LEWISTON, Idaho — The Army Corps of Engineers has reduced water flows from a northern Idaho dam to decrease dissolved gas levels that can affect juvenile fish.
The water flows exiting the Dworshak Dam were reduced Monday and will remain low for a week as nearby hatcheries release salmon and steelhead trout, the Lewiston Tribune reported .
The water that plunges hundreds of feet from the dam’s spillway into the north fork of the Clearwater River creates high levels of dissolved gas. More water has been released through the spillway recently because one of the dam’s turbines is down for repairs.
High levels of dissolved gas can harm fish in the river and at the Dworshak Hatchery, which draws its water from the river, Adam Izbicki said, the hatchery’s assistant manager.
“Although the total dissolved gas levels we are experiencing in the hatchery are not lethal, they are higher than desired and do cause some fish health issues,” Izbicki said.
The Clearwater Hatchery draws water from the reservoir, but its fish are affected by the high gas levels when they’re released.
The fish will be released directly into the Clearwater River instead of its north fork in an effort to shield the fish from high gas levels, Izbicki said.
The corps typically releases high-volume flows in the spring as snowpack runoff begins to fill the Dworshak Reservoir.
The larger releases will likely resume next week, Steve Hall said, corps water manager at Walla Walla. The reservoir’s elevation will likely be lowered by mid-April to capture the runoff, which will raise the elevation by several feet, he said.
“So we will have to turn up the discharge, but there will be less impacts from that because most of the fish will have been released from the hatcheries,” Hall said.
The dam and reservoir are about 50 miles (80 kilometers) east of Lewiston.
Information from: Lewiston Tribune, http://www.lmtribune.com