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<br />- <br />O",,,,,,~'l! <br />[: u ':'.'v .~ ,. ~ ~ <br /> <br />comparable in severity. Continuation of the present drought through 1991 could <br />well constitute a "critical period" for the operation of the Central Valley Project <br />more severe than those used to determine the yield and other capabilities of the <br />pioj ect. <br /> <br />According to the indices of drought, measurements of soil moisture indicated very <br />moist to mild drought to extreme drought conditions at the beginning of the 1990 <br />water year, Conditions degraded as the water year progressed, and, by the end of <br />the water year, conditions had degraded to an extreme drought situation for two- <br />thirds of the region and moderate to severe drought for the remainder, Overall, <br />soil moisture was much drier at the beginning of water year 1991 (September 30, <br />1990) than at the beginning of the previous water year (September 30, 1989.) <br /> <br />Snowpack in the tributary basins to the Central Valley in California was well <br />below normal on February I, 1990, By May 1, conditions had degraded to below <br />50 percent of normal in all basins, Consequently, accumulated inflow to the <br />region's reservoirs was below normal to well below normal throughout the year, <br />Some improvement and degradation were alternatively felt in various areas, but <br />the year ended under similar circumstances to those at the beginning, Many <br />areas had less than 50 percent of inflow for the year. <br /> <br />At the beginning of the 1990 water year, reservoir storage ranged from well below <br />nonnal to near normal in the Central Valley of California and in the Klamath <br />River basin in Oregon and California, Basins in southern California and in <br />Nevada were, for the most part, well below normal at that time, Conditions <br />degraded over the region through the water year and generally were well below <br />nonnal throughout, except in the San Joaquin River basin where storage was near <br />nonnal by year's end on September 30, 1990. <br /> <br />In Nevada, the Lahontan Project experienced water shortage conditions during <br />1990. In March, the Truckee-Carson Irrigation District set the Newlands Project <br />water allocation at 65 percent of entitlement, but later revised the allocation to <br />70 percent due to rainfall during ApriL The Pershing County Water Conservation <br />District initially set the Humboldt Project water allocations at 25 percent of <br />entitlement but later adjusted the allocation to 27,5 percent, due to April <br />precipitation, The water surface level of Lake Tahoe fell below its natural rim <br />outlet to the Truckee River on September 14, resulting in conservation measures <br />along the Truckee River, This is only the eleventh time since 1990 that the lake <br />level has dropped so low, <br /> <br />Projected Conditions for 1991 <br /> <br />Early analyses of water supply possibilities for 1991 indicate that full deliveries <br />for Central Valley Project contractors will probably require normal or greater than <br />normal runoffin 1991. The distribution of runoff throughout the project will have <br />a bearing on water delivery capabilities because of the varying refill potential and <br /> <br />6 <br />