Atmospheric Rivers Pushed Total to 89.7 Inches since October 1
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.
The six-station index in the Tulare Basin, often called ground zero of California’s five-year drought, which officially ended in most of California on April 7, has recorded 178 percent of the amount of precipitation that normally falls by this date during an average water year. Total precipitation so far is 45 inches, about 1.5 times the average annual precipitation of 29.3 inches in the basin.
The snow water equivalent of California’s snowpack is far above average throughout the Sierra Nevada — 176 percent of the April 13 average. DWR will conduct its final snow survey of the season on May 1 at Phillips Station in the Sierra 90 miles east of Sacramento.