Task 2 — Recharge and Discharge
Regionally consistent estimates of mean annual recharge and discharge, including discharge by evapotranspiration (ET), pumpage, streamflow, and springflow will be developed. Preliminary estimates for discharge and recharge will be developed using available data; estimates will be updated, where possible, with new data acquired during this study. The mean annual estimates of recharge and discharge will be developed using the following:
Spatially-distributed estimates of mean annual recharge will be developed using a two-step approach:
Spatially-distributed estimates of mean annual discharge will be developed by quantifying streamflow, springflow, pumpage and ground-water ET. Mean annual precipitation over discharge areas will be estimated and the source of streamflow into or out of major discharge areas will be determined. This data will be used to help partition phreatophyte ET rates into ground-water or surface-water components. Determining reasonably accurate estimates of mean annual discharge will include the following:
Springflow — Available springflow measurements will be compiled and field checked including characterization of channel and stream-source waters. Abiotic and biotic characteristics of approximately 60 springs will be quantified to develop a model relating discharge sources.
Pumpage — Current pumpage will be estimated using all available pumpage data from the State of Nevada Ground-Water Pumpage Inventories. For basins not inventoried, large irrigation use will be estimated from irrigated acreage delineated using remotely-sensed satellite data, estimated crop application rates, and any associated information from State well log and water-use permit databases.
For more information on this study, please contact:
USGS Nevada Water Science Center