Work is under way on a mile-long stretch of Dry Creek to create habitat for coho salmon and steelhead, both native fish that need pockets of slow-moving water to survive.
"We are adding a lot of large wood and rock to provide cover and refuge from the flow in the summertime and the wintertime for these endangered and threatened fish," said Dave Manning, a Sonoma County Water Agency principal environmental specialist.
"Water quality and water temperatures are excellent, but in many places the water flows more swiftly than what the fish would prefer for rearing," Manning said.
Coho salmon were on the verge of extinction just a few years ago but are now being found in encouraging numbers.
Coho are on the endangered list, while steelhead and chinook salmon are on the threatened list.
"We have caught more out-migrating coho juvenile fish than in previous years, and we have found juvenile fish rearing in Dry Creek this summer," Manning said. "We still find relatively small numbers, certainly many, many times fewer than the number of steelhead or chinook; we find handfuls of coho and many thousands of steelhead and Chinook salmon."
The water agency was ordered four years ago by the National Marine Fisheries Service to improve conditions in the Russian River, Dry Creek and tributaries.
The work, estimated to cost $150 million over 15 years, includes in-stream work in Dry Creek to improve habitat, a reduction of the summer flows in the Russian River and the creation of a fresh-water lagoon at the mouth of the Russian River at Jenner.
The habitat in Dry Creek and its tributaries has gotten a lot of attention the past few years.
The U.S. Army Corps of Engineers next week will also be working to restore a stretch of Dry Creek within the Lake Sonoma park boundary.
The Sotoyome Conservation District is finishing restoration work on 3,000 feet of Salt Creek, which will prevent sediment from entering that tributary in the Dry Creek system.
Dry Creek is important as the outlet for Lake Sonoma, which provides the bulk of the water for 600,000 Sonoma County Water Agency customers in Sonoma and parts of Marin County.
Manning said that with the in-stream work, the water agency hopes to be able to provide habitat for coho and steelhead without having to reduce the flow of Dry Creek or, as a last resort, build an additional pipeline to Lake Sonoma that could cost $141 million.
Coho and steelhead thrive in cold, slow-moving water where they can spend one to two years before migrating to the ocean.
The Dry Creek work is costing $6 million for the mile stretch, with work on another five miles expected to cost another $30 million to $42 million.
The cost of the Dry Creek work is being paid for by Sonoma County taxpayers as part of an assessment on the maintenance of Warm Springs Dam and by the Army Corps of Engineers.
Dry Creek today is much different from when it was natural. It now runs year-round because of releases from the dam. It is also in a channel between vineyards, rather than meandering through and flooding Dry Creek Valley each winter.
The intention is not to restore Dry Creek, but to create the habitat necessary to maintain the fishery for coho and steelhead.