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..Erincipal crops are alfalfa, cotton, barley, watermelons, cantaloupes, lettuce and pasture. The crop ~alue in 1952 was $13,000,000 plus $7,500,000 for livestock. The raising of livestock is increasing in ;}1nportance. . N The reinforced concrete structure, now known as the old intake, was built in 1908, the floor ele- 'vation is 274.0. The structure was widened to eight 6-foot gates in 1917. ~he new intake structure CWith five 8-foot gates and floor elevation of 278,0 was constructed in 1945 in conjunction with the temporary rock weir. The District has 269 miles of canals and 108 miles of drains. The amount spent on construction of works by the District and its predecessors from 1908 to 1953 was approximately $5,900,000. The Colorado River Indian Reservation continues along the river for approximately 52 miles mostly in Arizona, but embraces some land in California. The reservation contains approximately 243,000 acres of which 100,000 acres of valley land in Arizona are considered irrigable. Approxi- mately 36,000 acres, in the northern part of this valley near the town of Parker, are now under irri- gation. DIVERSION: The water surface of the Colorado River at the Palo Verde Intake was of such elevation that the District could and did satisfactorily irrigate all cultivated land within approximately 90% of its gross valley area from 1908 to 1935 when the construction of Hoover Dam changed the regimen of the stream, It is also well to note that the district could and did satisfactorily irrigate during this period all cultivated land within 94.2 percent of that area considered feasible for gravity diversion. The gross area of the valley is 104,500 acres. There are 5200 acres near the intake that were never considered feasible for gravity irrigation. This area went into cultivation in 1941 and pumps from elevation 286,3. A second area of 5800 gross acres is the area which caused irrigation difficulty in 1928 to 1934; this is 5.8 percent of the gross area considered feasible for gravity irrigation. The average daily elevation of the river at Palo Verde intake from 1909 (when the gauge was established) to February 1935 (when Hoover Dam was closed was 285,9. To irrigate that por- tion of the district considered feasible for gravity irrigation (99,300 acres) requires an intake canal elevation of 286,3. However, elevation 286.3 is necessary only for 5800 acres or 5.8 percent of the area. Approximately 94.2 percent can be irrigated from an intake canal elevation of 282,3. In the 26 years from January 3, 1909 to February 1, 1935 the river was below 282.3 for only 232 days or 2.44 percent of the time, hence the Palo Verde Irrigation District feels that its obligation to- ward the cost of a solution to the diversion problem is the obligation of this 5800-acre area only, About 1927, some changes were made by the District in the river channel along the valley to improve flood protection, thereby lowering the water surface at the intake. In 1928, pumps were in- stalled on Main Canal to give a lift of less than two feet for irrigation of a 1,400-acre portion of the previously mentioned 5800-acre area in the north end of the valley. In 1931, another pump was installed at the lower end of the settling basin to pump into Duplicate Main Canal (high level). These pumps were operated until about 1934 when normal changes in the river raised the water surface so that the pumps were no longer needed. Hoover Dam was closed in February 1935. Silt carried by the river upstream from that point was impounded by the dam. The clear water from Hoover Dam exerted a scouring or degrading effect upon the bed of the stream. Engineers call this retrogression. In other words, the silt in the stream bed below the dam moves on downstream but can not be replaced by silt from upstream. This causes the stream bed to lower, thus lowering the water surface. The effect of retrogression was not immediately evident because of intervening distance (214 miles), nor was it felt following the closure of Parker Dam (59 miles upstream) in November 1938. But upon closure of Headgate Rock Dam (44 miles upstream) in March 1942 the effect was almost i=ediate. In 1943 the district in- stalled pumps within its canal system to provide water for the high lands and in 1944 Congress auth- orized construction of the temporary rock weir (First Deficiency Appropriation Act 1944, 58 Stat. 150, 157), with an appropriation of $250,000, to maintain the water surface of the river at an elevation such that the district could divert its needs by gravity. The weir was completed in June 1945, Also in 1945, the Secretary of Interior requested the Bureaus of Reclamation and Indian Af- fairs to make a survey and investigation and to submit a joint report on a permanent solution to the Palo Verde diversion problem. This report was submitted March 26,1947, and covered four pos- sible plans: