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Southern Idaho Sizzles by Dave Wilkins, Staff Writer Capital Press - July 12, 2002

Irrigation water supplies in Southern Idaho will be put to the test in the coming weeks, with near-record high temperatures in the forecast.

Daytime highs in the Boise area were expected to hit 105 degrees Fahrenheit late this week.

"There's an awful lot of evaporation when it gets that hot," said Roy Orr, manager of the Black Canyon Irrigation District in the Treasure Valley.

Black Canyon irrigators will be entirely dependent on reservoir storage water by the end of the week, Orr predicted.

"It's late enough in the year that we'll have ample water for irrigation, but we sure aren't going to have any carryover," he said. "Cascade Reservoir did finally fill, but Deadwood's not full and isn't going to fill."

Water managers will be watching carefully over the next few weeks with irrigation demands still near their peak. Farmers in Southern Idaho will be harvesting cereal grains this month, but Late-season crops like potatoes, sugarbeets and corn will need water for several more weeks.

Most water projects are expected to continue making deliveries through the end of the growing season, thanks in large part to a cold spring.

The cold weather prolonged the mountain snow melt and reduced demand for irrigation water during the early part of the season.

"It was cool in May, which really throttled back demand," said Vince Alberdi, general manager of the twin Falls Canal Co. in the Magic Valley.

The Twin Falls project began the year with a full allocation of five-eighths of a miner's inch to shareholders and has been able to stick with that. One miner's inch is equal to about nine gallons of water per minute per share.

There wasn't a much snow pack in the mountains of Eastern Idaho and Western Wyoming as farmers would have liked, but luckily, the biggest accumulation was in the higher elevations, Alberdi said.

High Snow Helped
The top-heavy snow distribution has allowed the project to pace its water supplies over an extended period of time.

"We could tell that the snow that we were looking at this winter was really high in the Tetons," Alberdi said.

When it first started to warm up in late spring and early summer, the snow up to 7,000 feet elevation provided the runoff. Later, water came from the larger accumulations at the higher elevations.

"That's what really gave us a natural flow for a longer time than usual this year," Alberdi said. "There has been a very nice drainage from the watershed this year, and that's what has given us the continuous natural flow."

But there could still be some longer-term concerns with spring flows into American Falls Reservoir lagging well behind the 20-year average, Alberdi said.

"The health of the aquifer continues to go down," he said.

The North Side Canal Co. in the Magic Valley actually increased its allocation to farmers from 60 percent to 80 percent on June 24 -- largely because of the cool spring and reduced irrigation demand in Eastern Idaho.

Good Timing
North Side irrigators started the year with a 60 percent allocation of just three-eighths of a miner's inch per share. The project was able to bump it up to a half-inch just as the weather really began to warm in late June, said general manager Ted Diehl.

"It came at a good time," Diehl said. "It looks like we should be able to run the rest of the year at 80 percent. In another three weeks we'll be over the hump with the grain gone. It won't be a big push."

Without the cold spring and reduced irrigation demand, the North Side would still be at a 60 percent allocation, Diehl said.

"We're still going to have to watch it carefully at 80 percent," he said. "There isn't going to be anything to waste."