#Runoff news: South Platte River running high

From The Sterling Journal-Advocate (Jeff Rice):

Higher-than-usual snowpack in the Colorado high country and a relatively wet May have irrigation reservoirs filled to the brim and ditch companies running full blast. The conditions also illustrate the need for more water storage in the South Platte River basin.

The Colorado Division of Water Resources’ May report won’t be out for another day or so, but the April report already showed reservoirs nearly brimming. A month ago the North Sterling Reservoir was at 95 percent capacity and Prewitt was at 86 percent. Jim Yahn, manager of the North Sterling Irrigation District and Prewitt Reservoir, said Tuesday both reservoirs are full…

According to the SNOTEL report, the May 30 reading showed that the snowpack contained slightly more than 10 inches of water equivalent. The peak this year was in the first week in April with about 16 inches of water. The beginning of snowmelt season had brought that down to under 10 inches in early May before a late winter blast two weeks ago boosted the snowpack some.

While the news seems good for this year – rainfall in the upper basin areas, especially in the Denver metroplex, swelled the South Platte to a little more than 3,000 cubic feet per second, while snowmelt has maintained that level – it underscores the need for additional water storage in the basin.

Frank pointed out that the South Platte River Storage Survey is under way and researchers are looking for places to put more water when it’s available, as it is this year.

“Since 2009, almost every year, we would have been able to store some water,” Frank said.

But if the high-level solution is easy, the practical aspects make it a much more complicated issue. For one thing, although on-stream storage – that is a dam across the South Platte – isn’t out of the question, it’s probably not a near-term solution.

“If we could dam the river, we probably could store 300,000 acre feet of water a year in times like this,” Frank said. “But the permitting process, with the environmental impacts and the economic considerations, are much, much longer than off-stream storage.”

And the off-stream sites that could be gravity fed already have been or are being developed, he said. That leaves pumping water out of the river “uphill” to a basin for storage. And that, Frank said, opens up another set of questions.

“Right now you probably could pump 2,000 cubic feet per second out of the river, but how often would you use that size of a pump?” he asked. “Even if you just pumped 500 cubic feet per second, you could pump 1,000 acre feet a day. The North Sterling holds 75,000 acre feet, so it would take 75 days of pumping at that rate just to fill a reservoir the size of North Sterling. This water that’s going past us, it’s not going to last 75 days. We have maybe two or three weeks.”

What makes more sense, Frank said, would be a series of pumps filling a series of smaller basins. And there’s still the question of where to locate the reservoirs.

“It’s all about location, optimization, where the demand is … it gets really complicated,” he said.

The storage study is supposed to be completed in November and will look at a variety of storage methods and will suggest a handful of sites that could be developed.

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