Last year melting snowpacks have created a problem for the BPA when it coincided with strong winds in the northwest. As a result, the BPA avoided overloading the grid but was forced to give away surplus power to other utilities.
The BPA contends that spilling excess water over its dams to bypass hydro-generators is bad for the river environment. It says excessive spillage raises nitrogen levels in water, putting salmon and other fish in danger.
Last month, the BPA said it was looking at alternative contingency plans. However, in its Interim Environmental Despatch, it said it was prepared to put a temporary limit on wind as an "interim step".
In the event of an oversupply of power, coal, gas and thermal power plants would be the first to be limited.
However, curtailment impacts wind operators more than traditional power generators because a significant part of the income generated from a wind farm comes from tax and renewable-energy credits. These credits represent actual generation, so the less output from a wind farm, the fewer credits it accrues.
BPA administrator Steve Wright said: "We’re fortunate in the northwest to have extraordinary renewable hydropower and wind energy resources, but occasionally we have to adjust when nature gives us too much. Wind remains an important part of our clean energy future and is growing quickly. This is an interim step, which appears unavoidable at this point, to keep the power grid in balance while the region develops long-term solutions."
Speaking about the decision, AWEA CEO Denise Bode said: "BPA really ought to call this the ‘Anti-Environmental Redispatch,’ since it makes no sense environmentally and flies in the face of the agency’s obligation under the Northwest Power Act to promote renewable electricity in the region.
"Yet the agency chose to ignore its statutory duties and Obama administration policies, and instead to illegally promote its own narrow economic interest over meeting its contractual obligations with private renewable energy companies."