Developing a Groundwater Model:
Spanish Springs Valley, Nevada

Spanish Springs Valley is a few miles northeast of Reno, Nevada and lies between the Sierra Nevada on the west and the rocky plateaus of the Pah Rah Range to the east. Within the valley are two large lakes fed by seven natural warm springs, surrounded by abundant wetlands. This habitat is home to a variety of species including the red-tailed hawk, American white pelican, the great horned owl, Canada geese, and many other waterfowl and shorebird species. Spanish Spring Valley was the location of various ranch and farm operations, including the ranch owned by one of Nevada's most infamous mining and banking tycoons, George Wingfield.

Rapid population growth in the Reno-Sparks area of Nevada has led to land-use changes and increased groundwater withdrawals in the valley. Population has increased from less than 800 in 1979 to more than 10,000 in 1995. The U.S. Geological Survey recently completed groundwater supply and quality studies in the valley. With increasing population, groundwater overdraft and deleterious effects on water quality may occur without careful land use planning and water supply analysis. The valley covers about 40 square miles and generally, coarse, poorly sorted alluvium derived from surrounding fault-block ranges fills the basin to depths as much as 1,000 feet. Aquifer sediments are generally finer in the north one-half and southeast portions of the basin.

Groundwater recharge occurs through water imported along Orr Ditch, which receives water from the Truckee River, and to a lesser extent from precipitation and runoff, especially around the margins of the basin. Although separated from Spanish Springs Valley by thin alluvial sediments and a north-northwest trending fault, the Dry Lakes basin to the southeast probably contributes groundwater through bedrock fractures. Water is lost to evapotranspiration, especially in the south central part of the valley, and seepage to the North Truckee Drain.

Objective – Using Groundwater Vistas and trial and error calibration, develop a steady-state groundwater model of the alluvial basin-filled portion of the Spanish Springs basin.

Information Provided -
Spatial discretization (2000 x 2000 foot cells) ( ss_start.gwv )
Observed pre-development hydraulic head map (in  ssvnv.ppt and ss427n_wt.grd SURFER format)
Constant head and top elevations along the North Truckee Drain (in ss_start.gwv)
Best-estimate spatially distributed net recharge (precipitation – evapotranspiration)
Known generalized zones of hydraulic conductivity (in ss_start.gwv)
Gridded data showing the bottom elevation of the aquifer (SS417N.DAT)
Various maps and a block diagram (ssvnv.ppt)