Fish might get help past dams along Tuolumne River

Salmon leap over rocks and other small obstacles as they swim up the Tuolumne River to spawn every fall.

But they cannot surmount the 110-foot-tall dam that created La Grange Reservoir, much less the 585-foot dam just upstream at Don Pedro Reservoir.

A meeting this week explored how the fish could get to the upper river through structures that the Modesto and Turlock irrigation districts might have to build. They could cost as much as $110 million, based on a recent review of such projects around the West, but the districts might have no choice. Fish passage is a possible condition of new federal licenses for generating hydropower on the Tuolumne.

“There is a lot at stake,” said John Devine, a licensing consultant for the districts. “These are often costly and complicated structures.”

The meeting, held at MID’s headquarters, dealt with the study underway on the fish passage issue. It will look at various options – ladders, pipes, canals, trucking and others – for getting fish around the two reservoirs. Experts will try to determine how many salmon, as well as steelhead trout, used the upper river before the dams were built.

The districts have been working since 2011 on a renewal of the license that led to the 1971 completion of Don Pedro, their main source of water and hydropower. They completed La Grange in 1893, long before licenses were required. The Federal Energy Regulatory Commission ruled in 2012 that a license was needed, including exhaustive study of fish and other concerns.

La Grange covers about a mile of former river, while Don Pedro stretches across 23 miles when at capacity. About 2 miles of still-flowing river lie between the two reservoirs.

The two-year study will look at possible designs for fish passage, as well as costs. The review of other projects found one as low as $10 million.

Experts also are looking at conditions on the river above Don Pedro, including tree cover, spawning gravel and other features friendly to fish.

The flows here are not natural: They rise and fall each day with releases from the Hetch Hetchy Water and Power System, which supplies much of the San Francisco Bay Area. And climate change – a general warming of the planet – could mean that future conditions will not match those of the pre-dam days.

“Whether it might have been historical habitat, it has changed tremendously over the years,” said Devine, an engineer with HDR Inc., a global firm.

The districts already are dealing with state and federal efforts to increase lower-river flows to benefit salmon and steelhead, which would reduce water for farms and cities. Both types of fish spend part of their lives in Sierra Nevada streams, part in the Pacific Ocean.

The meeting included people from the district staffs, as well as consultants, fishery agency people, environmentalists and business interests. Tom Orvis, governmental affairs director at the Stanislaus County Farm Bureau, noted that few in the room were water or power customers of MID or TID.

“They’re the ones who are eventually going to be paying for it,” he said.

Patrick Koepele, executive director of the Tuolumne River Trust, said by email after the meeting that he hoped all parties could work together.

“Salmon and steelhead have lost at least 60 miles or 85 percent of historic spawning habitat, all of it the best habitat, due to man-made obstructions, so in our opinion, providing more spawning habitat will be a key to recovering these species,” he said.

This story was originally published May 21, 2015 at 5:53 PM with the headline "Fish might get help past dams along Tuolumne River."