Managed Aquifer Recharge (MAR) and Design and Construction of Hydraulic Barriers against Seawater Intrusion: the California Case

Managed aquifer recharge (MAR) has been practiced in California for over a century, using a range of artificial recharge methods, including surface spreading basins, injection wells and aquifer storage and recovery (ASR) wells. Intense municipal and industrial development of coastal regions, particularly in southern California, during and following World War II, led to overdraft of coastal groundwater basins, where groundwater levels were drawn down below sea level, resulting in seawater intrusion into freshwater aquifers. Surface water is imported from the Colorado River and later northern California to satisfy water demands of a growing population. This imported water is also a water supply used for injection into to injection wells constructed in the 1960s along the coastline to repel seawater from intruding into coastal aquifers. Since the 1960s, these seawater intrusion barriers have evolved in terms of water supplied for injection and in their construction and operation details. Imported water supplies are being completely replaced with highly treated wastewater and the injection wells are being constructed so that they are more automated to reduce operational costs. The West Coast Basin of southern California is provided as a case study of the evolution of hydraulic barriers used for protection against seawater intrusion into coastal aquifers. (Author)