The alluvial basins in the Southwestern United States constitute a major source of ground water and are relied upon extensively for agricultural, industrial, and public water supplies. Large-scale depletion of ground water is directly related to pumping that has occurred in the past few decades and is continuing today. The U.S. Geological Survey has started a 4-year study of the alluvial basins in south-central Arizona and parts of California, Nevada, and New Mexico. The study is designed to document and describe the hydrologic setting in the basins, the ground-water resources available, and the effects of historical development on the ground-water system. To aid in the study, mathematical models of selected basins will be developed for appraising the local and regional flow systems.
Major tasks necessary to accomplish the study objectives include accumulating existing data on ground-water quantity and quality, entering the data into a computer file, identifying data deficiencies, and developing a program to remedy the deficiencies by collection of additional data. The approach to the study will be to develop and calibrate models of selected basins for which sufficient data exist and then to develop interpretation-transfer techniques whereby general predevelopment and postdevelopment conceptual models of the hydrologic system in other basins may be synthesized. The results will be applied to selected basins for testing, calibration, and modification. The end result of the project will be a better definition of the hydrologic parameters and a better understanding of the workings of the hydrologic system in the alluvial basins. The results will include models that can be used to study the effects of management alternatives and water-resources development on the hydrologic system.
