* BPA to reduce wind, nuclear output until June 15
* Spring storms boost streamflow on river system
* Spot power prices pressured by cheaper hydro supply
HOUSTON, June 10 (Reuters) - The Bonneville Power Administration (BPA) has curtailed nuclear and wind generation in the Pacific Northwest so that it can increase hydropower output as a way to protect migrating salmon and other fish, an agency spokeswoman said on Thursday.
Energy Northwest said its 1,131-megawatt Columbia nuclear power plant in Washington was reduced to 40 percent output from 55 percent earlier this week at Bonneville’s request.
A series of heavy spring rain storms moving across the region in recent weeks has increased streamflow on the Columbia and Snake river systems.
While the agency typically increases the amount of water it allows to spill over dams to help migrating fish, too much runoff increases the river’s nitrogen level which is bad for fish.
The Columbia nuclear plant and some Northwest wind farms are expected to remain curtailed until early next week when river conditions are expected to return to normal.
Daily power prices at the Mid-Columbia hub slumped to less that $10 per megawatt-hour this week, about half the typical price this time of year, as hydro output has risen. Off-peak power prices have traded in negative territory.
On Wednesday, dissolved gas levels at the Bonneville Dam reached levels that triggered action under federal rules.
BPA is now running as much water through its hydro turbines as possible to minimize the amount of water spilled to alleviate the danger of gas bubble disease for endangered fish. BPA is producing up to 24,000 megawatt-hours of hydropower a day.
Where possible, more water is being stored behind dams.
The agency is selling its surplus hydropower at low prices to encourage utilities to shut coal and natural gas plants, depressing daily power prices.
The need to keep hydropower output high also limits BPA’s flexibility to serve as a back-up for the region’s fluctuating wind power which has also been high due to the recent storms.
The Columbia reactor — which had been at 55 percent output since June 4 for work on the main condenser — is not expected to begin increasing its output until Tuesday morning even though condenser work is scheduled to be finished Friday, BPA said.
Current high river conditions aren’t expected to last much longer.
In its latest forecast, the U.S. Northwest River Forecast Center projected water runoff at The Dalles Dam on the Columbia River climbed to 69 percent percent of normal for January-July from 66 percent in its previous forecast.
But that’s well below last year when The Dalles actual runoff was 84 percent of the 30-year normal.
The Dalles is a key point to measure the volume of water available for power generation in the Northwest, which receives about 65 percent of its power from hydroelectric dams. (Reporting by Eileen O’Grady; editing by Carol Bishopric)