Low Water Prompts BPAby CBB Staff
An operation at McNary Dam that the Bonneville Power Administration said at the Technical Management Team meeting last week would produce up to $5 million more in revenues from increased generation during the spring and summer was withdrawn this week.
The federal power marketing agency calculated that the falling water supply forecast and resulting lower than average river flows would produce almost no additional revenues with the proposed operation, which would allow the dam's turbines to operate outside the 1 percent peak efficiency range.
"Following last week's meeting, we re-evaluated the expected revenue gains based on the latest forecasts and found them to be very low," said Kim Fodrea of BPA. "So low, in fact, that they probably wouldn't cover the cost of the monitoring plan. We've decided not to press this any further this year."
The NOAA Fisheries 2000 biological opinion of the Federal Columbia River Power System's reasonable and prudent alternative (RPA) number 58 calls for turbines to be operated within the 1 percent peak efficiency range during spring and summer while juvenile salmon migrants are in the river. The operating limits were set as a result of studies in the 1980s that determined turbine efficiency and fish survival are directly related.
After re-evaluating those studies, BPA concluded that operating outside the 1 percent efficiency limit at McNary may not result in survival different than operating within the 1 percent limit, according to information provided last week by BPA.
If the dam can operate outside the 1 percent limit, it could spill less water and put more water through turbines to generate more electricity. Last week, BPA said that would gain the agency an additional $5 million per year in revenues in the spring and summer when the limits are in effect.
However, fishery managers say that putting more flow through the turbines decreases survival rates at the dam for yearling chinook and steelhead because about 3.6 percent more juvenile fish travel through turbines instead of over the dam's spillways. Current studies may be proving this out, fishery managers indicated this week, while the Corps said it is too soon to know for sure.
At this week's TMT meeting, Steve Haeseker of the U.S. Fish and Wildlife Service said studies now being conducted at McNary Dam, where the U.S. Army Corps of Engineers is testing the impact of turbine efficiency on juvenile salmon, is producing descaled fish when operating outside the 1 percent range. "There is a distinctive difference in the pattern of descaling," he said.
The Corps is conducting alternating tests at the dam, operating one generating unit at greater than 1 percent efficiency and then four units greater than 1 percent efficiency.
"The descaling rates are still very low," said Steve Smith of the Corps' Walla Walla District. "You need to be very careful where you go with this information."
"It's even worse news when just one unit is causing this," said Ron Boyce of the Oregon Department of Fish and Wildlife.
Fishery managers submitted a system operational request (SOR) in March after hearing that that BPA and the Corps were putting together a new monitoring plan to track the impact on juvenile salmon and steelhead survival when operating turbines at McNary Dam outside the 1 percent peak efficiency range. The SOR asked the river operating agencies to ensure that the BiOp operating limits are honored this year.
With the withdrawal by BPA of operating the dam beyond the 1 percent range, Cindy Henriksen of the Corps said the SOR is recommended, with the exception of those turbines now being tested.
Technical Management Team: www.nwd-wc.usace.army.mil/TMT/index.html
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