California Drought Early Warning System

Conditions for the week of Jan. 4-10

With more than two inches of precipitation falling from southwestern Washington southward to Los Angeles, CA, including over a foot along the northern and central California coast and on the Sierra Nevada range, significant increases were made to the capacity of the state’s major reservoirs. Most were above the normal Jan. 10 historic levels and still filling, with most USGS-monitored streams at near or at record high flows. The state’s Sierra snow water content (SWC) was also well above its Jan. 10 normal, with a state average of 16.2”, or 135% of normal. The Northern Sierra, San Joaquin, and Tulare basin station precipitation indices all exceeded their wettest year (1982-83; 1968-69 for Tulare) as of January 10 with 41.9 (203%), 30.8” (199%), and 20.0 (190%) inches, respectively. In fact, the Northern Sierra index gained 13.2 inches since Jan. 1, or 26% of its ANNUAL average in 10 days. Oroville Reservoir started the New Year with a deficit in its conservation pool of 750,000 acre-feet, but has gained 350,000 acre-feet or more. Since northern portions of California also benefited from a decent Water Year (WY – Oct. 1 through Sept. 30) last year, one- to two-category improvements were made. In contrast, with long-term drought impacts more severe and widespread in southern sections, only a one-category improvement was made to most areas since above-ground (reservoirs) and underground (wells) water supplies still lagged below normal. And in southern Santa Barbara, Ventura, southern Kern, and northwestern Los Angeles counties, exceptional drought (D4) remained intact as the WY has been below normal so far, while hydrologic impacts lingered.

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