The state Department of Water Resources is rushing to place temporary dams in three channels in the Sacramento-San Joaquin River Delta to hold back the intrusion of seawater from San Francisco Bay and protect water quality during this drought year.
With less fresh water than normal flowing through the rivers, salty seawater is creeping into the Delta, which provides drinking water for 25 million people -- including 1.8 million customers of the Santa Clara Valley Water District, 500,000 in the Contra Costa Water District, and 19 million people served by Southern California's Metropolitan Water District -- and 3 million acres of farmland. The $25 million barriers would prevent the river water from flowing out to tributaries and instead push it downstream to where giant pipes capture the supply.
"The idea is that we will be able to avoid having to release water from reservoirs to meet water quality, and conserving as much as we can for later," said Mark Holderman, the project manager with the state water department.
The barrier idea -- last used during the state's drought of 1976-77 -- was mentioned by Gov. Jerry Brown in January when he declared a state of emergency. 2013 was the driest year on record.
Diverting the natural flow of the waterways will have an impact on wildlife and recreation in the Delta.
Maria Rea, Sacramento-area supervisor at the National Marine Fisheries Service, said north Delta barriers would block the migration paths of the chinook salmon, but may be a necessary evil.
"Normally, from a fishery agency perspective, it would be a real concern to put rock barriers in some of these locations. But this isn't a normal water year," she said.
The dams would be made of 24-inch rocks at the entrance to three Delta channels, including False River near Oakley, just west of Franks Tract. The other two dams would be at Sutter and Steamboat sloughs on the Sacramento River near Courtland.
Rocks would be barged in and positioned by cranes. The state would remove the barriers in late November and put them back next year if the drought continues.
Holderman said the plan is to get the barriers in place as soon as May 1, which means working at a frenzied pace to get permits and notify property owners who could be affected. Among agencies that still must approve the plan are the State Water Resources Control Board, the U.S. Army Corps of Engineers and the National Marine Fisheries Service.
Contra Costa Water District is closely watching the project because of its potential to protect drinking water quality, said spokeswoman Jennifer Allen.
In the last two months, the district has pumped drinking water from Middle River because water from Rock Slough, near Knightsen, was getting too salty.
Salt in Rock Slough water now exceeds 180 parts per million chlorides -- 200 parts is considered the level when it can be tasted -- while Middle River water is about 100 ppm chlorides, the district said Wednesday.
"We're in an extraordinary time with the current drought, and not knowing what the summer is going to bring," said Allen. "We're looking at any option to protect our water quality as this drought continues."
Salinity at the giant state water pumps near Tracy is about 100 ppm chlorides -- well within a 250 ppm state standard. However, as the rainy season ends, water experts expect salt content to creep upward.
Some North Delta farmers say the barriers could make their irrigation water even saltier and harder to get by disrupting upstream flows that freshen up their Delta water.
"It worries me a lot," said J.B. Morais, owner of Delta Islands Organic Farm on Sutter Island. He recently invested in a new irrigation pump to tap his water rights in Steamboat Slough, and now isn't sure he'll be able to reach that water at all.
"My main concern is that people up here are going to be denied good water," he said.
Cate Kuhne, a Bradford Island property owner, says she worries about the dam limiting a key waterway for boaters, forcing them to detour toward narrower channels, jeopardizing island levees.
But, still, she says something must be done to address the water quality fallout from the drought.
"It's kind of a Catch-22. There are a lot of questions that haven't been addressed yet," she said.
State officials on Tuesday will be at a Bethel Island meeting to get a permit for the barriers from Reclamation District 799. The 10 a.m. meeting will be at the district office, 6325 Bethel Island Road, Bethel Island.
McClatchy News Service contributed to this story. Contact Denis Cuff at 925-943-8267. Contact Paul Burgarino at 925-779-7164.