AZ vs. CA:10 California Exhibits, Vol. X; Nos. 458-528

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system of reservoirs to catch and hold the large periodic floods which occur approximately at intervals of 10 years. The net safe yield of the presently constructed system is 31.9 millions of gallons per day, while the average use in 1942 was 36.24 millions of gallons per day, and in 1943, 42.19 millions of gallons per day, and the estimated use in 1944 is 46.16 millions of gallons per day. Increased storage facilities are contemplated by the city, but even if completed in the near future, no assumption of an augmented firm supply can be made-for, if a cycle of dry years, similar to the driest cycle of record, should recur, there would be little run-off to store. The annual rainfall averages about 10 inches along the coast and is 4 to 5 times greater near the crest of the mountain ranges. Practically all of the precipitation occurs during the months of December to April, inclusive. The rainfall varies from year to year, and the volume of the annual run-off is very erratic, ranging from extremes of only 2.6 to as much as 580.8 percent of the mean for the 60-year period of record, 1883 to 1943. Because of wide variations from year to year in stream run-off, a safe yield from local sources must be predicted on holdover storage with which to enter dry cycles. Local storage developments might not provide additional water likely to be needed for this purpose, as demonstrated by the history of San Vicente Reservoir, which was completed 2 years ago and is only 12 percent full now. In the light of past records of run-off from the local streams, there is cause for anxiety regarding the ability of the supply as developed by present works to meet the demand which is now being made upon it. Fortunately, good run-off filled the reservoirs in the winters 1940-41, 1941-42, 1942-43, and 1943-44. In June 1944, it was