Temperature plan could cut yield from Shasta Lake
By Christine Souza
Even as storage in Shasta Lake has risen to more than 135 percent of average, a fishery agency's recommendation could require more water to be held behind the dam through the spring and summer—effectively reducing the amount available for downstream human and environmental uses.
A draft proposal by the National Marine Fisheries Service recommends changing temperature-management guidelines for the reservoir, requiring the U.S. Bureau of Reclamation to keep more water in it to ensure sufficient cold water for federally protected winter-run chinook salmon. The suggested change, part of a larger effort by fisheries agencies to benefit the salmon, is expected to impact those who depend on water from Shasta Lake—including the federal Central Valley Project.
Ara Azhderian, water policy administrator for the San Luis & Delta-Mendota Water Authority, said if more water is retained in reserve for temperature control, the result would be "less water to irrigators, less to wildlife refuges, less to cities, less for other species, less for delta outflow—so less all around."
Faced with high winter-run salmon mortality rates, especially during dry years, NMFS wants the Bureau of Reclamation, which operates Shasta, to use stored water to reduce Sacramento River water temperatures from mid-May through October to protect spawning fish. As part of the draft proposal, the bureau would study a new temperature regime for the remainder of the year. The process is expected to result in development of a final proposal and would likely inform the next biological opinion for the winter-run chinook.
Louis Moore of the Bureau of Reclamation Mid-Pacific Region said it is early enough in the process that fisheries agencies are still trying to figure out how to move forward.
"It's an ongoing discussion and will continue until folks come up with what's the best practice," Moore said. "(Temperature management guidelines for Shasta) are being updated to look at all of the new considerations and new data requirements. This is an important step as they continue to do this review and come up with the best approach."
California Farm Bureau Federation environmental policy analyst Justin Fredrickson said ultra-conservative temperature control operations in 2016 kept the river cold, but so much water was held back through the summer that the end of the irrigation season saw 225,000 acre-feet of water stranded in Lake Shasta—enough to irrigate nearly 100,000 acres of land in the western San Joaquin Valley. He said that water was subsequently lost to flood control operations, while providing no additional benefit to the salmon.
CVP agricultural contractors south of the Sacramento-San Joaquin Delta received just a 5 percent water allocation last year, and almost had even that water cut off last summer. That followed a complete shutoff of CVP water the previous two years.
Azhderian said the regulatory activity on water temperature stems from the 2014-15 water year, when winter-run salmon experienced an especially high mortality rate—97 percent—reportedly due to warm Sacramento River temperatures. Results improved last year, when the winter run experienced only a 3 percent mortality rate, attributed to improved water conditions.
Because salmon and their eggs are sensitive to water temperatures and are damaged or destroyed when temperatures rise above 56 degrees, NMFS, also known as NOAA Fisheries, has issued the draft recommendation on river water temperature.
"You have two drivers behind this proposed change," Azhderian said. "One is the perspective that Reclamation had missed temperature targets in the past, and there's the drought—the estimated low egg survival that occurred in 2014 and 2015. As a species that has lost two of the three years' breeding stocks, the rationale by NMFS is we must do really aggressive things to save the species from going extinct."
Acknowledging the winter run to be "in bad shape," he said water agencies are nonetheless frustrated by a "more-of-the-same strategy" focused solely on water temperature.
"The temperature can be perfect, but if the spawning bed is choked with algae and weeds, then fish aren't going to spawn in it. Our interest is to really round out what it is we begin to look at, so that we can ultimately begin solving this problem," Azhderian said.
Glenn-Colusa Irrigation District general manager Thaddeus Bettner said the NMFS proposal would have domino effects throughout the water system.
"For us who divert water from the Sacramento River, this puts our diversions at risk. For folks south of the delta, that puts exports at risk. For the diverters and users on the American River who rely on Folsom Reservoir, that results in Folsom Reservoir being drawn down as well as Oroville. Because the systems are so integrally operated and connected, changing that one operation at Shasta just reverberates through the system and potentially causes negative effects," Bettner said.
Shasta Lake has a storage capacity of 4.5 million acre-feet, he said, with flood stage considered to be 3.2 million acre-feet. But Bettner said the NMFS plan would shrink the reservoir's effective capacity to a couple of hundred thousand acre-feet.
"It is built to be more flexible and when you take the flexibility out of it, beneficiaries are going to suffer," he said.
Fredrickson said water users remain concerned about the fish, but said actions must be "reasonable and supported by science" to ensure the best outcome.
"In the drier years especially, our statewide water supplies are limited and we simply cannot operate our key reservoir in the state to serve just one purpose," he said.
Azhderian said the 2016 water restrictions in the name of river temperature caused "all sorts of socioeconomic disruption" that continues to be felt in areas where water supplies were restricted.
"We know (the proposal) would create impacts, because we saw the impacts that last year's operations created and we would assume that they would be similar," he said. "But simultaneously, we want to invest our energy in: What else can we be studying? How can we dedicate our experts and resources in helping develop a sustainable solution?"
(Christine Souza is an assistant editor of Ag Alert. She may be contacted at firstname.lastname@example.org.)
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