Sierra snowpack is below average. What it means for water users in Stanislaus County
After a slow start, Modesto’s rain now exceeds the average, but snow in its mountain watershed continues to lag.
The Modesto Irrigation District has recorded 7.45 inches of rain at its downtown office as of 10 a.m. Thursday. Its water year starts July 1, but the storms happen mainly from November through March.
MID has a historical average of 6.79 inches of rain by this point in winter. An average year brings a total of 12.17 inches.
MID and nearby water suppliers rely mainly on the central Sierra Nevada snowpack. It was 52% of average as of Thursday, the California Department of Water Resources reported.
The good news? Water stored in reservoirs is well above average, thanks to last winter’s massive storms. That could mean no major cutbacks for many cities and farms as demand peaks from spring to fall.
The recent storms have been warmer than average, State Climatologist Michael Anderson said in a DWR news release. That means less snow than a year ago, “once again demonstrating how California can swing from one extreme to another,” he said.
Water rights vary around Valley and state
In any year, the water outlook varies for suppliers around the state based on river rights and access to reservoirs.
MID and the Turlock Irrigation District have senior rights to the Tuolumne River and own one of the state’s largest reservoirs, Don Pedro. It was at 81% of capacity as of Thursday and at 115% of average for this time of year.
That carryover from last year would help MID and TID meet demand even if the rest of winter is drier. The districts irrigate large farmland expanses and supplement groundwater tapped by residents of Modesto, Ceres and Turlock.
On the Stanislaus River, storage in New Melones Reservoir was at 83% of capacity as of Thursday. It held 143% of the average water for this time of year. The senior rights are held by the Oakdale and South San Joaquin irrigation districts. The latter also provides part of the drinking water for Escalon, Lathrop, Manteca and Tracy.
It usually takes multiple below-average years to trigger cutbacks in MID, TID, OID and SSJID. Even then, most of the water continues to flow thanks to the sheer size of Don Pedro and New Melones.
West Side water can fluctuate more
Water is trickier for the West Side of Stanislaus County, which is supplied mainly by federal water pumped from the Sacramento-San Joaquin Delta.
The contracts for many districts can mean zero water from the Central Valley Project during droughts. It can be reduced even in somewhat wetter times to protect fish from the delta pumps.
Four districts get most of their water even in drier years because of a 1930s agreement preceding the CVP’s construction. They gave up their rights to direct use of the San Joaquin River in exchange for priority in the federal contracts. The largest is the Central California Irrigation District.
The CVP has not yet announced its water allocations for 2024. The initial estimate is made in February and can increase if March brings above-average storms.
This winter has brought El Niño, a warming of Pacific Ocean water near the equator that can send storms to California. DWR Director Karla Nemeth noted that it has had only modest impact so far.
“Californians must prepare for all possible conditions during the remaining months of the rainy season,” she said.
