California's Central Valley Groundwater Wells Run Dry During Recent Drought

Abstract

Declining water tables are causing wells to run dry in California, but the prevalence and spatial distribution of wells that have run dry are not known beyond anecdotal and voluntary reports. Here, we apply a new, simple, and measurement-driven method to calculate a localized water table; we show, for the first time using observations, that up to one-in-five wells now runs dry in California's Central Valley. The spatial distribution of wells identified as having dried up replicates hot spots of wells identified as having run dry in a voluntary reporting system, while also capturing impacts on groundwater wells that have not reportedly run dry. We assess the rates of drilling throughout the Central Valley and find, surprisingly, that domestic wells are being drilled deeper at a rate that exceeds agricultural wells across much of the central Central Valley. Because new groundwater wells are costly (i.e., $10,000 to $100,000), we suggest explicitly considering dry wells in groundwater sustainability planning to protect homes and farms from the loss of access to reliable water supplies in the future.