Aqueous Geochemistry of Surface Water and Groundwater from Domestic Supply Wells in Fractured Rock, Nevada County, CA

Approximately 4% (1.6 million) of California residents depend on groundwater for domestic use (USGS Water Use Data for California, 2018). In Nevada County, CA, located in the foothills of the Sierra Nevada Mountains, a higher proportion of residents (75%) rely on groundwater for domestic use (Nevada Irrigation District, 2018; US Census Bureau, 2017). Between 2010 and 2015, domestic groundwater use increased 25% (USGS Water Use Data for California, 2018). Sources and pathways of recharge water to domestic wells must be better understood to determine how vulnerable this rural population may be to climate change. To this end, 56 surface and groundwater samples were collected from two watersheds in western Nevada County during 2010-2011 and analyzed for stable isotopes of water (δ18O and δD) and major ions (bicarbonate, calcium, chloride, magnesium, potassium, sodium, and sulfate).