2007 Ground Water Summit

Tuesday, May 1, 2007 : 2:30 p.m.

Coupled Mixing-Cell and Mass Balance Flow Path Models of the White River Flow System, Nevada

F. Emile Sawyer, B.S., Env, Geolo, James M. Thomas, Phd., Hydrology, Sam Earman, Phd., Hydrology and Rosemary Carroll, M.S, Hydrology, Desert Research Institute

In a continuing effort to characterize the White River Flow System (WRFS), in east-southeast Nevada, three mass balance models were developed using δD and δ18O as tracers to evaluate recent recharge-discharge estimates and likely flow paths of regional groundwater flow in the WRFS. A statistical analysis of model realizations assessed the viability of hypothesized flow paths and estimated recharge and discharge values. Four variations were considered for each of the three proposed models. The modeling showed that only two of the four proposed model scenarios were realistic. Preliminary results of observed versus modeled δD values at regional springs indicate that proposed flow volumes and paths are reasonable for the WRFS, with the exception of proposed flow paths to the regional springs in Pahranagat Valley, in the middle part of the flow system. Modeled δD and δ18O values for all regional springs in the WRFS, except for Pahranagat Valley, are within ± 2‰ and ± 0.02‰, for δD and δ18O, respectively. In Pahranagat Valley modeled δD and δ18O values are much greater than ± 2‰ and ± 0.02‰, indicating that the models for this part of the WRFS are not correctly conceptualized.

1: Desert Research Institute, Reno, NV, USA

 

F. Emile Sawyer, B.S., Env, Geolo, Desert Research Institute Emile Sawyer is a Graduate Research Assistant at the Desert Research Institute in Reno, Nevada. He is enrolled in the Hydrologic Sciences Program at the University of Nevada-Reno and intends to graduate with an M.S. in Hydrogeology in May 2007.

James M. Thomas, Phd., Hydrology, Desert Research Institute Dr. Thomas' general research interests include hydrogeology, water chemistry, age dating groundwaters, groundwater recharge and discharge processes, watershed hydrology and chemistry, evaluating water resources, and water resource potability and sustainability in developing countries. My research is primarily in three geographic areas: 1) northern Nevada watersheds, particularly the Lake Tahoe and Walker Lake watersheds; 2) southern and eastern Nevada; and 3) West Africa.

Sam Earman, Phd., Hydrology, Desert Research Institute Dr. Earman's research is focused on using natural tracers to investigate groundwater systems. Dr. Earman collaborates with researchers at the New Mexico Instiute of Mining and Technology, the University of Wisconsin-Madison, Los Alamos National Laboratory, the U.S. Fish and Wildlife Service, and the U.S. Geological Survey. RESEARCH AREAS: Natural tracer applications in hydrology (including major ions, 18O/2H, 14C, and 3H); Recycling of precipitation in the Great Basin; basin-scale chemical evolution of groundwater; groundwater in mountains and mountain-basin transfer of groundwater; the importance of snowmelt to groundwater recharge; and possible impacts of climate change on groundwater resources in the western USA.

Rosemary Carroll, M.S, Hydrology, Desert Research Institute Ms. Carroll's research focuses primarily on numeric simulation of hydrologic systems. Her thesis work provided an opportunity to model mercury transport and fate along the Carson River. To appropriately model this system, extensive modification was made to the codes describing hydraulics (RIVMOD) and water quality (WASP5, MERC4). Monte Carlo simulations were then conducted to examine uncertainty in parameter values as well as uncertainty in the model's ability to predict future system behavior. Subsequent research at DRI has focused on developing a coupled surface-subsurface model (EPIC-MODFLOW) to describe hydrologic response in semi-permanent and temporary wetlands to changing climatic conditions. Time series analysis permitted hindcasting beyond model capabilities to allow one to hypothesize of the likeliness of droughts, floods and regional climatic trends. Ms. Carroll's research focuses primarily on numeric simulation of hydrologic systems. Her thesis work provided an opportunity to model mercury transport and fate along the Carson River. To appropriately model this system, extensive modification was made to the codes describing hydraulics (RIVMOD) and water quality (WASP5, MERC4). Monte Carlo simulations were then conducted to examine uncertainty in parameter values as well as uncertainty in the model's ability to predict future system behavior. Subsequent research at DRI has focused on developing a coupled surface-subsurface model (EPIC-MODFLOW) to describe hydrologic response in semi-permanent and temporary wetlands to changing climatic conditions. Time series analysis permitted hindcasting beyond model capabilities to allow one to hypothesize of the likeliness of droughts, floods and regional climatic trends. Ms. Carroll is currently pursuing her Phd. in Hydrology.


The 2007 Ground Water Summit