The Trinity River sees a dramatic spike in flow out of Lewiston Dam Tuesday and Wednesday.
The planned increase is part of the strategy of the multi-agency Trinity River Restoration Program.
The peak flow Tuesday and Wednesday is intended, among other things, to move around sediment for spawning fish and to cool down the Trinity River for migrating smolts, effectively approximating spring snowmelt runoff flowing into the river.
“Gravel supply from upstream of the dam is cut off, obviously,” said Ernie Clarke, a biologist with the US Fish and Wildlife Service. “So we’re trying to supplement what would naturally be coming down.”
He said this needs doing because, well, there hasn’t been much in the way of actual snowmelt.
The flow out of the dam has been increasing since April 22. It started out gradual — about 300 cubic feet per second. That number has risen greatly since the end of April, and today and tomorrow it will be at 8,500 cubic feet per second.
By May 18, the flow will have dropped to 2,000 cubic feet per second. Until July it will gradually fall to 450 — where it will stay until October, the start of a new water year.