Reclamation funding spurs work on broad tidal habitat restoration project
Prospect Island, right is bordered by Miner Slough
WALNUT GROVE, Calif. - Standing on the levee road, surrounded by trees and an inert slough, it’s hard to get a read on distance or orientation. But that’s the Delta – a mosaic of water, land and sky that harkens to an undiscovered part of California that defies time or categorization.
The Delta is critical to Reclamation’s Central Valley Project and the Department of Water Resources’ State Water Project operations – the hub where water flows in California. Improving the health of the ecosystem is equally important, an aim that pushes the construction and completion of ambitious and comprehensive restoration projects.
One of those undertakings, the Prospect Island Tidal Habitat Restoration Project, is being recognized this week by state and federal officials. Once part of the Delta’s patchwork of farmland, Prospect Island awaits a transformation that promises to return it to the tidal-driven wetland it was before levees blocked the connectivity. DWR is leading the $69.4 million project, with funding coming from Reclamation to support the Healthy Rivers and Landscapes Program.
Situated east of the southern end of the Yolo Bypass floodplain, Prospect Island is separated from that connection by the Sacramento River Deep Water Ship Channel. Restoring it emerged as viable tactic as fisheries biologists examined the means to improve habitat for native fishes struggling amidst the many stressors that inhibit their productivity.
The land is a remnant of the Delta’s agricultural legacy, so much so that its former contours can still be recognized. Its soils once hosted bountiful crops, the result of a landscape restructuring that fostered a thriving farm economy at the cost of about 250,000 acres of prime tidal wetland habitat Delta-wide, a loss that contributed to the sharp decline of native fish and wildlife.
The 1,600-acre Prospect Island is separated into two parcels – 1,300 acres on the north and 300 to the south. It’s thick and densely vegetated forest, with chalky, sandy soil.
“It is really just a giant bathtub,” said Dan Riordan, chief of the California Department of Water Resources’ tidal habitat restoration section.
Brian Mahardja, biologist with Reclamation’s Bay-Delta Office, said isolating land from water adversely affected the ecosystem.
“The native species of the Delta evolved with the presence of tidal wetlands as opposed to dredged and leveed open water channels,” he said. “Although the loss of tidal wetland is just one of the many issues that native species of the Delta are facing today, it’s likely to be an important one.”
Tidal habitat restoration is a staple of the many projects underway or completed in the Delta. The work is comprehensive and detail-laden, as crews work within narrow confines to reintroduce flows while staying mindful of flood control and other necessities. In the case of Prospect Island, it means breaching levees at key locations to usher the daily tidal cycle.
Returning Prospect Island to a version of its previous existence is a significant undertaking. It’s not a venture begun hastily or without vision, but environmental planners are eager to see the benefits: a supercharged food web, a haven to salmon and Delta smelt, improved water quality, recreational opportunities and the positive effect of carbon sequestration in tidal marshes.
Tidal habitat restoration returns ecosystem functions and absorbs floodwaters to buffer against sea level rise, support wildlife and improve water quality by filtering pollutants.
Prospect Island is a multi-purpose project that “checks off a lot of the boxes for our overall goals for the Delta,” said Reclamation’s Mahardja.
“It is meant to benefit listed species such as Delta smelt and Chinook salmon … but will likely also benefit other less-studied native fishes,” he said. “Tidal restoration may help buffer the system from the establishment of new invasive species and improve the local water quality.”
He noted, however, that the positive impact from restoration projects such as Prospect Island “will likely take years to be evident and may not necessarily be observable at the population level-scale.”
