The National Marine Fisheries Service (NMFS) has concluded that removal of Condit dam on the White Salmon river in Washington state, US, would greatly improve conditions for the river's threatened chinook salmon and steelhead runs in the long run despite negative short-term impacts.
In a long-awaited biological opinion released this week, federal fish managers said that failure to take out the 38.1m high dam would result in long-term decline of the fish stocks and could even drive runs to extinction. Taking out the dam would open 53km of native steelhead habitat above the dam and 23km of habitat for spring chinook salmon.
Biologists said it would restore natural river processes, such as the transport of spawning gravel and large woody debris, and lower the water temperature in the reach downstream from the dam. As long as the dam remains, the biological opinion said, it will continue to block the formation of pools and riffles and the deposit of gravel, depriving adult fish of important resting and spawning habitat and reducing rearing habitat for juvenile fish migrating downstream.
If the Federal Energy Regulatory Commission permits the dam’s destruction, Condit would become the tallest dam ever dismantled in the US. The findings are good news for PacifiCorp, the Portland-based utility that owns the 93-year-old structure. PacifiCorp hopes to remove the dam in October 2008 at a cost of US$20M.