Groundwater residence time estimates obscured by anthropogenic carbonate.

Groundwater is an important source of drinking and irrigation water. Dating groundwater informs its vulnerability to contamination and aids in calibrating flow models. Here, we report measurements of multiple age tracers (C, H, Ar, and Kr) and parameters relevant to dissolved inorganic carbon (DIC) from 17 wells in California's San Joaquin Valley (SJV), an agricultural region that is heavily reliant on groundwater.