Major reservoirs in the Mother Lode are releasing water at a rate roughly 10 times greater than the 15-year median for this time of year as dam operators make room for runoff from a snowpack that’s well above average.
Goodwin Dam downstream of Tulloch and New Melones reservoirs on the Stanislaus River were releasing about 4,500 cubic feet, or 33,000 gallons, per second on Thursday. The 15-year median for this time of year is about 451 cubic feet per second, according to data from the U.S. Bureau of Reclamation.
The bureau operates the dam that holds back water in New Melones Reservoir and started ramping up releases in late February, according to Todd Plain, spokesman for the bureau’s Mid-Pacific Region.
Plain said the releases are expected to continue at roughly the same rate of 4,500 cubic-feet per second for the next several weeks in anticipation of heavy inflows from a snowpack that is about 165 percent of the historical average for this time of year and far greater than last year.
“That’s why we’re not cutting releases yet,” he said. “We’ve had some pretty significant storms right above the reservoir and tracking another one about a week away.”
The inflow into the reservoir overnight Wednesday into Thursday was about 7,000 cubic-feet per second, according to Plain.
New Melones Reservoir was holding just over 2 million acre-feet of water as of Thursday, about 84 percent of the maximum capacity of 2.4 million acre-feet and about 134 percent of the average for this time of year.
Water released from New Melones Dam flows into Tulloch Reservoir, which held just over 56,000 acre-feet on Wednesday, or about 84 percent of the maximum capacity of 67,000 acre-feet and 97 percent of the historical average for the date.
Tulloch is operated by the Tri-Dam Project, a partnership between the Oakdale and South San Joaquin irrigation districts, which also operates Beardsley and Donnells reservoirs upstream of New Melones.
It’s all part of a complicated balancing act for dam operators in the Stanislaus River watershed to maximize water storage while protecting people, property and the environment downstream of the reservoirs.
Construction of New Melones Dam was authorized by Congress in 1944 to prevent flooding of 35,000 acres of agricultural land and communities in the valley, which Plain said has only become more complex since that time as the downstream population has grown.
Plain said the dam wasn’t constructed to be overtopped. Allowing the reservoir to get too full could present “unreasonable risk to the public, property and environment.”
“We’re constantly monitoring current conditions, which includes precipitation, forecast, and snowmelt,” he said. “There’s also side flows that come into Tulloch that you have to consider… We don’t want to indundate Tulloch with our water from New Melones when they also have side flows coming in from other tributaries.”
In addition to flood control, New Melones is part of the Central Valley Project that was devised in 1933 to provide water from the northern half of the state — where about two-thirds of the state’s water originates for irrigation and municipal water in the Central Valley — where two-thirds of the state’s agricultural land is concentrated.
Susan Larson, spokeswoman for the Tri-Dam Project, said they follow schedules for water releases that are enforced by the bureau.
“It’s a coordinated effort, but I think we do a great job protecting the public from downstream flooding by being so coordinated with the feds, PG&E, and all of us on the river system.”
Larson said the higher than average flows means that people should exercise caution around rivers and streams in the Mother Lode now and into the summer months.
A five-year-old girl recently died after falling into the Stanislaus River near Knights Ferry on March 17. Tri-Dam and Bureau officials said they worked together to reduce the flows for several days to aid in the search for her.
Contact Alex MacLean at firstname.lastname@example.org or (209) 588-4530.