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.