Safe yield of large and small aquifers in agricultural regions
University of California
Picture Not Available
The safe yield is perhaps the most important management variable of an aquifer: it describes the maximum amount of groundwater that can be extracted from an aquifer without causing adverse effects. This paper compares four traditional methods and one novel method to estimate the safe yield in aquifers supporing agriculture. The paper also stresses the importance of adjusting groundwater extraction to protracted decline in recharge caused by drought. This is essential to protect against adverse impacts such as seawater intrusion in coastal aquifers and against land subsidence in layered aquifers with compresible aquitards. Two examples are presented illustrating this paper's methodology. One involves a 15 square mile aquifer supporting agriculture in the Carpinteria Valley, Santa Barbara, County. The other example concerns the 15000 square mile regional Edwards aquifer in south central Texas, which serves agricultural, aquatic, and urban functions. Both aquifers have detailed water-balance data for nearly one century, providing strong statistical reliability for the estimates of safe yield.