Saving fish in the short- and long-term on the Naches River

Aerial view Naches tributary of Yakima River, courtesy Yakima County

A recent day on the Naches tributary of the Yakima River was like no fishing trip you’ve probably seen before. With a century-old dam being removed from the river, partners from a diverse coalition of stakeholders groups, resource agencies and the Yakama Nation gathered with a mission- save fish that could be left- almost literally- high and dry.

Nelson Dam was built in the 1920s, and refurbished in 1985, to divert irrigation water for Yakima and the Naches-Cowiche Irrigation Association for use by farmers and area residents. As is common for dams constructed at that time, the original dam was a major barrier to migrating fish.

Nelson Dam, photo courtesy Yakima County

“It has often been inhospitable for fall spawners like coho and nearly impossible for juvenile fish to pass upstream of the dam,” said WDFW habitat biologist Eric Bartrand. “They do have an old concrete fish ladder that did work to some degree, although never very satisfactorily.”

The dam also held back literally tons of sediment and silt, which has built up for miles behind the dam, and causes seasonal flooding of upstream communities.

After many years of discussion by a large number of groups and stakeholders on how to address the challenges presented by the dam, it is now being removed. Nelson Dam will be replaced with what’s known as a roughened channel, a man-made fish passage channel made out of a large rock to control the grade of the stream.

“The old concrete structure is coming out and they’re putting in a horseshoe-shaped boulder dam that has a very gentle slope where fish can work their way up and over,” said Bartrand.

The City of Yakima and Yakima County are the lead agencies on the dam removal, one of several public works projects meeting the Yakima Basin Integrated Plan goals. The Washington Department of Fish and Wildlife (WDFW) was a partner in developing that plan and plays an important role in the plan’s implementation.

WDFW’s role is making sure that fish in the river are taken care of. While pulling down a dam seems easy enough, you can’t do it without some groundwork in advance. In order for crews to take out the old structure and put a new one in, the river has to be “dewatered” in some areas.

Left: The dewatered portion of the river is shallow enough for workers to wade through but still deep enough for fish. Right: A small strip of land separates the dewatered portion from the free-flowing channel.

This involves bringing in giant fabric bags filled with sand, gravel and rocks and building a sort of temporary wall across parts of the river with them. While water can still flow through cracks between the bags and low spots, this wall reduces the amount of water that can move through the area. Instead, the water is redirected into channels that flow around the dewatered sections.

Next, WDFW staff and volunteers remove fish from the area so the water can be brought down to as low of a level as possible. Biologists from WDFW, U.S. Fish and Wildlife Service, Yakama Nation, Washington Water Trust, and Mid-Columbia Fisheries Enhancement Group all stepped up to help with this effort. It’s not easy to pull fish out of a couple feet of water, so electrofishing equipment was used. While it’s usually a bad idea to use electricity in water, in this case it was the best option.

Biologists divided into groups of four, one in each group wearing the electrofishing gear, which kind of resembles the backpacks used in Ghost Busters. The device sends electricity through a long wand into the water. The electrical current momentarily stuns fish. The biologists carrying nets catch the fish and put them in buckets. Because they are wearing waders, the biologists are protected from being shocked by the electricity.

The work is painstaking as each team works a quadrant of the area to make sure no section of the riverbed is missed.

The fish that are caught are released into the channels flowing around the dewatered area.

“We’re finding mostly sculpin,” said Bartrand. “We’re finding a fair number of lamprey in the sandy areas. We’ve gotten a few either resident rainbow trout or juvenile steelhead and a few juvenile chinook.”

That is good news regarding lamprey. The Yakama Nation has an effort underway to recover lamprey populations in the Yakima River. Lamprey are currently listed as a Species of Greatest Conservation Need (SGCN) in Washington State due to a decline in numbers from warming water temperatures. SGCN is applied to species whose populations are identified as being rare, declining, or vulnerable. Steelhead are also listed as a SGCN. There is a large-scale hatchery program trying to restore area steelhead populations as well.

Hopefully a new style of dam structure will help with that. As a win-win, it will ensure a more reliable supply of water to the area, provide more recreational opportunities on the river, reduce flooding, and help move needed gravel and sediment downstream for fish spawning areas for future generation of fish.

In addition, this project facilitates consolidation of other diversion dams and additional infrastructure downstream. That, in turn, frees up possibilities to restore Naches River floodplain as well as that of Cowiche Creek, which is currently productive for both coho and steelhead.



The Washington Department of Fish and Wildlife

The Washington Department of Fish and Wildlife is dedicated to preserving, protecting and perpetuating the state’s fish and wildlife resources.