Officials say this looks to be one of the driest years on record, and if it is, there may not be much water left to help salmon migrate to the ocean, especially because the fish are forced to compete with irrigators' needs. Twin Falls-area authorities wanted salmon water releases to start sooner than Thursday, but the federal government did not want the water from the upper Snake to reach Lower Granite Dam until July 1, said Kim Fodrea, hydraulic engineer with the bureau's Portland office. Beginning the flow now and increasing it to 1,500 cfs would get the water to Lower Granite just in time for salmon on their way to the ocean. The dense plumes of vegetation are back, despite having dissipated since the early 1990s. The mats in the past covered parts of the Middle Snake, and their presence sparked efforts to reduce the amount of pollutants dumped into the river.
Officials say low water, high temperatures and longer days also help form the algae.
McMasters said it will take solid flows of water to help wash the mats away. But that may not be easy since this year's below average snowpack means water managers limited flows from reservoirs on the upper Snake, keeping the river for the past several weeks at the minimum level of just above the 260 cfs. That is the flow required by Idaho Power Co.'s federal power license for the Milner Dam power plant.