cont.)
Sara Chudnoff, PG
Forest Thinning to Increase Groundwater Recharge
Paul Davis
The State of New Mexico’s first approved basin water plan, for the Estancia Basin, recognized the fact that the basin is running out of groundwater. The Estancia Basin Planning Committee proposed thinning trees in the upland forests as one of their major efforts to increase recharge by eliminating transpiration from juniper and pinyon trees. EnviroLogic Inc. was tasked with performing a combined field/modeling study to quantify the increase in recharge associated with thinning. The field site contained contrasting landscapes of a pinyon/juniper forest and an adjacent open meadow. Soil moisture and temperature monitoring in trenches and boreholes were combined with a site weather station that monitored air temperature, precipitation, solar radiation, and wind speed and direction. Continuous monitoring for several years detected no significant response of deep soil moisture to precipitation in either the forest or the meadow. Unsaturated zone modeling based on 100 years of simulated weather combined with soil properties taken from trench and borehole samples indicated no recharge during the simulation period for either the forest or the meadow. In summary, neither the experiment nor the modeling supported the assertion that forest thinning increases groundwater recharge.
The Sacramento Mountains Watershed Study: Can Thinning Trees Increase the Water Supply?
Talon Newton, Ph.D.
Water is the limiting resource in New Mexico. Demand for this resource is primarily driven by population growth and agriculture, while supply is mainly driven by climate. Rain and snow in the high mountains feed streams and recharges local and regional aquifer systems. As the population continues to grow and under the pressures of climate change, water demand in New Mexico is going to increase while the water supply may actually decrease. While conservation practices are necessary to manage New Mexico’s water demands and uses, there may be ways of increasing the water supply. Thinning trees in mountainous areas, which improves wildlife habitat and reduces fire danger, may also have implications for increasing the groundwater and surface water supply. Much research over the last 50 years shows potential for tree thinning to increase water yield. However, hydrologic responses to thinning trees are highly variable and site specific. The New Mexico Bureau of Geology and Mineral Resources conducted the Sacramento Mountains Watershed Study, which took place in a high-elevation watershed in the Sacramento Mountains in southern New Mexico. This study, which focuses on assessing the effects of tree thinning on the local hydrologic system, analyzes each component of the soil water balance and how it responds to removing trees in the forest. More water reaches the ground due to a decrease in canopy interception. Surface runoff was not affected by the treatment. Net evapotranspiration (ET) does decrease when trees are thinned. However, soil water evaporation also increases. Results indicate that thinning trees may potentially increase local groundwater recharge. However, the complexity of the karstic aquifer system in the area makes it difficult to determine the magnitude of this increase in water supply.
Use of Direct Push Logging and Sampling to Characterize a Groundwater Recharge Plume
Wes McCall, PG
This presentation details field work to characterize groundwater in the area of a recharge basin located in an unconsolidated alluvial aquifer. Direct push logging techniques were used to differentiate recent groundwater recharge from background waters and to obtain samples for measurement of water quality indicator parameters to depths exceeding 90 feet. Logging and sampling at this site were performed using a groundwater profiling tool which gives simultaneous logs of soil electrical conductivity (EC) and hydraulic profiling tool (HPT) injection pressure as well as permitting multi-level groundwater sampling. The EC and HPT logs provided information about lithology and relative permeability to guide selection of sampling zones. Water quality parameters (specific conductance, pH, ORP, and DO) were monitored to stability as purging was conducted at each sample interval. This combined logging/sampling tool was used at several locations around the recharge basin to show the thickness of the groundwater recharge lens. Logs from this project clearly demonstrate the utilization of combined EC and HPT logs to identify the interface between recent recharge waters and background aquifer water, and between fresh aquifer water and intruding brines found at the base of the alluvium. The specific conductance data from the groundwater profile samples confirmed the HPT and EC log interpretation and provided additional data on water quality.
Aquifer Storage and Recovery
Matt Ely
ABCWUA Aquifer Storage and Recovery
Amy Ewing, P.G.
The Albuquerque Bernalillo County Water Utility Authority (ABCWUA) is implementing aquifer storage and recovery (ASR) projects for conjunctive management of surface water and groundwater resources using treated San Juan-Chama water diverted from the Rio Grande. The purpose is to recharge the Santa Fe Group aquifer system of the Middle Rio Grande Basin and to recover the water for later use.
Following successful implementation of a demonstration project using instream infiltration at Bear Canyon in 2008 and 2009, the full-scale project has been permitted by the New Mexico Office of the State Engineer. The first recharge event under the full-scale permit occurred in November 2014–March 2015, and the project will now be operated on an ongoing basis, with up to 3,000 acre-feet of water being recharged during winter months. Water is discharged into Bear Canyon arroyo and infiltrates through approximately 500 feet of unsaturated material (vadose zone) before reaching the aquifer.
The Water Authority is also working to develop additional recharge projects, including the Large-Scale ASR Project, which will establish a long-term drought reserve using treated surface water from the Water Authority’s drinking water treatment plant (DWTP). This project includes recharge demonstration using vadose zone and ASR wells at the DWTP. This presentation will provide an overview of the Water Authority’s ASR project operations and future plans.
Groundwater Mangement
Matt Ely
Spatially-Distributed Estimates of Groundwater Discharge to Streams in the Upper Colorado River Basin
Matthew Miller
The Colorado River has been identified as the most overallocated river in the world. Considering predicted future imbalances between water supply and demand, and the growing recognition that groundwater discharge to streams is critical for sustaining flow in streams and rivers, there is a need to develop methods to better quantify groundwater discharge to streams across large regions. We adapted and applied the spatially referenced regression on watershed attributes (SPARROW) water quality model to assess the spatial distribution of groundwater discharge to streams, the fraction of stream flow supported by groundwater discharge, and estimates and drivers of the amount of stream flow that originated as groundwater that is lost during in-stream transport in the Upper Colorado River Basin (UCRB). The model estimates an average of 1.8×1010 m3/yr of groundwater discharge to streams in the UCRB, greater than 80% of which is lost during in-stream transport to the Lower Colorado River Basin via processes including evapotranspiration and water diversion for irrigation. On average, 56% of the stream flow in the UCRB originated as groundwater. Observed relationships between groundwater discharge to streams and spring-time snow cover suggest that future changes in climate may result in decreased groundwater discharge to streams, but a greater reliance on groundwater for sustaining stream flow. Our results indicate that surface waters in the Colorado River Basin are dependent on groundwater discharge to streams, and that management approaches that consider groundwater and surface water as a joint resource will be needed to effectively manage current and future water resources in the Basin.
The Domestic Well Exemption in the West: A Case Study of Santa Fe's Municipal Ordinance
Maxine Paul
In the recent case of Bounds v. State of New Mexico, the New Mexico Supreme Court upheld the constitutionality of a statute that allows domestic wells to be permitted with less oversight than other water rights. The statute, known as the domestic well exemption, is common in various forms throughout the western United States. Currently, there are an estimated 200,000 permitted domestic wells across the state of New Mexico, increasing at a rate of approximately 5,000 per year. Various scholars have argued for amendments to domestic well statutes or local regulations to make exempt well applications as rigorous as other water right applications. In consideration of local solutions, this study addresses one of the few municipal ordinances and three important controversies in domestic well management: the interaction between domestic well pumping and other water uses, the longevity of groundwater sources, and the “development loophole.” The City of Santa Fe’s domestic well ordinance is found to indirectly address concerns related to aquifer use and conservation; however, restricting well uptake in threatened areas that speak to specific, measurable goals, aligned with accurate databases, may better serve municipalities and counties in New Mexico as they do in other states.
Use of Groundwater and Surface Water Fluctuations to Estimate Evapotranspiration
James Syme
An important component of groundwater resource management is the knowledge of water removed from the system by evapotranspiration. In this study, estimates of evapotranspiration in northwest New Mexico were derived from fluctuations of groundwater levels in piezometers and from fluctuation in streamflow. Fourier analysis was used to separate and quantify the daily fluctuations caused by evapotranspiration from other potential causes of diurnal fluctuations. For surface water, the resulting fluctuations were directly integrated to yield estimates of daily evapotranspiration. For groundwater, the resulting fluctuations were combined with a one-dimensional groundwater flow model to yield daily estimates of evapotranspiration. Analysis of the daily evapotranspiration estimates over time revealed a systematic change in evapotranspiration throughout the year.
Keynote Address: Challenging Times Ahead in Hydrology
Daniel B. Stephens, Ph.D., PG
Mining Impacts on Groundwater Quality
William Alley, Ph.D.
Assessing Background Groundwater in the Uranium Mining Belt of Northwestern New Mexico
Tom Myers, Ph.D.
Northwestern New Mexico has experienced substantial uranium (U) mining and milling since the 1950s. This activity has left a legacy of groundwater highly contaminated with U and other contaminants near closed mills where unlined tailings impoundments were constructed over shallow alluvial aquifers. As efforts proceed to remediate these aquifers, the question of what is natural background arises because that is often the remediation goal. Under the tailings in Grants, New Mexico, U concentrations once exceeded 100 mg/L while downgradient in nearby subdivisions advection from the tailings caused the U concentration to increase to over 0.1 mg/L, or three or more times the drinking water standard of 0.03 mg/L. Comparison of conceptual flow models for pre-milling, mill operations, and post-mill operations shows flow paths have changed substantially due to the discharge of highly contaminated mine dewatering water upstream of the site and the mounding of seepage under the tailings pile. Groundwater advection of infiltrated mine dewatering discharge could not have affected U concentrations at the millsite because it would have taken more than 80 years. Also, U has a high retardation in alluvial soil which would increase the time for transport to almost 400 years, and U attenuates or becomes bound in the soils. Groundwater mounding during millsite operations likely caused a flow reversal in the groundwater just upgradient from the millsite which explains the observed trends in U concentrations in wells above the millsite. Advection and dispersion from the millsite caused U to affect groundwater as much as half a kilometer above the millsite. Historic U concentrations that precede mil site contamination match those observed in unaffected groundwater sampled in regional studies and accurately reflect nearby groundwater concentrations. There is no evidence that natural sources cause any observed spikes in the U concentration.
Use of Chemical and Isotopic Identifiers to Characterize a Uranium Contaminated Groundwater Plume in New Mexico
Mitchell Schatz
Groundwater in shallow aquifers near Milan, New Mexico is the major source of water for agriculture and human consumption. Since 1983, groundwater in the region has high levels of uranium, selenium, nitrates, and vanadium, and determined to be too contaminated for human use, and other sources of water have been provided to the region. Isotopic and chemical identifiers were used to help distinguish contaminants derived from anthropogenic and natural occurring sources near a former uranium mining and milling site near Milan. Private wells near the uranium disposal site were sampled in the fall of 2015 and compared to mill-derived groundwater from a former uranium mill site and known natural groundwater sources in the area. Principal Component Analysis was used to display similarities and differences in groundwater chemistry for sampled wells, natural sources, and uranium mill site groundwater. Several of the private wells had similar levels of contaminants as mill-derived water. Activity ratios (ARs) for uranium-234 and uranium-238 were compared to naturally derived groundwater, where recent studies show mill-derived groundwater ARs are near secular ratios of 1 and natural derived groundwater have ARs values above 2. Leaching of the mill tailings involved the use of sulfuric acid and other leaching agents. Dissolved sulfate in mill-derived groundwater was enriched with sulfur-34 whereas natural occurring groundwater showed a depletion of sulfur-34. Other stable isotopes were used to determine sources of recharge in the aquifers. The use of chemical and isotopic identifiers in this study help to determine that groundwater contaminants in private wells downgradient from the milling site were most likely derived from the mill site dewatering activities and not the natural occurring contaminants from Morrison formations in the San Mateo Creek basin aquifers.
Non-Traditional Water Resources
Sara Chudnoff, PG
Brackish Water for Inland Water Supply: Hydrologic Challenges
Bruce Thomson, Ph.D.
Increasing demand for scarce water supplies in the arid southwestern United States has led water managers to consider alternative sources of water for municipal and industrial supply, including wastewater reuse and development of brackish and saline groundwater resources. In New Mexico there has been considerable interest in brackish groundwater development because of its widespread distribution over much of the state and because its use was not regulated prior to 2009. There are several characteristics of brackish water aquifers that make development of this resource much more difficult than seawater desalination. From a hydrogeological perspective these are: (1) uncertainty regarding the magnitude of the resource, (2) challenges of recovery water from deep low productivity aquifers, (3) identifying methods of desalination concentrate management, and most importantly, (4) recognizing and addressing issues regarding the sustainability of the resource. There is very little information on magnitude of brackish waters resource or its quality because it had no value until recently. Using estimates of hydraulic properties from available studies, it can be shown that development of this resource will be difficult and costly. In particular, low values for conductivity and storage coefficient mean that wells will require very large spacing, produce large drawdowns, and will have larger pumping costs than current supply wells. These hydraulic properties will also have consequences for concentrate disposal as tight formations will require multiple wells for waste injection. Finally, most brackish water aquifers in New Mexico receive little or no recharge. Development of groundwater from them is not sustainable in that it will result in rapid depletion of the resource. An example will be presented in which a proposed urban development, one of several proposed near Albuquerque, would deplete the entire resource in 20 to 70 years.
Brackish Water Resources and Recharge Rates in the Capitan Reef Aquifer, Southeastern New Mexico and West Texas
Lewis Land
The Capitan Reef is a Permian-age karstic limestone aquifer that encircles the Delaware Basin in southeastern New Mexico and west Texas. The reef aquifer is the principal source of fresh water for the city of Carlsbad, New Mexico. However, throughout most of its extent water in the reef is too saline for human consumption. Both the petroleum industry and potash mining industry have recently expressed interest in exploiting brackish water resources in the reef aquifer for water flooding mature oil fields and processing potash ore. The impact of brackish water withdrawals on fresh water resources near Carlsbad and baseflow into the Pecos River is thought to be minimal, because of a partial hydraulic barrier that inhibits communication between the western and eastern segments of the reef. This hydraulic barrier is attributed to low-permeability sediment deposited in submarine channels that cut across the reef during middle Permian time. Water levels in the eastern segment of the reef aquifer declined by several tens of meters through the 1970s and 1980s because of withdrawals by the petroleum industry, as measured in a series of monitoring wells installed by the U.S. Geological Survey. However, in the past three decades water levels in the eastern segment have risen by >100 m, raising questions about rates and sources of recharge to the reef.
Characterizing Brackish Water in New Mexico
Stacy Timmons
Recurring severe droughts in New Mexico require consideration of non-traditional water resources, including brackish water. However, better characterization of this resource is needed. In New Mexico, brackish water resources have been cited for decades as extensive and readily available, with as much as 75% of the state’s groundwater estimated to be brackish or saline water. Brackish water resources (1000-10,000 ppm TDS) are largely found within regional basins, incorporating geology complicated by rift basin faulting, episodic volcanism, and extensive deformation. The diverse geology creates regional and local variability in water chemistry, as well as with depth. Complete and accurate datasets are required to promote research on water resources, across the various stratigraphic units and among fresh, brackish, and saline waters. The general goal of the Aquifer Mapping Program at the New Mexico Bureau of Geology and Mineral Resources is to characterize all of the state’s aquifers in terms of water quality, quantity, and distribution. Currently, we are undertaking a fundamental step in characterizing New Mexico’s brackish waters through a major water quality data compilation effort. In addition to our own data, the datasets and databases will incorporate data from the New Mexico Environment Department, the New Mexico Office of the State Engineer, the U.S. Geological Survey, municipalities, consultants, and researchers. Historic data that has previously only been available in printed reports is also being digitized and incorporated into these datasets. This effort will lead to improved water quality data availability for the state, identification of target regions for brackish water use based on geologic and hydrologic data, and improved understanding of possible interconnections of fresh and brackish water resources. These efforts also will shed light on spatial and chemical data gaps.
Panel: Water Quality - Constituents of Concern
Laura Bexfield
Poster Session
Changes in DOM Quantity and Quality in a Southern Rockies Forested Catchment
Galveston Begaye
Forest fires change the processes governing dissolved organic matter (DOM) transport. These shifts may result in adverse water quality impacts in headwater catchments and on receiving water bodies downstream. DOM is a key control on water quality and DOM provides nutrients that are consumed by the surrounding ecosystem. In order to investigate how DOM in the hydrologic system is impacted by a forest fire, data from three catchments in the Valles Caldera National Preserve were examined. This study sought to address two research questions. First, after a forest fire occurs, is there a significant impact on DOM quantity? Second, how does DOM quality vary in response to catchment processes and post-fire processes? Source water mixing analysis was combined with cutting edge DOM indices analysis using fluorescence excitation–emission matrix spectroscopy (EEMs). Source water mixing results identify groundwater contributions from short and long residence time waters as the predominant sources of water to streams in the Valles Caldera. The relative source water compositions identified as present in the stream were used to develop calculated DOM quality indices in the stream. These calculated compositions consistently showed expectations that were less ‘humified’ and less ‘microbially processed’ than observed compositions. These pre-fire results indicate that DOM is consumed, likely by microbial processes, between the source water locations and the location of stream observations. The shift in index values indicates that these consumption processes remove relatively labile DOM and leave behind more recalcitrant DOM with a ‘humic-like’ signature. In the post-fire period this pattern continued but with significantly higher DOM and more humic DOM index values. Enhanced aromaticity of DOM suggests that some of this humic signature enhancement may result from solubilization of biochar.
Physiochemical Studies of Biofilm Growth on 3-D Printed Nanosurfaces Towards Improved Wastewater Treatment
Philip Roveto
Bacterial conglomerations, or biofilms, are of utmost concern in many fields, including material manufacture, biomedicine, and water and wastewater treatment. Biofilms form through the processes of adhesion, growth, and dispersal, yielding communities with dramatically increased lifespans and biocide resistance. Municipal wastewater and natural waterways both can contain high concentrations of ammonia and phosphorus that can provide nutrients for algal growth, leading to ecosystem asphyxiation. Nitrifying biofilms are increasingly used in wastewater treatment plants for ammonia removal, as biofilms are conducive to the survival of these slow growing heterotrophs.
Our research is focused on developing a better understanding of how attachment surface geometry and chemistry affects biofilm structure and function. We are evaluating high surface-area surfaces composed of acrylonitrile butadiene styrene (ABS), poly-lactic acid (PLA), and nylon plastics fabricated with 3-D printing technology, which include hundreds of miniature wells (1 mm)3 for bacterial colonies to grow. The plastic surfaces were laminated with a series of covalently cross-linked polymeric layers, alternating between commercially available polyethyleneimine (PEI) and synthesized poly-dimethylazlactone (PDMA). A terminal layer containing residual azlactone rings was then further modified by attaching spermine, a long-chain nitrogen-rich substrate, to create a physio-chemical nanosurface potentially capable of increasing bacterial adhesion.
A series of bioreactors were designed to provide consistent environmental conditions for untreated and modified surfaces. Constant aeration provided sufficient dissolved oxygen levels, and a well-buffered synthetic nutrient source provided inorganic carbon in the form of bicarbonate, ammonia, a metabolic energy source for the nitrifying bacteria, and additional biologically necessary nutrients. Colony health was measured by nitrification rates, based on ammonia removal. Early results show the corresponding rate of chemical transformation per unit of surface area increased 3-4 times over the course of one month to 3 g/m2/d of ammonia.
The People by the River
Leo S. Leonhart, Ph.D., RG
The Mojave Indians (Pipa Aha Makav aka “The People by the River”) have inhabited the Mohave Valley since “time immemorial.” Historically, their presence extended over an area straddling the Colorado River from Lake Mohave ~15 mi north of Davis Dam and south to the Needles Peaks. Now officially known by the federal government as the Fort Mojave Indian Tribe (“FMIT”), Mojaves first encountered western civilization in the 16th century, when Spanish explorers first entered the area. Today, as a result of various governmental interventions, tribal members inhabit two reservations along the river. The northernmost, FMIT Reservation, comprises a “checkerboard” of parcels in Nevada, Arizona, and California and totaling ~51 mi2. Another group of Mojaves reside on the Colorado River Indian Tribes (“CRIT”) Reservation, which, in addition to the Mojaves, comprises a federation of Chemehuevis, Hopis, and Navajos. The CRIT reservation is approximately 40 mi south of the FMIT Reservation and covers approximately 460 mi2 straddling the Colorado River in Arizona and California, below Parker Dam. As landowners along the river, both tribes hold rights to divert water in amounts established in protracted litigation before the Supreme Court (Arizona v. California, 1963, et seq.). Presently, FMIT holds rights to an annual allocation of 132,789 AF, and the CRIT to a diversion of 719,248 AF, representing more than 30% of Arizona’s allocation.
This paper addresses the FMIT’s water resource challenges, including issues related to both water supply and water quality. For the FMIT, the latter issue arises as a result of ongoing actions to remedy a groundwater plume of hexavalent chromium from the Topock Compressor Station, south of the FMIT Reservation and on grounds highly sacred to the Mojaves. This matter has created profound conflicts between the need to preserve traditional tribal values and to remedy a serious environmental threat.
Sustainabliity and Resilience
Bruce Thomson, Ph.D.
Aquifer Compaction and Land-Surface Elevation Change in the Albuquerque Basin from 2005 to 2014
Jessica Driscoll, PhD
Sustained groundwater withdrawals for municipal and agricultural uses in excess of recharge have resulted in seasonal (elastic) land-surface subsidence and permanent compaction of silt and clay layers in alluvial basins in the southwest United States. Water supply for the Albuquerque Basin has historically been met nearly exclusively by groundwater withdrawal from the Santa Fe Group aquifer, resulting in water-level declines in the aquifer system. Reduction of groundwater pumping for municipal water supply after the San Juan-Chama Drinking Water Project in 2008 has resulted in aquifer recovery. Global Positioning System (GPS) survey techniques and satellite-based Interferometeric Synthetic Aperture Radar (InSAR) were used to measure land-surface elevation over a variety of timescales to quantify land-surface elevation before and after groundwater-level recovery, and compared with previous studies. An established Land Subsidence Survey (LSS) network of 43 monuments around the study area was surveyed using network-based differential GPS techniques in 1994 and 2005, and OPUS rapid-static occupation techniques in 2014. InSAR was used to measure subsidence in the Albuquerque Basin between 2005 and 2010, spanning the change in water source for the City of Albuquerque supply. InSAR images were combined to create composite land-surface elevation change maps over different time intervals. GPS and InSAR results show spatially heterogeneous land-surface elevation change within the Albuquerque Basin. The magnitude and direction of elevation changes of the LSS benchmarks were not consistent between 1994 to 2005 and 2005 to 2014. InSAR results from 2005-2010 indicate both seasonal and longer-term elevation changes. Some locations show seasonal subsidence of about 15 millimeters (mm) during timespans when groundwater levels were declining, such as near Rio Rancho. Generally, InSAR data from selected points in the Albuquerque metro area show uplift of up to 20 mm from 2005-2010, where groundwater-level recoveries were also measured.
Assessment of Potential Gila River Flow Alteration on Riparian Groundwater Conditions
Deborah L. Hathaway, PE
Groundwater modeling was conducted to assess effects of potential diversions from the Gila River in New Mexico, pursuant to the authority and constraints of the Arizona Water Settlements Act (AWSA) of 2004, on riparian groundwater conditions. Among concerns were the effects of flow alteration on riparian vegetation in the Cliff-Gila Valley. Defining the relationship between the hydrograph, existing and altered, and groundwater is a critical step in characterizing the flow-ecology relationship for groundwater-dependent riparian vegetation under the wide range of existing flow conditions and with potential diversions. The assessment is streamlined through focus on periods and conditions of largest potential change identified through flow alteration statistics using The Nature Conservancy’s Indicators of Hydrologic Alteration (IHA) software, and examination of effects over periods associated with vegetation recruitment and early growth. Framed accordingly, hypothetical flow alteration scenarios are simulated with a high-resolution groundwater model incorporating a boundary condition supporting flow-dependent stream stage and width. Simulated groundwater depths and changes under baseline and altered hydrographs illustrate effects of potential diversions on groundwater within the topographically diverse riparian zone and provide a foundation for evaluation of questions regarding implications for groundwater-dependent riparian vegetation.
Groundwater Sustainability in Mesilla Basin–Rio Grande Valley Area, USA and Mexico—A Hydrogeologic Perspective
John Hawley
With the exception of recharge from the Rio Grande and a few high-mountain areas, sustainable groundwater resources in the binational Mesilla Basin and Valley region of New Mexico, Texas, and Chihuahua (Mexico) are primarily replenished by underflow from local sources that are predominantly brackish. In this respect, all (surface and subsurface) waters in the fresh to moderately brackish range (<10,000 mg/L) are here considered as assets rather than liabilities. Thick intermontane-basin fill of the Upper Cenozoic Santa Fe Group and thin fluvial deposits of the Late Quaternary Mesilla Valley corridor constitute the primary aquifer systems. Locally, however, bedrock terranes also provide significant secondary groundwater reservoirs. The latter include carbonate and evaporitic rocks of Permian and Mesozoic Age, and Lower to Middle Tertiary sedimentary and volcanic rocks. In central-basin and inner river-valley areas of primary interest, the most productive aquifers comprise as much as 300 m of sand-dominated lithofacies that include thick ancestral Rio Grande deposits. For an aquifer system with an area of 2700 km2 and 300 m average thickness, a conservative estimate of the amount of economically-recoverable fresh to slightly brackish groundwater (<5,000 mg/L tds) is about 80 km3 (65 million ac-ft). Basic assumptions include: unconfined to leaky-confined aquifer conditions, a specific yield (Sy) of 0.1, long-term increase in storivity (S) from a 1 x 10-4 base value to one approaching the Sy range, and recognition of a potential for significant land subsidence in some places. These conclusions are based on recent hydrogeologic-framework model updates in the Mesilla Basin and surrounding basin/range areas as part of the ongoing interdisciplinary, multi-institutional Transboundary Aquifer Assessment Project coordinated by the NMWRRI. Emphasis is on digital characterization of lithofacies distribution, hydrostratigraphy, and structural-boundary conditions. Three-D, hydrogeologic map and fence-diagram compilation scale is 1:100,000, and model-base elevation is Mean Sea Level.
Surveying New Mexico’s Private Well Users About Well Characteristics and Water Testing Practices
Kathryn Hayden
Little is known about private water well characteristics and water testing practices of private, domestic well users in New Mexico. The New Mexico Environment Department (NMED) has been conducting free testing events for private domestic well owners since 1982. Through interactions with well users and basic surveys conducted at the events, NMED has been able to gain some insight into testing practices and well characteristics. However, surveys conducted during the events prior to 2014 were limited, only containing questions about the marketing, dates, and times of the events. In 2014 the New Mexico Environment Department, in conjunction with the New Mexico Department of Health (NMDOH), began conducting more detailed surveys to better understand the characteristics of private wells in New Mexico and the individuals who rely on them for drinking water. In addition to information about event marketing, dates, and times, NMED and NMDOH began collecting information about water testing behaviors of well users, including when well users last tested water from their wells; the analytes for which well users previously had their well water tested; and any reasons for not testing well water for a variety of analytes. The new surveys also request more detailed information about well characteristics including locations, construction materials, depths, and suspected concerns. This presentation is an analysis of the results of the new surveys administered by NMED and NMDOH at water testing events, along with a summary of how this information will be used in the future.
Sustainabliity and Resilience (cont.)
Bruce Thomson, Ph.D.
Creating Simple Communication About Groundwater and Health Is Not Simple To Do. Why It Is Worth It.
Deyonne Sandoval, MS CHES
Most people will say having clean, running water is important to their health; yet, they do not have the time or energy to figure out the details of water quality. The average person will not wade through dense technical reports or sift through complicated data, no matter how concerned they are. Consumers have conveyed they want the information packaged in a memorable fashion and in a format conducive to quick reading. Health promotion professionals know it is ideal to begin health communication campaigns with a simple, memorable message to initially influence a health behavior. Here is the challenge: creating a simple message for a general audience is not easy to do. Groundwater is complex. Geology, especially in New Mexico, is complex. Health promotion is complex. The process of crafting concise yet accurate, useful, and memorable groundwater health messages for a general audience is a delicate and lengthy process. This presentation examines (1) the steps the New Mexico Environmental Public Health Tracking program has taken, working with the New Mexico Private Well Program, to create messages about complicated water quality topics, well testing, and health protection; and (2) lessons learned about the message development process.
Private Well Outreach at Bernalillo County, What We Have Done and Where We Are Going
Sara Chudnoff, PG
Bernalillo County, located in central New Mexico, encompasses 1,160 mi2 and has a population of 662,564 (2010 census). The majority of the population resides within the City of Albuquerque and its adjacent areas which are served by a local water utility that uses both groundwater and surface water. Within those adjacent areas, there are a few smaller areas that rely on domestic and shared wells, such as the North Albuquerque Acres (NAA). East of Albuquerque are the Sandia and Manzano Mountains, and a community on the other side of the mountains locally referred to as the East Mountain Area (EMA). The population in the EMA depends solely on groundwater, with roughly 53 percent of the population relying on domestic wells.
All wells within Bernalillo County are permitted by the Office of the State Engineer (OSE) or by the OSE and the county. The county’s Natural Resource Services (NRS) section through its outreach efforts to domestic well users helps to raise their awareness of water quantity and water quality. Through the NRS residents can participate in free water testing, free well education classes, the Water Level Monitoring Program to help them better understand the aquifer system, and learn how to properly care for their wells (from applicable regulations to sampling and disinfection). To achieve these efforts, the county collaborates with several agencies including the State of New Mexico’s Department of Health, Environment Department, Bureau of Geology, and the OSE.
This presentation is an overview of the county’s outreach efforts to domestic well users, a summary of responses from the residents who participate in that outreach, and the ongoing collaboration among the involved agencies.
Water Quality
William Alley, Ph.D.
Assessing Variability in Groundwater Quality in the San Joaquin Valley, California with Continuous Monitoring
Justin T. Kulongoski
In an effort to better understand how groundwater quality changes over short (daily to monthly) and long (seasonal to decadal) timescales, the USGS NAWQA Program collects continuous (high frequency) data on water quality in near real time at three wells in the San Joaquin Valley, California, USA. The water-quality parameters pH, temperature (T), dissolved oxygen (DO), and specific conductance (SC) are measured (30-minute intervals) at continuously pumping wells (190 m and 98 m depths), and the data are transmitted hourly to the National Water Information System online database for near real time viewing. Nitrate (NO3) also is measured optically at the deep well and the data transmitted. A monitoring well (71 m depth) is instrumented to pump once per day, measure T, DO, pH, and SC, and transmit the data.
Groundwater also is sampled bimonthly at each well for nitrate (NO3), DBCP (Dibromochloropropane), perchlorate, δD, δ18O, 3H, 14C and major ion in an effort to correlate changes in pH, T, DO, SC, and NO3 with these constituents of interest. NO3, DBCP, and perchlorate were detected above maximum contaminant levels or at elevated concentrations in the shallower two wells.
The first years of data (2013-2015) show mostly constant groundwater quality in the deep well (190 m), which suggest that the deep aquifer is isolated from surface activities by low groundwater flow. This agrees with non-detectable 3H and low 14C activities in the deep groundwater. However, the shallow wells (98 m and 71 m) show increasing SC, NO3, and uranium levels, and have high 3H and 14C activities, suggesting more rapid communication with recharge at the land surface.
Hexavalent Chromium in Groundwater in the Davis/Dixon/Woodland Area, Western Sacramento Valley, California
Mary Stallard, PG, CEG, CHG
Elevated groundwater hexavalent chromium concentrations not known to be associated with environmental releases are found throughout the Davis/Dixon/Woodland area of the Western Sacramento Valley. As part of an effort to establish groundwater background (ambient) values for a federal Superfund site in Davis, data have been compiled from available public databases and several other sources. Ambient hexavalent chromium concentrations exceeding 200 micrograms per liter (µg/L) have been identified locally in the first hydrostratigraphic unit (HSU-1), a low-to-moderate permeability zone extending from the water table to approximately 80 feet below ground surface (bgs). Ambient concentrations as high as 180 µg/L have been reported in the next deeper unit (HSU-2), a high permeability zone extending from approximately 80 to 120 feet bgs and used extensively for water supply. Concentrations can be highly variable over short distances, especially in HSU-1. The combination of ultramafic sediments derived from the Coast Ranges to the west and oxic/slightly alkaline groundwater allow for the natural oxidation of trivalent chromium to hexavalent; however, the mechanism(s) that produce the wide range and spatial variability of ambient hexavalent chromium concentrations in the area are not well understood. Scientists from the U.S. Geological Survey, Stanford University, University of California Davis and its contractors have been investigating potential mechanisms, including: (1) geochemical changes associated with organic matter, fertilizer use, widely fluctuating water levels, and irrigation; (2) hydrologic factors such as residence time and mixing; and (3) geologic factors such as mineralogy. This presentation will review the regional hexavalent groundwater data and available results related to potential formation mechanisms.
Water Quality (cont.)
William Alley, Ph.D.
Building a Robust Conceptual Site Model for Remedy Optimization of a Former Dry Cleaner Contaminant Plume
Michael Lamar, PE
Groundwater beneath and downgradient from a former dry cleaner contains elevated concentrations of tetrachloroethene (PCE), including dense non-aqueous phase liquid (DNAPL). In 2008, a remedial action was implemented in the source area that included in situ bioremediation using a groundwater recirculation strategy to distribute amendment. The remedy resulted in groundwater concentration reductions greater than 95% on average; however, PCE concentrations remained elevated in discrete areas in situ. The conceptual site model was thus considered incomplete and additional information including the vertical and lateral extent of residual DNAPL and impacts of matrix diffusion on plume contaminant loading and longevity was necessary to inform decisions about technology implementation and optimization.
Historical investigation efforts indicated that the subsurface geology was highly heterogeneous with a stratified, high permeability sand and gravel upper aquifer underlain by a lower permeability stratified sand, silt, and clay in the lower portion of the shallow aquifer. Observations from existing monitoring wells suggested that the stratified geology and low permeability layers likely resulted in both heterogeneous vertical distribution of DNAPL in the source area and sorbed mass is diffusing into the dissolved phase plume, acting as secondary sources of contamination. Therefore, the source area recirculation treatment system was primarily delivering amendment to the higher permeability groundwater, resulting in effective treatment in the transmissive zones, but contaminant mass in the low permeability layers was not as effectively treated.
A post-remediation site investigation was performed to evaluate PCE mass distribution vertically and assess the magnitude of residual, sorbed, and diffused mass in the stratified soils. A TRIAD approach was applied using a mobile laboratory for fast-turnaround PCE data in both groundwater and soil. The results from this investigation profoundly changed the conceptual site model and will be used to determine the most appropriate next steps for remedy optimization of this PCE plume.
Quality of Groundwater Used for Public Supply in the Basin and Range Basin-Fill Aquifers, Southwestern U.S.
Marylynn Musgrove
The Basin and Range basin-fill aquifers underlie a large area of the southwestern U.S. and are extensively and increasingly used for public supply. The aquifers consist primarily of thick unconsolidated to semi-consolidated gravel, sand, silt, and clay deposits in sediment-filled alluvial basins bounded by mountain ranges. In 2013, the National Water-Quality Assessment (NAWQA) Program of the U.S. Geological Survey began a sampling effort focused on the quality of groundwater used for public supply in principal aquifers across the nation. The Basin and Range basin-fill aquifers rank fourth among the nation’s principal aquifers for groundwater withdrawal for public supply. NAWQA sampled 78 public-supply wells in the Basin and Range basin-fill aquifers in Arizona, California, Idaho, Nevada, and Utah in 2013. Samples were analyzed for a comprehensive suite of water-quality constituents including major and trace elements (including hexavalent chromium), nutrients, pesticides, volatile organic compounds, radionuclides, microbial indicators, pharmaceuticals, hormones, and groundwater age tracers. The most common exceedances of water-quality benchmarks were for salinity-related constituents: 35% of samples had high concentrations of dissolved solids, chloride, and (or) sulfate, relative to secondary standards. The most common exceedance of human-health benchmarks for drinking water was for arsenic (13%). Exceedances for uranium (3%) and nitrate (0%) were low; these results contrast with previous NAWQA studies of shallow groundwater in these aquifers, where exceedances of human-health benchmarks for constituents such as arsenic, uranium, and nitrate occurred more frequently. Results are being evaluated to assess the relation of water quality with natural and human-related factors. Most constituents that have exceedances of water-quality or human-health benchmarks in the Basin and Range basin-fill aquifers are derived from geologic sources, and generally are observed at higher concentrations in older, more geochemically evolved groundwater.