To prevent an outbreak of a deadly fish-killing disease, federal officials plan to begin tripling the amount of water flowing out of Lewiston Dam and into the Trinity River.

Starting Thursday, the amount of water coming out of Lewiston Dam will increase from 450 cubic-feet per second to about 1,300 cfs, according to the U.S. Bureau of Reclamation, which operates the dam.

The Trinity River flows into the Klamath River and the higher flows in the Trinity are meant to aid salmon and trout in the Klamath.

Federal officials and others are worried about an outbreak of a disease called ich, which spreads among fish crowded into slow-moving pools of warm water in the river. The higher flows from the Trinity are supposed to flush out the lower Klamath with cooler water and reduce crowding among the fish.

A small number of fish have become infected in “extremely warm water” in the Klamath, said Michael Belchik, a senior fisheries biologist for the Yurok Tribe, which is based on the Klamath River.

An ich outbreak in 2002 killed some 35,000 salmon and steelhead trout in the river.

“We take this threat to our fish very seriously, and we’re looking at every option to protect our fish,” said Thomas P. O’Rourke, Yurok Tribe chairman. “We don’t want to go through another catastrophe like the fish kill in 2002, and we will do anything we can to avoid that outcome this year.”

The Klamath Fish Health Assessment Team, which monitors fish fitness in the river, rated danger in the stream on Wednesday at “yellow” because of unfavorable physical and chemical conditions in the stream.

There are four “levels of readiness,” for the river, starting at green, the lowest level and best conditions for fish. Levels increase to yellow, orange and red, which means a fish kill is imminent or underway, according to the team’s website.

During the past several years of warm summer weather and drought, the higher releases from Lewiston Dam have been an annual event in August and September.

This year’s higher flows, which could go as high as 3,500 cfs, are expected to last until late September.

David Coxey, general manager of the Bella Vista Water District in Redding, said sending more water down the Trinity River means there will be less water for cities and agriculture in the Sacramento and San Joaquin valleys.

Nearly all the municipal water districts in the Redding area get water through the bureau.

“It’s disheartening how our supply reliability continues to erode,” Coxey said.

There is also less hydropower generated when more water is sent down the Trinity River, Coxey said.

Water is shipped via large pipes from Lewiston Lake to Whiskeytown Lake, where it is used to also generate power at the Carr Powerhouse. The water is then shipped by pipe again from Whiskeytown to Keswick Reservoir, where power is generated again at the Spring Creek Powerhouse.

Higher flows into the Trinity and Klamath rivers also ultimately mean less water flowing into the Sacramento River to aid endangered winter-run chinook salmon that spawn in the river in Redding, Coxey said.

“This is a discouraging decision that further hurts the salmon over here,” he said.