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RESTORING OUR GROUND WATER By COLONEL NORMAN E. PEHRSON District Engineer Corps of Engineers, Los Angeles Mr. President, members of the Colorado River Water Users Association, and guests: It is an honor and a pleasure to meet with you today. Meetings such as this have great value. The exchange of information, the expression of views, often widely divergent, and reports by various experts on particular facets of water resources development all serve to broaden our individual know- ledge of a complex field. The communication of ideas and experience that goes on during meetings such as this leads ultimately to improved measures for protecting and improving water and related land resources, to the mutual benefit of everyone concerned. Today I will speak to you briefly on the role of the Corps of Engineers in the wise use and management of our ground water resources. Basically, our philosophy regarding the conservation of these resources is to bury floodwaters whenever possible. Although ground water represents the larg- est source of fresh water available on the earth - far greater than all the water in lakes, reservoirs, and streams - ground water, or rather the lack of it, has posed many problems in most of the arid South- west, especially in the more highly developed areas. Overi-ithdrawal, contamination, and years of drought have periled this important resource. For many years, it has been obvious that the burgeoning populations of the metropolitan areas of the Southwest and the limited supply of water in: the region were on a collision course unless drastic actions were taken to utilize the underground reservoirs generously provided by nature. As a result, we have worked closely with local flood control districts, water agencies, and water companies to insure that the design and operation of our flood control works provide both optimum flood con- trol and water conservation. I will describe briefly what we have done thus far and what we expect to do in the future towards turning floodwaters from a natural menace into a national asset. A successful example of the maximum utilization of floodwaters is what has been done in con- nection with the Los Angeles County Drainage Area Projedt, which is now nearing completion. Known as LACDA, the project comprises an intricate system of channels, dams, and debris basins with 95 miles of main-stream channel, 190 miles of tributary c~annel, 5 dams, and 22 debris basins. Ever since pueblo days, the City of Los Angeles and nearby cities and towns have depended on the under- ground basin for a large part of their water supply. Origina)ly, in Los Angeles County as elsewhere, the natural channels and the flood plains were the primary ~ources of ground water recharge. However, many flood plains in Los Angeles County were swallowe~ up in urban development, and the need to confine floodflows to formal channels became markedly 'evident in the 30's when disastrous floods destroyed property worth millions of dollars and took rriany lives. Federal assistance was needed to aid the County in its fight against floods. In 1935, Emerg~ncy Relief Administration funds were made available with the proviso that the work be done under the direction of the Army Engineers. This was the first step in Federal participation in the LACDA project - the successful joint venture of the Corps and the Los Angeles County Flood Control District. In general, the Corps has constructed major res- ervoirs and channels, and the County has provided rights-of-way and has maintained and operated the channels. The Corps operates and maintains the reservoirs in close cooperation with the County. Dur- ing storms, both agencies work round-the-clock, commun\cating by direct telephone line and teletype. As the County calls for releases that its spreading ground,S can handle, the Corps' damtenders operate the gates to provide the required releases. No water is wasted unless a major storm reaches propor- tions that demand flood control operation only. At the start of our studies for the LACDA project, it became obvious that no simple solution would suffice for this area, whose ground water supply was its lifeline and whose vulnerability to flood damage required structurally stable paved channels that would carry floodwaters across the . . -10-