USGS Home
Contact USGS
Search USGS

U.S. GEOLOGICAL SURVEY
Scientific Investigations Report 2007–5205

Back to Table of Contents

Ground-Water Inflow Simulated from Watershed Models Compared with Previous Estimates

Ground-water inflow and ephemeral runoff simulated using the watershed models of the Carson Range and Pine Nut Mountains were combined with previous estimates of ground-water inflow to the northern part of Carson Valley, and ground-water recharge from precipitation on the western alluvial fans and eolian sand and gravel deposits made by Maurer and Berger (2007), for comparison with the previous estimates of ground-water inflow. The estimates for ground-water inflow and runoff from ephemeral watersheds of the Carson Range using index models selected on the basis of bedrock type, as described above, were used in calculating the totals.

Mean annual ground-water inflow to the basin-fill deposits of Carson Valley from the Carson Range simulated from the ephemeral and perennial watersheds totals 20,000 acre-ft. The volume of 20,000 acre-ft is 7,000 acre-ft less than the estimate obtained from the chloride-balance method and almost double the estimate from the water-yield method (table 8). Inflow simulated from the Pine Nut Mountains and the eastern alluvial fans was 16,000 acre-ft, which is almost 50 percent greater than the 11,000 acre-ft estimated from the chloride-balance method. For both the Carson Range and the Pine Nut Mountains, the estimates of ground-water inflow simulated from the watershed models were considerably greater than the estimate obtained using the water-yield method. This is in part because the models simulated greater volumes of ground-water inflow from the perennial watersheds, and in part because the models indicate that ground-water inflow does take place from the ephemeral watersheds, which was assumed to be negligible by Maurer and Berger (2007, p. 31).

Maurer and others (2007, p. 28) used soil-chloride data to determine that ground-water recharge from precipitation was not taking place on the eastern side of Carson Valley. However, the soil-chloride data were collected only near the tops of hills in the area of ephemeral runoff, and not in ephemeral stream channels. The soil-chloride data and watershed modeling results suggest ground-water inflow estimated from watershed 11e likely is derived from infiltration of runoff beneath ephemeral stream channels.

The total mean annual ground-water inflow simulated from the watershed models for Carson Valley was 38,000 acre-ft, similar to the volume obtained from the chloride-balance method, 40,000 acre-ft.

Back to Table of Contents