Discussion returns on moving salmon above Don Pedro Reservoir

An intriguing and expensive idea – moving salmon to the Tuolumne River stretch just above Don Pedro Reservoir – will return for discussion Thursday.

The Modesto and Turlock irrigation districts will hold their fifth public workshop on the proposed fish passage, which could be a condition of a federal hydropower license.

The system would use motorized ladders, trucks, canals or some other means of getting salmon around Don Pedro, which covers about 30 river miles when full. Speakers at past workshops have said it could cost hundreds of millions of dollars, depending on the technology and scope.

Proponents say the system could greatly increase spawning habitat for salmon, which return to their native rivers after a few years in the Pacific Ocean. The Tuolumne segment at issue stretches more than 25 miles from the upper extent of Don Pedro to San Francisco’s diversion point near Yosemite National Park.

Critics say the districts’ water and power customers would bear the cost of the fish passage, which might end up aiding a small number of salmon.

The project would be a condition of a power license for La Grange Reservoir, a small impoundment 2 miles downstream of Don Pedro. The larger reservoir is undergoing a separate licensing process.

The Federal Energy Regulatory Commission is overseeing two years of study on the fish passage, ending in 2017. Experts are looking at the possible designs, cost and benefits – and whether salmon actually swam the upper river before La Grange was completed in 1893. They also are assessing whether the passage would benefit steelhead trout, another oceangoing fish.

Thursday’s agenda includes studies on river flows, spawning gravel, other creatures in the water and socioeconomic issues raised by the proposal.

This story was originally published May 17, 2016 at 1:15 PM with the headline "Discussion returns on moving salmon above Don Pedro Reservoir."