PIERRE — After years of drought, folks downstream from the Lake Oahe reservoir are bracing for another possible water problem in 2010.

Too much water.

Some area residents and city officials are worried that a large spring runoff will pour in to Oahe, boosting water levels that already are at their highest point in a decade.

This graph shows the average December elevation in Lake Oahe (blue bars) and the average December discharge from Lake Oahe (red line) since 1996. The 2009 figure for elevation is for the month so far; the 2009 figure for discharge is an average of the planned discharge over the next three weeks. Advertisement

This is a boon for power generation at Oahe Dam, but the possibility of levels rising even higher has people like Brad Lawrence concerned.

“They are gambling that they aren’t going to have a large plains runoff,” said Lawrence, public works director for the city of Fort Pierre. “They are gambling with flooding us.”

Oahe Project administrator John Bartel said those concerns are premature.

“Right now, the pool level is exactly where we like to have it right now,” Bartel said. “An enormous amount of moisture in the upper Missouri basin would have to accumulate before we would start sounding an alarm.”

Lake Oahe is currently 1,607.8 feet above sea level. That’s 10 feet above the average December level for Lake Oahe — and three feet below the highest recorded December level, recorded in 1997 three months before Pierre residents had to build levees along the Missouri to guard against possible flooding.

“We did some preventative measures where we did some sandbagging on the shore,” Bartel said. “That’s not even in the picture right now, because we just don’t know how much moisture’s going to fall.”

State climatologist Dennis Todey said it’s too early to say how much snow will fall in the upper Missouri basin.

“The biggest part of winter precipitation comes in the late winter, in February and March,” Todey said. “We would have to wait until that point to see what kind of snowpack we’re looking at. Currently we’re not looking at any astounding snowpacks.”

Lake Oahe can hold water up to 1,620 feet above sea level. The closest it has ever gotten is 1,618.2 feet above sea level, recorded in 1997.

Currently discharge from Lake Oahe is averaging around 20,000 cubic feet per second, significantly below averages in past Decembers. But despite the lower discharge levels, input is even lower. The lake level is expected to drop half a foot between now and Jan. 8.

For Pierre resident Larry Weiss, a retired engineer, the situation today is reminiscent of 1997.

“I do remember in ’97, we had the same concern and raised the issue with reservoir control of why not lower the elevation prior to spring runoff,” said Weiss, a former member of the city commission. “A little more safety factor would be good — but we’ve got three months of winter left when the reservoir could be lowered.”

Lawrence also believes the Corps should be discharging more water.

“They could have discharged all fall,” he said. “The risk they are creating is a flood risk for the Pierre-Fort Pierre area, and I think that’s an undue risk.”

Bartel said the lake’s level is exactly where the Corps wants it.

“The lake levels are right where they’re supposed to be,” Bartel said. “There’s no perceived dangers out there that we know of.”

If increased snowfall leads to an expectation of a large spring runoff, Bartel said the Corps would revisit its predictions and might discharge more water.

In the meantime, Bartel said the Corps is taking advantage of the high water level to generate electricity. The dam is currently producing power at 95 percent of its capacity — up from 70 percent of its capacity in 2006 when the lake was 40 feet lower.