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I I I I I I I I I I I I I I I I I I I 3695 PALO VERDE IRRIGATION DISTRICT UNIT - CALIFORNIA The Palo Verde Irrigation District (PUDI) is located around Blythe, California, between Parker Dam and Imperial Dam. It extends fOr approximately 30 miles below its diversion point and is about 10 miles wide at its widest location. The PUDI has about 92,000 acres of irrigated land with approximately 32% of this land having a multiple cropping opera- tion. It has over 290 miles of canals and laterals for water delivery and a 150-mile system of open drains. The PUID has an unlimited water right to irrigate a gross acreage of 104,500 acres. It annually diverts an average of about 915,000 acre-feet and discharges as return flow about 450,000 acre-feet annually. The salt discharge from the drainage system was estimated at 1,097,000 tons in 1974. The net salt increase from diversion to discharge was estimated at 152,000 tons. The majority (144,000 tons) of this increase was found to be coming from the Palo Verdes subarea in the southwestern portion of the District. This sub- area is approximately 11, miles long and has a maximum width of about 3, miles, and contains a gross area of about 12,550 acres. The main plan for reducing the salt leading from this subarea would involve the implementation of an irrigation efficiency pro- gram and lining about 20 miles of laterals. Currently, the present on-farm efficiency in this subarea is about 42 percent, and it was felt that this could be increased to 60% with the construction of some on-farm improvements. The increase in efficiency and lateral improvemants would decrease the salt concentration at Imperial Dam by about 7.9 mg/L at an annual equivalent cost of $255,000 mg/L (July, '81). This program would result in a net decrease of 88,600 tons of salt being annually discharged to the Colorado River. Since the District has an unlimited water supply, there is little incentive to attain a greater irrigation efficiency. How- ever, the reduction of water use can result in labor and fertilizer' savings and in some instances increase crop yield. In these ways the cost of an irrigation management program could be recouped. The WPRS did have a demonstration program in effect in the PUID from 1973 to 1977, but at the request of the District it was discontinued. It appears that the irrigators in the District are not sufficiently interested in an irrigation management program without considerable federal incentive. ' More detailed studies, including ground water modeling, are required to verify a potential for a salinity control project and to provide a basis for initiating a Federal expenditure program. Detailed studies could be completed by 1985, and with timely Con- gressional authorization, construction could begin in 1989. (updated 11/12/81) DS:cs -28-