I. INTRODUCTORY MATERIAL

The Yuma study area is located in the extreme southwest corner of Arizona (Figure I-i). The city of Yuma has a long and colorful history because it was a stopping-off point on the southern route to Calfornia. Interstate Highway 80 and the Southern Pacific Railroad use the Yuma crossing to connect both traffic and commerce from southern California with that which comes from Phoenix and Tucson. Yuma is part of a very arid region in the southwest; yet farming is the single most important industry. This is due to the rich soil found in the Gila and Colorado River flood plains and ~he extensive use of irrigation waters. B. Local Support Contacts with local farmers, civic leaders and government representatives wer made during the field season. Access to information, both public and private, was obtained. Special thanks should be extended to the U.S. Geological Survey, Yuma, Arizona, and Menlo Park, California; Bureau of Reclamation