Assessment of Total Dissolved Solids and Nutrient Inputs from Nonpoint Groundwater Discharge in the Lower Truckee River Basin, Nevada

Long-term water quality monitoring in the lower Truckee River Basin, Nevada, indicates significant increases in most solutes (major ions and nutrients) during periods of low flow. Simple solute budgets for the area suggest that much, if not all, of these increases are due to non-point groundwater inputs derived from natural (e.g., geothermal) and anthropogenic (e.g., agricultural) sources. Total dissolved solids loadings over a 20-km reach may exceed 6,000 kg/d, or approximately 10% of the amount permitted at municipal wastewater treatment facilities upstream. Currently, agricultural water rights are being purchased in the study area, with the partial expectation that a reduction in flood irrigated field crops may result in an associated reduction in non-point groundwater returns, creating opportunities for obtaining pollution credits upstream. Ongoing studies, described here, are designed to characterize the relationship between land-use activities, non-point groundwater returns to the river, and potential impacts to instream biotic communities.