Columbia/Snake river hydro controllers learned a not-so-hard lesson recently when an unanticipated boost in wind power into the transmission system forced increased spill, which boosts total dissolved gas that can be harmful to migrating juvenile salmon.

The incident was brief, a five-hour period that began at 7 p.m. June 30, according to Scott Simms of the Bonneville Power Administration. The Columbia and Snake rivers were swollen, with eight federal dams passing water by generating as much power as could be sold and/or transmitted and via involuntary spill (beyond spill prescribed specifically for salmon and steelhead downstream passage).

The generation scheduled each day to meet demand includes input from a fast-growing wind generation industry, whose windmills were speeded that day because of stronger-than-expected breezes.

Operators were forced for that time period to "throttle back the hydro system" – reduce generation to allow the system to absorb the wind power -- and increase spill to assure the system remained in balance, Simms said. Bonneville markets the power generated in the system, scheduling power inputs and outputs.

Water flushed through spill gates plunges into the water far below, entraining air and increasing the downstream concentrations of dissolved gases. Water rushing through the turbines creates little gas. Excess dissolved-gas concentrations can have adverse effects on freshwater aquatic life.

State imposed TDG caps are 115 percent in the forebay and 120 percent in the tailrace.

The need June 30 to reduce hydro generation by from 300 to 500 megawatts pushed up TDG, but not beyond the 120 percent – a threshold where effects on fish begin to become more pronounced, Simms said.

"The good news is there were no (system) reliability impacts and there were no fish impacts," Simms said.

The high wind-high water scenario was anticipated in a Northwest Wind Integration Action Plan developed cooperatively by BPA, the Northwest Power and Conservation Council and others.

"With increasing amounts of wind, there will likely be times when large, unexpected changes in wind output (so-called 'ramping events') coincide with periods of limited hydro flexibility," the 2007 plan says. "Initial analyses indicate that these will be low probability events, but if other sources of flexibility are not available at the same time, system operators will need to limit wind output for brief periods in order to maintain reliability."

But the response to last week's first-time event involved some glitches.

"We had a bit of a communication problem," Simms said.

Wind power sources, 10 in all, are required to "schedule" their planned input into the system. They are allowed to "deviate" from their schedule – send more or less power -- if the system can handle it.

As the high water-upward wind deviation situation loomed, BPA began "calling wind generators to tell them they had to hold to their schedules," Simms said. One did feather back its power generation. Two or three others were contacted but somehow the message did not get across, Simms said. BPA could not reach the other wind generators that evening.

The situation revealed a need to strengthen the procedure. BPA must make sure its directions are clear, and understood, in such instances. That will happen, Simms said.

The wind generators also must maintain a 24-hour a day, seven day per week point of contact, something that had already been expected of them, Simms said.

"We learned from this experience on both sides," he said.

The incident was for the most part a hiccup in what has been a long-running balancing act. A cool spring resulted in a delayed start to the runoff into the Columbia, Snake and their tributaries. When the meltdown was fully triggered in May, an average snowpack has released water over a condensed timeframe.

"We've just recently gotten the flows to the point where we weren't spilling involuntarily," said Jim Adams of the Corps, which along with the Bureau of Reclamation operations the dams in the system. Spill has generally been since mid-May above levels called for NOAA Fisheries' biological opinion on Federal Columbia River Power System operations. Turbines have also been turning at full capacity.

"When it did come off (the runoff) it came all at once," Adams said.

The wind power industry is amidst a surge. It began in 1998 with a 25-megawatt facility coming online. Now the system brings in about 1,500 megawatts an another 2,000 megawatts is expected to be added by 2009, Simms said.