San Joaquin Runoff Total Pulls A Season-Concluding Surprise
There is no surprise that the central and southern San Joaquin Valley are winding up a second consecutive below-average water year but the San Joaquin River’s total 2012-13 runoff is startling.
Despite months of mostly dry weather, the San Joaquin River’s calculated full natural runoff has already topped what occurred in 2011-12, even though nearly two weeks remained (at press time) before this very dry water year is to conclude September 30
As of September 16, San Joaquin River runoff for 2012-13 stood at 854,682 acre-feet, just under 47% of average. The entire 2011-12 water year produced 831,000 acre-feet of natural runoff, 45% of average. Natural flow figures are calculated based upon changes in reservoir storage and reflect how much water would have been flowing in the river at Friant if there were no dams.
The San Joaquin’s increased water year total is the result of the water year’s only really productive storms, all of which occurred before New Year’s.
DRY WINTER AND SPRING
From January into early spring, precipitation across the valley and southern Sierra established dubious records for the least precipitation ever recorded during what statistically should be the wettest time of year.
Friant water users rely upon the San Joaquin River for their Central Valley Project water diverted at Friant Dam into the Madera and Friant-Kern canals.
Friant’s CVP water supply remains at 62% for Class 1 users. Last year’s Class 1 water supply declaration ended up at 57%. No Class 2 water has been available over the past two years. The U.S. Bureau of Reclamation’s new contract supply year will begin March 1.
Millerton Lake storage on September 16 remained surprisingly high at 302,159 acre-feet, 58.1% of capacity.
Irrigation deliveries continue with just over 700 cubic feet per second in the Friant-Kern Canal and 289 c.f.s. being released into the Madera Canal. The San Joaquin River release was 350 c.f.s. for downstream riparian pumpers and San Joaquin River Restoration Program interim flows.
Reclamation reported September 16 that actual Millerton Lake inflow was 1,482 c.f.s. although the calculated natural flow at Friant was zero.