Southern Idaho reservoirs are heading into the winter with more water than average, but Paul Deveau doesn't want you to read too much into it.

The manager of the Boise Board of Control, which provides irrigation water to 164,000 acres through five irrigation districts across the Treasure Valley, worries that the relatively good news suggests farmers will have all they need next year. But U.S. Weather Service forecasters are already predicting a dry winter.

Even with below-average snowfall, river managers have a good chance to fill the reservoirs with next spring's runoff. But Deveau said that doesn't take him - and the people whose lives depend on how he manages his irrigation system - off the hook.

"It's still not good enough," Deveau said. "We have to have a steady snow melt. If it melts too quickly we go into flood control and we lose it."

Half-filled reservoirs in the fall are good news for Idaho Power Co., too, because they portend improved river flows through the company's hydroelectric plants up and down the Snake River. The utility expects to generate between 8 million and 8.5 million megawatt hours of electricity from its dams in 2009, compared to 6.9 million in 2008.

The more electricity Idaho Power generates from its hydroelectric dams, the less it must generate with coal or purchase at a higher price on the open market. So more water in reservoirs from Jackson Lake in Wyoming to Lucky Peak above Boise is generally good news for ratepayers.

But Jon Bowling, a water management engineer for Idaho Power, said winter snowfall and how federal dam managers release the water will determine how much the utility and its customers will benefit.

"What we hope for is they release for flood control throughout the winter instead of filling and spilling it in the spring," Bowling said.

Balancing the interests of Idaho Power and irrigation managers like Deveau falls to the U.S. Bureau of Reclamation and the U.S. Army Corps of Engineers. They also must consider the interest of boaters and fisheries, especially on the Snake and Payette rivers.

The Bureau of Reclamation controls most of the dozen-plus reservoirs on the Snake River and its tributaries, but the two agencies share in the management of the Boise system that includes Arrowrock, Anderson Ranch and Lake Lowell.

Lucky Peak was built primarily to control flooding and that's the main concern of the Corps of Engineers. The agency doesn't want to hurt Idaho Power or Idaho farmers, said spokeswoman Gina Baltrusch in Walla Walla, Wash. But lives and property take precedence over utility and farmer bottom lines.

"We operate for people protection," Baltrusch said. "We manage for flood risk reduction."

The corps and the bureau have what they call a "rule curve" - a collection of past histories of river levels through the season that guides how much space to keep open in Lucky Peak and other reservoirs to capture flood flows.

In early 1997, when warm weather and rain rapidly melted snow - called a rain-on-snow event - in the high country of Southwest Idaho, the Boise River reservoirs came within days of filling and flooding Boise and other low-lying areas. In spring 2006, high runoff flooded portions of Eagle Island.

These close calls underscore the need for residents along the river to own flood insurance, said Ryan Hedrick a hydrologist with the Bureau of Reclamation in Boise. The dams are not full protection against floods.

"One of these years we'll have a big flush, but who knows when? Hedrick said. "It will probably be a rain-on-snow event."

This winter's snowpack may be decided in the tropical Pacific Ocean. There, warmer currents are setting up what climatologists call El Nino conditions, which usually means warmer and drier weather for most of the Columbia River watershed, said Jay Breidenbach, National Weather Service hydrologist in Boise.

"It doesn't always work out that way, but if you average all the El Nino years, they turn out warmer but drier," Breidenbach said.

Still, it would take a very poor snowpack to keep the reservoirs from filling next spring because of the fall carryover.

Deveau takes all of the news into account. But like most irrigation managers, he is very conservative.

This year's carryover in the reservoirs comes, he said, from farmers and other users "scrimping and saving" every drop and he wants to ensure the water is managed wisely to pay off those conservation efforts.

"The weather people can't tell you what the weather will be tomorrow but I have to tell people what to plant, what loans to take out next year," he said. "Whatever we do or don't do may decide who makes it or not."

Rocky Barker: 377-6484