Environmental impacts of groundwater overdraft:: selected case studies in the southwestern United States

The southwestern United States - this paper's study region - is home to large urban centers and features a thriving agro-industrial economic sector. This region is also one of the driest in North America, with highly variable seasonal and inter-annual precipitation regimes and frequent droughts. The combination of a large demand for usable water and semi-arid climate has led to groundwater overdraft in many important aquifers of the region. Groundwater overdraft develops when long-term groundwater extraction exceeds aquifer recharge, producing declining trends in aquifer storage and hydraulic head. In conjunction with overdraft, declines in surface-water levels and streamflow, reduction or elimination of vegetation, land subsidence, and seawater intrusion are well documented in many aquifers of the southwestern United States. This work reviews case studies of groundwater overdraft in this region, focusing on its causes, consequences, and remedial methods applied to counter it.