Storm flows lead to challenges for water system
December 30, 2014
After enduring three of the driest years in state history, nothing could be more heartening to farmers and ranchers than the steady march of Pacific storms that reached California this month. But good news is tempered by the knowledge that a few strong downpours don’t translate into full reservoirs and abundant supplies — and the storms revived concern about how state and federal water systems manage storm flows in a drought year.
The state’s reservoirs stand at about 57 percent of average, slightly below this time a year ago and well below full capacity.
“We’ve had years past where rain and snow didn’t continue into the New Year,” said State Climatologist Mike Anderson, pointing to the moisture cutoff last January that assured shortages for farmers who rely on surface water deliveries from the state and federal water projects.
“So far this year, precipitation levels depend on where you are—north of a Bay Area-Tahoe line, precipitation is above average, but in the south, levels are actually below average,” Anderson said. “In addition, there’s also below-average snowpack across the entire Sierra Nevada.”
He said most of the storms so far this water year, which began Oct. 1, have been warm, meaning snow accumulations aren’t building the way water managers hope. Sierra snowpack currently is about 50 percent of average, he said.
While December storms dropped significant precipitation, the California Farm Water Coalition noted last week that many of the state’s agricultural customers in the federal Central Valley Project worry that this year’s zero deliveries of surface water will be repeated in 2015.
“In the last few weeks, hundreds of thousands of acre-feet of water were in the system at the same time delta pumps were almost completely shut down,” coalition Executive Director Mike Wade said.
As these storms have come in, Wade said the water storage situation is similar to what was seen a year ago—except the state’s reservoirs are now lower.
“It’s very frustrating to watch water flowing through the system without being captured,” he said. “We have constraints in the delta that hold down the amount of water we catch to the bare minimum because of protections for delta smelt.”
During the height of the stormwater pulse moving through the Sacramento-San Joaquin Delta last week, he said, less than 10 percent of the surge was captured for storage and use next summer.
The state Department of Water Resources and U.S. Bureau of Reclamation, in conjunction with the U.S. Fish and Wildlife Service, said last week they are experimenting with pumping reductions to prevent a “turbidity bridge” from occurring in the central and south delta. Delta smelt are attracted to turbid, or cloudy, water because it makes the tiny organisms it feeds on more visible and provides shelter from potential predators, such as non-native bass.
DWR described the strategy this way: “Forgoing the capture of tens of thousands of acre-feet of water may allow water project operators to avoid the loss of hundreds of thousands of acre-feet of water supply later in the winter.”
A spokeswoman for the Bureau of Reclamation, Erin Curtis, said the storms present challenges in operating the system “to balance the critical need to quickly increase water supplies south of the delta while being cautious to not trigger environmental restrictions that could constrain delta operations and ultimately reduce the overall supplies.”
Representatives of agricultural water users said they’ll be closely watching the results of the operational change.
“It will be interesting to see if this is a worthwhile new operating principle at the beginning of each season,” said Chris Scheuring, an environmental attorney for the California Farm Bureau Federation. “The downside is that it might turn out to be a waste of water.”
“Clearly there is risk associated with a decision like this,” Wade said. “We hope the risk pays off.”
Fresno County farmer Dan Errotabere said due to the “turbidity bridge” theory and the lack of water transfer from the delta into storage, there’s serious concern about water supply management on the part of San Joaquin Valley farmers who rely on the state and federal projects for water deliveries during the growing season.
“Managing water during a drought is critical,” Errotabere said, noting that he fallowed 1,200 acres this year. “We’re losing opportunities now and, if the available supplies aren’t managed to capture available water to the fullest extent, we may not see a water allocation for the next crop year.”
He said he’s grateful for recent rainfall that helped reduce the need for irrigation of his winter garlic and wheat crops. The rain also helps leach salt, which has built up in the soil due to the region’s widespread use of drip irrigation and saltier groundwater.
“We’ve got to get off the groundwater because of its lower quality,” said Errotabere, who is vice chairman of the CFBF Water Advisory Committee, “and we need legislation to make sure good-quality irrigation water is put into storage. The rainy days are slipping away and we may find there’s no more available water to capture.”
Vince Dykzeul, a diversified grower from Modesto, urged creation of new water storage to help water managers respond to the ebb and flow of storms.
“If it’s true the climate is changing,” Dykzeul said, “if we’re going to have larger storms and longer droughts, then we need more water in storage to respond to these changing conditions. Water storage increases system flexibility and, if done right, everybody wins from having more water available.”
He noted that his farming operation is particularly vulnerable to flooding.
“Without adequate infrastructure to control storm waters, that’s when we have trouble,” Dykzeul said. “Nobody wants to talk about managing flood while managing through a drought, but I know the benefit of keeping both sides of the coin in mind.”
Federal weather forecasters said last week they expect continued average to above-average rainfall across California during the next three months, predicting an easing—but not an end—to the severe drought of the past several years. There’s also a 65 percent chance of weak El Niño conditions developing in the Pacific Ocean, which could influence winter precipitation, although experts say “anomalies” in climate patterns create forecast uncertainties.
“It’s not likely the drought will be broken this year,” said Steve Baxter, a National Oceanic and Atmospheric Administration forecaster. “But it’s likely (California drought) conditions will improve.”