Federal agency reaffirms support for how MID, TID want to operate Don Pedro Reservoir
The owners of Don Pedro Reservoir have reached a key milestone in determining how much of its water goes to human uses and how much to Tuolumne River fish.
The staff of the Federal Energy Regulatory Commission stated its support once again for the fishery releases proposed by the Modesto and Turlock irrigation districts.
The action reaffirmed FERC findings in February 2019 that dismissed pleas from environmental and sport-fishing groups for much higher flows.
MID and TID say their plan will still boost water levels in the 52 miles of river downstream from La Grange, but not to a degree that harms their customers. They say more could be achieved for fish with nonflow measures such as restoring spawning gravel and floodplains.
The latest FERC staff action still leaves the districts at least a year from approval of a new license by the appointed commission, TID leaders said last week. But they are confident it will go through.
“This is an exciting time for the Tuolumne River,” TID board member Michael Frantz said after an update Tuesday on the process.
The term of the new license has not been decided, but it will be between 40 and 50 years, said John Devine, a consultant to the districts. It would replace the 1966 license that led to the completion of Don Pedro in 1970.
The latest FERC action was the release of a final environmental impact statement on the new license. The draft EIS, issued early last year for public comment, also agreed with the districts’ flow plan.
The final EIS still needs review by federal fishery agencies and the State Water Resources Control Board. The state board had voted in December 2018 for much higher releases. Gov. Gavin Newsom, who took office the next month, directed the board to seek a compromise with the districts. That process is still under way.
Water, power for farms, cities
Don Pedro is California’s sixth-largest reservoir at 2.03 million acre-feet, and the largest under local rather than state or federal ownership.
The districts supply about 208,000 acres of farmland in Stanislaus and Merced counties, a foundation of a vast food-processing sector.
MID treats some of the water for domestic use in Modesto and a few nearby locales, reducing their reliance on wells. TID will do the same for Turlock and Ceres via a treatment plant set for completion in 2023.
Don Pedro also generates hydropower for the districts’ electricity customers. It is cheaper than other sources but makes up far less of the supply than decades ago.
The hydropower part means that Don Pedro needs a license from FERC, including conditions on releases to the lower river. The renewal process launched in 2011 with a 2018 deadline, which was extended.
Enhancing fish habitat
Highlights of the districts’ plan for the Tuolumne:
- The fishery releases would not reduce water deliveries to farms and cities in years defined as wet, above normal, below normal or dry. In the worst kind of year, critically dry, 88 percent of demand could be met, down from 92 percent under the current rules.
- The increased flows would be most pronounced in the 26 river miles between La Grange and the Geer Road bridge. From there, some of the water would go to the treatment plant for Turlock and Ceres. It will have its biggest demand in summer and early fall.
- The remaining 26 miles past Geer would get a smaller increase during this time of year. This stretch of the Tuolumne winds past Ceres and Modesto before joining the San Joaquin River.
- Minimum flows would rise from October to December to help Chinook salmon returning to spawn after a few years in the Pacific Ocean.
- The boost would continue as new fish hatch and develop over winter and spring before heading out to sea. The volume would be far less than what the state board first proposed – 30 to 50 percent of the natural runoff from February to June.
The districts proposed $138 million worth of improvements to the river that they say would mesh with their increased flows. This includes building up gravel beds where salmon lay their eggs, which have been damaged by mining and other activities. The restored floodplain would be inundated at times to provide food and shelter for juvenile fish.
The plan included a few things that FERC rejected, including a salmon hatchery and efforts to reduce predation by striped bass and other non-natives.
Environmental perspective
The Tuolumne River Trust has been among the environmental groups seeking much higher flows. A representative could not be reached for comment on the latest FERC action.
The trust and its allies have argued that only about 20 percent of the Tuolumne remains in the channel after the diversions to local users and the Bay Area. It can be more like 10 percent in dry years, advocates say.
They say more water down the river would provide the cool conditions that salmon need, while also benefiting trout and other creatures. They also urge further water conservation.
“Higher flows and a strong local economy can be successful together,” the trust said in an online post last year. “Through better management of snowmelt, water-efficient irrigation practices and better crop selection, farmers can grow more food with less water.”
The trust cited a project involving Stanislaus River water used by the South San Joaquin Irrigation District. It replaced some of its open canals with a pressurized system that cut demand by 30 percent while increasing crop yields by the same percentage.
