California to dam Delta sloughs if drought persists
03/11/2014 8:53 PM
10/07/2014 9:16 PM
In yet another sign of the severe drought facing California, state water officials are planning to temporarily dam three channels in the Sacramento-San Joaquin Delta to control salinity intrusion from San Francisco Bay.
The California Department of Water Resources is working to place the barriers as soon as May 1, if the drought persists. The agency is scrambling to obtain the necessary permits and notify property owners who could be affected.
The temporary dams would consist of rock barriers piled across the entrance to three Delta channels: Sutter Slough and Steamboat Slough, branching off the Sacramento River near Courtland; and False River, branching off the San Joaquin River near Oakley.
In the case of the first two sloughs, DWR project manager Mark Holderman said the goal is to make the most of limited freshwater outflows that might be available in the main stem of the Sacramento River. The barriers would allow that fresh water to be held in the river, rather than branching into the side channels. This would concentrate its force and better hold back sediment that naturally would creep in from San Francisco Bay as river flows dwindle because of the drought.
The False River barrier is meant to keep salinity from seeping into the central Delta, where it could become trapped, potentially harming water quality for a prolonged period.
The urgency of the project is a reminder of how important Delta water supplies are to many facets of the California economy. The Delta is the natural collection point for about half of all the precipitation that falls on California. About 25 million people from Napa to San Diego depend to some degree on fresh water diverted from the Delta, along with about 3 million acres of farmland.
Holderman said one motivation for the project is to prepare for the possibility that the drought could continue into 2015. Controlling salinity levels in the Delta this summer, he said, would help ensure the estuary can be used to distribute limited freshwater supplies next year.
“It really creates all kinds of problems if we let the Delta get too salty,” Holderman said. “I would say it’s about a 95 percent chance we are going to put the barriers in. It’s just a matter of when.”
For water agencies that divert from the Delta, the project could be crucial to maintaining water quality this summer. This is particularly true for Contra Costa Water District, which serves about 500,000 people and draws almost all its water from the west Delta, where salinity is a perennial challenge.
“Without any additional rain or outflow coming from upstream storage, there could definitely be some impacts to water quality,” said CCWD spokeswoman Jennifer Allen.
But installing the barriers could pose threats to communities in the north Delta. A number of farmers on Sutter, Ryer and Grand islands divert water from Sutter and Steamboat sloughs for irrigation. The rock barriers could make their water saltier and more difficult to access by cutting off freshwater inflow from upstream.
“It worries me a lot,” said J.B. Morais, owner of Delta Islands Organic Farm on Sutter Island, which grows tomatoes and other crops for Sacramento’s Corti Bros. market and area restaurants. 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. It worries me they are going to design a system that cuts off a good portion of Delta irrigation to a large number of farmers.”
Gilbert Cosio, a civil engineer at MBK Engineers in Sacramento, represents a number of reclamation districts that manage levees and water supply on the islands adjacent to Sutter and Steamboat sloughs. He said water quality for any farmers drawing from the sloughs downstream of the proposed barriers could be “very, very bad,” severely reducing crop yields.
“The ones on the downstream side of the barriers are going to suffer, because that salt’s going to come in and just stack up,” Cosio said.
The last time the state deployed Delta barriers in a similar manner was during the 1976-1977 drought, one of the worst in California history. The barriers proposed this year, however, would be slightly different, Holderman said.
The barriers on Sutter and Steamboat sloughs each would have four sections of 4-foot diameter steel pipe, or culverts, installed with gates to allow a limited amount of Sacramento River water to pass through downstream, if necessary. “Through monitoring we’ll be doing, we’ll be able to open the culverts if we need to improve circulation downstream,” said Holderman.
In addition, on Steamboat Slough – a channel popular with summer boaters – the barrier would incorporate a boat launching facility operated by DWR. Vessels wishing to pass upstream or downstream would be put on a trailer, towed over the barrier and relaunched. But it could only handle boats smaller than 25 feet. Larger vessels, including houseboats and sailboats, would have to take a long detour via the Sacramento River.
Each barrier amounts to a small dam made of rocks 24 inches and smaller, spanning the width of each channel, Holderman said. The rocks would be brought in on barges and positioned by cranes. The goal is to remove the barriers by November, before the next rainy season.
Holderman estimates the project would cost between $25 million and $40 million, not including removal in the fall. He said DWR is still figuring out how to pay for it. “We’re moving very quickly, and it’s almost an impossible task,” he said.
Some Delta farmers, including Morais, suspect the intent of the barriers is to divert more fresh water to Southern California. The project would result in more fresh water passing through Georgiana Slough and the Delta Cross Channel Gates, where it then would be available for diversion by the state and federal water pumping systems in the south Delta near Tracy.
Holderman denied that is one of the goals, as did Terry Erlewine, executive director of the State Water Contractors. Both noted the water diversion pumps already have been restricted by state water quality officials to diverting Delta water at only 1,500 cubic feet per second, about 20 percent of full capacity, and only for urban purposes. Recent storms have permitted some exceptions, but that won’t continue without a major change in the weather.
“I’m expecting our water supply would be the same with or without these barriers in,” Erlewine said. “What we see these doing is, it lets you meet essentially the same water quality standards with a lesser amount of outflow.”
Among the agencies that still must approve the barriers are the State Water Resources Control Board, the U.S. Army Corps of Engineers and the National Marine Fisheries Service.
The latter agency is charged with protecting chinook salmon, which will be migrating downstream to the ocean in May. Those salmon are known to use Sutter and Steamboat sloughs; the barriers would block those paths, forcing the fish to remain in the mainstem of the Sacramento River.
Maria Rea, Sacramento-area supervisor at the fisheries service, said her agency has been advising DWR as it plans the barrier project.
“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,” said Rea.
Delta residents complain that DWR hasn’t provided enough information about the proposal to help them understand how they would be affected. Holderman said he expects to have more details to share by the end of this week.
“We don’t really know what is going on,” said Tim Neuharth, a longtime farmer on Sutter Island. He remembers the 1976-1977 drought, when a similar barrier that blocked off Steamboat Slough caused a lot of problems.
“We had about a 2-foot difference in water elevation vs. the upstream side of these dams, which caused a lot of havoc on our pumps,” he said. “They’d start sucking air, and then they’d cavitate, and then you’re done pumping. And they want to do this in July, which is the peak of our irrigation season.”
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