LA GRANGE — Construction of the Tuolumne River Mainstem Channel Restoration project, which aims to provide healthy habitat in which fish can thrive, was completed this week by partners Turlock Irrigation District, Modesto Irrigation District and the San Francisco Public Utilities Commission.
The three utilities provided more than 7.5 acres of mainstem restoration, more than 2.5 acres of floodplain habitat, and more than 50,000 cubic yards of spawning gravel, which is expected to result in a five-fold increase of trout and salmon habitat about 1.5 miles upstream of Old La Grange Bridge.
“We remain committed to be good stewards of the Tuolumne and implement solutions to provide a healthy river habitat,” said TID General Manager Brad Koehn. “There is new spawning and in-channel habitat, and we’re encouraged as we’re already seeing fish spawning in the new gravel.”
Spawning habitats were created by cleaning, washing and returning gravel to the lower Tuolumne — in the form of riffles and gravel bars where the fish thrive — that originally was removed from the river during California’s Gold Rush of the mid to late 19th century. In addition to the creation of a spawning habitat, large wood features and boulder clusters were added to increase in-channel habitat diversity.
Peter Drekmeier, the policy director for Tuolumne River Trust, praised the utilities for the habitat restoration component, but reminded that floodplain restoration is an equally important part of the puzzle.
“My main concern is that we’re just focusing on spawning and gravel augmentation, which will likely result in more baby fish,” said Drekmeier, who pointed out that TRT recently completed a restoration project downstream of the Old La Grange Bridge. “But if those baby fish don’t have a safe place to rear, like floodplains, then they’re stuck in the main channel and become bass food. The bass population then grows, and the problem gets worse.
“This is a good start, but it’s just one piece of the puzzle. And without the other piece, it won’t work.”
The Bay-Delta Water Quality Control Plan calls for 40 percent unimpaired flow on the Tuolumne between February and June, with those being critical months for rearing and subsequent out-migration of juvenile fish.
According to Drekmeier, if established biological goals are met, that threshold could be reduced to 30 percent unimpaired flow — meaning utilities would have to release less water. If the goals are not met, the threshold could rise to 50 percent.
“That’s a strong incentive for water agencies to implement non-flow measures that will help meet the biological goals and reduce the amount of water required to be left in the river,” said Drekmeier.
Project design and implementation was led by Applied River Sciences in collaboration with and the U.S. Fish and Wildlife Service, California Department of Fish and Wildlife and the Tuolumne Band of Me-Wuk and Northern Valley Yokuts tribes.
“There is tremendous power in partnerships,” said Dennis Herrera, General Manager of the SFPUC. “Together, we’re doing the work to protect and restore native fish populations on the Tuolumne River.
“The Old La Grange Bridge Habitat Restoration Project is also a preview of the future. This project is an example of many projects to come as part of our longer-term commitment to significantly invest in restoring habitat on the Tuolumne as part of the Healthy Rivers and Landscapes Program.”
The project began in June and was completed four months later in mid-October. The total cost of the project was estimated at $7.8 million, including funding from a grant from the CDFW, coupled with MID, TID and the SFPUC’s self-funded commitment of $2.3 million, and was completed under budget, according to TID.
“After years of studying the river, we are thrilled to apply what we’ve learned and execute solutions with real-life benefits,” said MID General Manager Jimi Netniss. “This is one of many projects to come that solidifies our commitment to creating a vibrant environment for Tuolumne River fish.”
TID, MID, and the SFPUC made a commitment of $80 million to design and implement a habitat restoration program along the lower Tuolumne River as part of the Healthy Rivers and Landscapes Program. By 2030, and with the help of renowned experts River Partners and Applied River Sciences, the utilities hope to develop 77 acres of suitable salmon rearing and floodplain habitat and add approximately 100,000 tons of gravel in specific reaches of the river for optimal spawning and rearing.
