One swallow does not make a summer. Nor does one dry month or two in the California winter presage a drought. But even if snowfall in the mountains reaches normal levels during the next six weeks, 1987 will be officially known as a critically dry year. This could lead to cutbacks of normal irrigation-water deliveries to farm customers of the state Water Project. Many farmers then would pump more water from their Central Valley aquifers, which already are overdrafted.
Fortunately, reservoirs serving California are relatively full because of holdover storage water from the previous wet years. Lake Mead on the Colorado River is at 122% of average; Lake Shasta, in the federal Central Valley Project, is at 94%, and Lake Oroville, the keystone of the state Water Project, has 104% of its average storage.
As skiers know, snowfall has been far below normal in the Sierra, ranging down to 31% in the Tulare River watershed as of Feb. 1. Particularly vulnerable is the City of Los Angeles, which normally gets 75% of its supplies from eastern Sierra runoff into the Owens River system. Even with the recent storms, Owens River Valley runoff is expected to be less than half the normal amount. The city's vulnerability stems from the fact that it has very little reservoir storage available in the Owens Valley.
However, the city can call on the Metropolitan Water District for additional Colorado River supplies this year. Even with Arizona now taking a portion of its Colorado River entitlement, there is surplus water in the Colorado system with its giant reservoirs at Lake Mead and Lake Powell in Glen Canyon.
The real pinch would come if the state suffers two or more dry years in a row, as in the last major drought a decade ago. The Colorado River is not likely to yield such massive surpluses of water for years to come, if ever, and cannot be counted on much longer for the backup supplies so comfortably available now. Environmental constraints on the pumping of state water from the Sacramento-San Joaquin Delta become even more severe in dry years, thus limiting exports to the south.
State and regional water managers have planned and launched a number of innovative programs for storing surplus water during bountiful years in underground basins for use during dry years. But there is not yet enough water in these storage banks to be of significant help now.
The lesson is that California never knows when a drought may be just around the corner. MWD and the state should push ahead with their storage programs on an urgent basis. And the entire state needs to put aside for all time its relatively relaxed approach to water conservation. Californians demonstrated in 1976-77 how much water they can save without inconvenience. If California is to be assured of ample water supplies in the future, the novelty of drought-year conservation practices will have to become everyday habit.