Geohydrology and Simulated Response to Ground-Water Pumpage in Carson Valley, A River-Dominated Basin in Douglas County, Nevada, and Alpine County, California

This investigation of the ground-water hydrology in Carson Valley was conducted from 1980 through 1985 by the U.S. Geological Survey, in cooperation with Douglas County. The purpose of the study was to:

(1) collect, compile, and analyze hydrologic data to quantify the hydrology of the valley and to enhance the understanding of the valley’s geohydrologic system; and

(2) develop a ground-water model that would simulate the response of the hydrologic system to applied stresses and that could be used to estimate the probable hydrologic effects of various development alternatives.

This report presents the results of the investigation.

Work began with a gravity survey in 1980 to determine the depth to bedrock in Carson Valley; the results are discussed in detail in a separate publication (Maurer, 1986). From 1981 to 1983, work included:

(1) measurement of water-level fluctuations and surface-water runoff,

(2) drilling of additional observation wells,

(3) collection of ground-water pumpage data and measurement of pump efficiencies, and

(4) compilation of existing data reports and drillers 1 logs to obtain estimates of geohydrologic characteristics of the ground-water reservoir.

Development of a water budget and initial estimates of hydraulic conductivities and specific yield were accomplished in 1983. From 1983 to 1985, the ground-water model was developed and calibrated, and simulations of possible ground-water development were made. The model, which represents a compilation of all available data, was used to

(1) test estimates of the geohydrologic characteristics of the ground-water reservoir,

(2) evaluate the components of the water budget for the basin,

(3) enhance the understanding of the hydrologic flow system in the basin, and

(4) simulate the effect of various possible developmental alternatives on Carson River outflow, evapotranspiration, ground-water levels, and ground-water storage in the valley.