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BAY-DELTA FWO: 2014’s Gravel Replenishment Program in Nimbus Basin Continues Successful Run
California-Nevada Offices , September 10, 2014
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The 2014 gravel replenishment project below Nimbus Dam on the American River near Sacramento began August 4 and took about a month to complete.
The 2014 gravel replenishment project below Nimbus Dam on the American River near Sacramento began August 4 and took about a month to complete. - Photo Credit: USFWS
The project helps meet the requirements of the 1992 Central Valley Project Improvement Act, to restore and replenish spawning gravel and rearing habitat.
The project helps meet the requirements of the 1992 Central Valley Project Improvement Act, to restore and replenish spawning gravel and rearing habitat. - Photo Credit: USFWS
Biologist Julie Zimmerman of the USFWS Bay-Delta FWO is the project's co-lead.
Biologist Julie Zimmerman of the USFWS Bay-Delta FWO is the project's co-lead. - Photo Credit: USFWS

By Steve Martarano

Work began on the American River August 4 for its yearly project to restore quality spawning and rearing habitat for harmed species such as Chinook salmon and steelhead. The tremendously successful program, officially called the 2014 American River Salmonid Spawning and Rearing Habitat Restoration Project, wrapped up its seventh year, despite yearly roadblocks, such as the current drought.

Every year since 2008, U.S. Fish and Wildlife Service, Bureau of Reclamation (BOR) and its partners, designed and then implemented a gravel addition project in cooperation with other agencies’ involvement. Julie Zimmerman, a fish biologist with the Services’ Bay-Delta FWO, continues her role as a co-lead along with John Hannon of BOR. The other Bay-Delta FWO participant is Hydrologist Craig Anderson, who, along with Zimmerman, is on the American River Gravel Team.

Zimmerman said the yearly projects are needed because good quality spawning and rearing habitat for Chinook salmon and steelhead is limited on the Lower American River. She added that “gravel had been removed from the river during gold mining operations in the 1800s, so we're adding back a resource that was originally part of the American River.” Zimmerman added that a primary reason for the lack of habitat is the Central Valley Project (CVP) dams (Folsom and Nimbus) block gravel from upriver and don't allow it to move downstream to spawning locations.

Work that began Monday, August 4 between Nimbus Dam and Hazel Avenue finished in early September. The 2014 project continues the work of improving spawning and rearing habitat for steelhead trout and Chinook salmon in the lower American River. Much of the existing spawning habitat consists of large rocks and fine sediment that reduces the ability for the fish to construct redds (nests) and may reduce the number of eggs surviving and emerging as juvenile fish. A 350-yard-long side channel was excavated along the south side of the river in the Nimbus Basin using an excavator, and spawning gravel was added to the side channel and main river channel using front-end loaders and bulldozers.

The project helps meet the requirements of the 1992 Central Valley Project Improvement Act, to restore and replenish spawning gravel and rearing habitat. Tree planting at the site was expected to be done at a later date.

One way the drought has impacted the project this year has been the availability of dead trees, which are added to side channels to provide rearing habitat. In the past, project members had trouble finding trees to use. But this year, because of the drought, the parkway is losing up to two dying trees per week, so there’s been a consistent supply.

The trees provide organic matter that increases food supply, cover for juvenile fish to hide from predators, and hydraulic conditions (slow water next to faster moving water) that allow fish to conserve energy while feeding. All of these benefits contribute to growth and survival of juvenile salmon and steelhead.

The location of this year’s project, at the base of Nimbus dam, will help to provide the lowest available water temperatures for spawning salmon and juvenile steelhead during drought conditions. During the summer and early fall, the lowest water temperatures in the lower American River are found at the base of Nimbus Dam and water gradually warms as it travels down river. During drought conditions, low storage in Folsom Lake limits the availability of cold water to release for the benefit of salmon and steelhead. Creating spawning and rearing habitat in areas of the coolest available water helps to mitigate for some of the effects of the drought.

With eight projects now complete, are the projects working? “They definitely are,” Zimmerman said. “We do a lot of monitoring every year, which includes taking several aerial photos, and we can see that the sites are being used very heavily. Our monitoring also shows we’re creating plenty of rearing habitat.”

The American River gravel program team includes personnel from several state and federal agencies. The team provides input on most aspects of each year's project, including selecting project sites, project designs, monitoring, and adaptive management plans. They provide input to the team leaders, who make the decisions on what is implemented and funded (through the CVPIA).

Steve Martarano is the public affairs specialist at the Bay-Delta Fish and Wildlife Office in Sacramento, California.

 


Contact Info: Steve Martarano, 916-930-5643, steve_martarano@fws.gov
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