How Collaborative Efforts are Reviving a Vital Ecosystem in the San-Joaquin Delta

In the last five years, the Department of Water Resources (DWR) and its partners have restored thousands of acres of tidal wetlands and floodplains along the Sacramento River and in the Delta, where the Sacramento and San Joaquin rivers tangle on their way to San Francisco Bay. These newly-restored habitats already pay dividends for threatened and endangered fish species. Recent studies show native fish species using these restored habitats – in some cases, within months of project completion. The newly-created habitats provide additional spawning areas for native fish and good feeding and resting spots for salmon migrating to the ocean.

Using new advances in science and monitoring, DWR designed restored habitats using a “corridor concept.” The work aims to give Delta smelt, longfin smelt, and Chinook salmon what they need along their direct migratory routes, helping to keep the fish away from the main pumping plant of the State Water Project, operated by DWR along a south Delta channel near Tracy. When monitoring shows endangered or threatened fish species near the pumps, DWR modifies its operations. Recent improvements in fish populations reflect the combined effects of habitat restoration, operational measures, and hatchery and harvest practices, underscoring the need for continued collaboration across government agencies.

Before people built levees and channels to drain the land, the Delta featured a vast, rich mosaic of tidal and freshwater marsh and upland habitat. Each of DWR’s habitat restoration projects returns a bit of this highly transformed land to better conditions for fish and wildlife. Since 2020, DWR and its partners have completed 16 separate projects enhancing and protecting approximately 7,000 acres within the Delta region – about 11 square miles. Another six habitat restoration projects are under construction or in the planning stage. DWR last month celebrated completion of a significant state and federal project to modify the Fremont Weir so that fish and water can move more easily from the Sacramento River onto thousands of adjacent acres of floodplain habitat and back into the river. Seasonal inundation of floodplains like this creates ideal conditions for growth of the microscopic plants and animals that nourish fish. DWR opened the gates on the newly revamped Fremont Weir for the first time this month.

All this “green” infrastructure allows for mutual protection of species and water supply for 27 million Californians.