Control of Sea‐Water Intrusion in a Ground‐Water Aquifer a

Sea‐water intrusion into ground‐water reservoirs occurs when permeable formations outcrop into a body of sea water and when there is a landward gradient. Intrusion can be controlled by reducing pumping, by increasing supply, or by forming some type of barrier. A pressure barrier has been operated in Los Angeles County, California. Special facilities are needed. Costs of operation are high. The intrusion of sea water into ground‐water reservoirs can greatly impair the water‐supply systems of local areas adjacent to coastlines and tidal estuaries. Such intrusion is always the result of some activity of man either in trying to improve his environment or in his use of natural resources. Following is a discussion of how intrusion occurs, some ways of controlling intrusion, the results of one project in southern California where intrusion is being controlled, and some examples of related costs.