Water flows into the American River were increased Tuesday, despite the ongoing drought, because state and federal officials are fighting to keep salinity from San Francisco Bay from intruding into the Sacramento-San Joaquin Delta.
The U.S. Bureau of Reclamation boosted water releases from Nimbus Dam into the American River from 2,000 to 2,500 cubic feet per second. This follows other increases in late May for the same reason.
Due to the drought and very low snowmelt, there simply isn’t enough natural runoff from the Sierra Nevada to keep salinity out of the Delta. Controlling salinity is essential because the Delta provides fresh water to 23 million Californians and 3 million acres of farmland.
Although water deliveries from the Delta have been reduced to historic lows because of drought, officials want to keep salinity out of the Delta because, once it intrudes, the salty water can take weeks or months to flush out. As the summer wears on, sufficient water for that task in upstream reservoirs could run out.
Under state law, salinity also must be controlled to protect water quality for users who divert directly from the Delta. This includes farmers on Delta islands as well several urban water consumers.
The additional water release into the American River on Tuesday was triggered because of unusually high tides forecast in coming days, which will increase the odds of salinity intrusion.
“We expect these high tides for the next week to 10 days,” said Janet Sierzputowski, a Reclamation spokeswoman. “So whether we’ll see the 2,500 go higher or not, it’s hard to say at this point.”
Reclamation is coordinating with the California Department of Water Resources to jointly deal with the salinity problem. Late last week, DWR increased water releases from Oroville Reservoir on the Feather River. On Wednesday, Reclamation plans to increase releases from Keswick Reservoir on the Sacramento River.
The additional water is not being diverted from the Delta to serve DWR and Reclamation water users elsewhere. Instead, the water is being allowed to flow toward San Francisco Bay and the ocean to control salinity. Delta diversions have remained steady at just 375 cfs for weeks, all of it diverted by DWR’s facilities, which primarily serve urban customers.