Restoration of Dutch Slough

In the city of Oakley, Dutch Slough has one foot on the reed-covered banks of the Delta in northeastern Contra Costa County and the other toe-to-toe with a housing development. Great blue herons, egrets, and blackbirds frequent this 1,166-acre freshwater tidal marsh and upland site, once slated for 6,000 houses. The slough is now the focus of a collaborative effort between the state Department of Water Resources, CALFED ’s Bay-Delta Program, the state Coastal Conservancy, the nonprofit Natural Heritage Institute, and the city of Oakley. A model restoration project, Dutch Slough is the only site in the central or western Delta with the necessary elevation for large-scale tidal restoration. Conceptual plans and feasibility studies are slated for completion in February, and project leaders are seeking funds for the restoration work.

The Delta needs some good news. Recently the Bay Institute, a nonprofit, science-based advocacy organization based in Novato, gave the northern Bay near the Delta failing grades, stating that “populations of native fish and other aquatic organisms, from the bottom to the top of the food web, have crashed.”

The recent decline of Delta smelt, a small fish listed as threatened under the Endangered Species Act, is of great concern, says Bruce Herbold, a U.S. Environmental Protection Agency biologist involved in the Dutch Slough work. Herbold says the smelt are a good indicator of the Delta’s broader problems, and whatever is killing the smelt may affect other species as well.

“There are very few smelt out there,” he continues. “In 2004 smelt reached their lowest numbers on record and they were a tenth of that in 2005. If that’s not a prelude to extinction, it’s hard to say what is. We’re not sure what to do to address their decline. The main thing we’ve done so far is change water project exports so they’re taking less water in the spring when smelt are spawning. Since the smelt continue to decline, it isn’t enough.”

In October, the state Resources Agency announced a “Delta Smelt Action Plan,” developed with the state Departments of Fish and Game and Water Resources. The 14-point plan will examine probable causes of the decline, such as agricultural and urban pollution, invasive species, and water exports. It will also evaluate possible responses, such as restoration projects and changes in the management of water deliveries and power plant intake. Download the full plan as a 1.3 MB PDF.