Water releases from central Idaho's Dworshak Dam were ratcheted down to some degree Wednesday evening as fish and hydro system managers tried to strike a balance between providing flow augmentation now for migrating juvenile steelhead and salmon and assuring a maximum store of water to help returning adult fish this summer.

Normally mountain runoff would be gushing into the reservoir at this time of year, giving managers more certainty about the amount of water they'll have to deal with.

But stubbornly cemented snowpacks have made it difficult to decide how much water can be released from behind Dworshak while having certainty that the reservoir can be refilled. The reservoir's cool water is an important tool later in the season to lower water temperatures in the Snake River for summer fish migrants.

The U.S. Army Corps of Engineers through April ran Dworshak's powerhouse at full capacity, about 10,500 cubic feet per second going out of the reservoir while about half of that volume was coming in.

That dropped the reservoir elevation by nearly 40 feet, clearing space to assure flood control capability during the peak of the spring freshet and, putting additional water in the Snake for migrating spring chinook salmon and steelhead. The dam is located on the North Fork of the Clearwater, which pours into the Clearwater and then the lower Snake River.

Salmon managers during a Wednesday meeting of the Technical Advisory Committee wanted to take a wait-and-see approach, continuing the 10.5 kcfs flows for another week before deciding on future operations. That recommendation was based on the rapidly increasing number of juvenile fish that have launched their downstream migration.

"The fish are in the river and moving," said NOAA Fisheries' Paul Wagner. He noted that the chinook smolt passage index had climbed to 163,000 estimated passing the lower Snake's Lower Granite Dam Tuesday and 1.2 million to-date. The steelhead index totaled 1.3 million.

The Corps, which operates the dam, wanted to implement a stair-step reduction in outflows rather then continuing the higher flows and, potentially, being forced to drop suddenly to minimum outflows, 1.3 kcfs, to assure refill.

"The Corps is getting much more concerned about the risk of refilling," said the agency's Jim Adams, who acknowledged that that risk is low given falling, but still above average, forecasts of snowpack runoff. The reservoir elevation had dropped to 1,475. Reaching full pool, 1,600 feet, by the Fourth of July is the target.

The Corps' forecast pegs April-July runoff into the reservoir at 3 maf, which would be 112 percent of normal. Its forecast for May-July is 2.68 kaf, 135 percent of normal. A Northwest River Forecast Center forecast released Wednesday says the most likely scenario is runoff of 2.93 maf from April through July, 111 percent of average.

Signs of the spring meltdown beginning have only appeared recently. Inflows rose from 9 kcfs May 3 to 16.1 kcfs Wednesday.

The Corps proposed dropping outflows to 7.5 kcfs Wednesday night, then to 5.5 Sunday night. The next step, pending a TMT evaluation of the situation next week, would be to drop to minimum outflows May 16.

"By then, we expect flows to be up everywhere," Adams said of other Snake tributary snowpacks that would be released if a forecast higher temperatures materialize.

Wagner and Russ Kiefer of the Idaho Department of Fish and Game argued that higher outflows now would provide benefits now for the building salmon outmigration and maintain needed space in the reservoir to avoid higher volume release during the peak of the spring freshet.

"When it comes off it's going to come off fast," Wagner said. That could force involuntary spill at dams downstream such as Lower Granite, which would create total dissolved gas levels that are unhealthy for fish.

Salmon managers ultimately went along with the Corps operational plan.