Drainage Area: 17,000 square miles
Size: 15% of the total area of Nevada
The Humboldt River Basin (HRB) is the only major river basin that is entirely within the State of Nevada. Precipitation supplies all the water that enters the basin; consequently, the variability in climate has significant impacts on the hydrology of the area. In addition, increased development which has been superimposed on natural climate fluctuations affects the water resources of the basin. Continued groundwater withdrawals within the Humboldt River Basin are likely contributing to streamflow depletion of the Humboldt River. The timing and magnitude of the effects of groundwater withdrawals on streamflow of the Humboldt River are not well understood. Although groundwater use in the Humboldt River Basin is primarily for agriculture, a substantial quantity of groundwater has been removed from consolidated rock units and basin fill as part of mining activity in the middle Humboldt River basin. The contribution to streamflow depletion by mine dewatering is currently thought to be relatively small, largely because much of the water was or continues to be returned to the river or to unconsolidated deposits near the river. However, many Humboldt River water rights holders contend that mine dewatering contributes significantly to streamflow depletion.
To evaluate the impacts of groundwater withdrawals on streamflow, three transient, regional-scale flow models will be developed and documented. The three models will represent the upper, middle, and lower Humboldt River Basins, respectively. The middle HRB model will be developed by the USGS; the upper HRB model is being developed separately and simultaneously by the Desert Research Institute (DRI); and the lower HRB model will be co-developed by the USGS and DRI. These models will assist us in:
These estimates will provide the Nevada State Engineer with appropriate information to understand and evaluate the potential effects of groundwater withdrawals on the Humboldt River in order to make informed decisions regarding conjunctive use and possible augmentation of flow to senior water right holders. In addition, this work will provide the State of Nevada an opportunity to inform stakeholders within the Humboldt River Basin about processes related to the interaction between groundwater and surface water.