Never in nearly a century of Department of Water Resources (DWR) recordkeeping has so much precipitation fallen in the northern Sierra in a water year. DWR reported today that 89.7 inches of precipitation – rain and snowmelt – has been recorded by the eight weather stations it has monitored continuously since 1920 from Shasta Lake to the American River basin. Today’s total surpassed the previous record of 88.5 inches recorded in the entirety of Water Year 1983. The region’s annual average is 50 inches.

California traditionally receives 30 to 50 percent of its annual precipitation from atmospheric rivers (ARs), long and relatively narrow “rivers in the sky” laden with moisture that blow in from the Pacific. The West Coast experienced 46 ARs between October 1 and March 31, the first six months of Water Year 2017. Nearly one-third of the total were “strong” (13) or “extreme” (3) ARs.

DWR’s 5-station San Joaquin index is keeping pace with Water Year 1983’s record total of 77.4 inches in the region. Today’s total of 68.2 inches among the stations is 194 percent of the average precipitation recorded by today’s date during the water year and far exceeds the San Joaquin annual average of 40.8 inches.

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