The history of irrigation as an organized agricultural practice predates the earliest written histories and is best gleaned from the archeological evidence to be found in the various arid and semiarid regions of the world. The history of man's continuing struggle to master the hydrological cycle to the benefit of agriculture has been well reviewed in a volume by D. Hillel. In 1938, a series of federal laboratories to conduct agricultural research on important regional problems was authorized by Congress. A new dimension to the problems of irrigated agriculture was added in 1982. The costs of providing for agricultural drainage from irrigation projects had been minimized in project documents and has often been underestimated in cost benefit analysis. The future of irrigated agriculture depends upon many factors. Farmers can manage their irrigation water more effectively and thereby reduce the contaminants that leave the soil profile through leaching.