Erica Terence, conservation and executive director of Orleans-based Klamath Riverkeeper, said the dam blocks 20 percent of traditional Shasta-run coho salmon spawning habitat.

"We really want the water conservation district to find a way to operate that will meet the biological needs of these coho salmon," Terence said.

That may mean the earthen dam needs to come down or the Montague Water Conservation District can come up with an alternative solution, such as building a fish passage around the dam or other habitat improvements, to ensure coho get to their native spawning grounds, Terence said.

Supervisor Michael Kobseff said another protracted fight over removing a dam is not something the county needs.

"It would be devastating," he said. "Let's face it."

Kobseff is among those fighting an ongoing push to have four dams removed farther upstream on the Klamath River. The Shasta and its sister river, the Scott, feed into the Klamath below those dams.

He said the community of Lake Shastina, north of Weed, has grown to nearly 1,200 homes in what's been one of the fastest-growing areas of the county. The lake also is a popular boating, swimming and fishing spot, particularly in the spring and early summer.

He said just the threat of the lake's demise will cause home values to tank, similar to the way prices have plummeted near Copco Lake, one of the reservoirs dammed on the Klamath.

"This is déjà vu," he said.

Terence acknowledged the lawsuit won't be popular with homeowners in the area.

The reservoir helps supply water for Montague, a town of about 1,400 people east of Yreka.

Farmers and ranchers in the area also use water diverted from the reservoir, which holds back part of Parks Creek, a Shasta River tributary.

Terence said the notice, filed Monday, gives the district 60 days to come up with a solution out of court before an official suit is filed.

A district spokeswoman said Monday no one was available to comment but she said the district's board's regular meeting is today, and the topic will be addressed.

Coho salmon on the Shasta and the Scott rivers are listed as threatened under the state and federal endangered species acts.

Klamath Riverkeeper is one of a number of groups — including commercial and recreational fishing organizations and Klamath River Indian tribes — that have sued to challenge irrigation practices along the streams.

The lawsuits and government officials' attempts to regulate farmers' water use have caused a political backlash in Siskiyou County. Farmers and their political allies say the groups are threatening their livelihoods in one of the few industries economically struggling Siskiyou County has left.

But Terence says she's striving for a solution that will benefit farmers and fishermen, while keeping fish populations healthy.

Terence said the canal filled from Lake Shastina often has more water than the river in dry months, so much so she's heard stories of locals swimming in the canals during the summer.