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Archive for Monday, October 24, 2011

Sediment creates issues in Kansas lakes, reservoirs

October 24, 2011

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— Dirt is slowly filling lakes and ponds in Kansas, and experts are divided over how much to worry.

The U.S. Army Corps of Engineers reports that there is still plenty of room for flood control, but some experts fear the influx of silt will threaten water supplies, The Wichita Eagle reported.

About 60 percent of Kansas residents currently get their water from lakes, and the number is expected to grow. To understand the issue, experts point to John Redmond Reservoir, which supplies water to several Kansas towns and the Wolf Creek nuclear plant. It has only about 58 percent of its original capacity.

“John Redmond is our poster child,” said Earl Lewis, Kansas Water Office assistant director. “It now has such a low average depth and has lost more than 40 percent of its storage area to sediment. If there’s one place in Kansas where we could (soon) have a problem with our water supply, it’s probably it. You wonder what would happen if we’d get a (long-term) drought like in the ‘50s.”

Long-term fixes are neither cheap nor quick. The cost of dredging a large reservoir could cost $1 billion. Building a new one would be even more costly and could take 20 years from initial planning to completion.

The Kansas Water Office, charged with long-term planning for future drinking water supplies, ranks the problem on par with the depletion of the Ogallala Aquifer because of its threat the long-term quality and quantity of our water.

“They’re going to fill up with their natural surroundings, soil and clay,” said Jerry de Noyelles, the deputy director of the Kansas Biological Survey, of the state’s lakes. “It’s nobody’s fault; nothing was done wrong. We have always known the lakes inherently weren’t going to last very long.”

Most of Kansas’ major reservoirs were built with 100-year lifespans. Many are now 50 to 60 years old.

Already there are issues. De Noyelles of the Kansas Biological Survey said there is “very significant connection” between blooms of blue-green algae and the increased sediment rates in many Kansas lakes. Toxins from the algae contaminate the water, causing treatment plants to spend more to produce clean drinking water.

But the Corps of Engineers isn’t panicking, noting that sedimentation rates were factored into the planning of all of their reservoirs.

Much of the current sediment has accumulated where it has little effect on the lake’s main uses, said Corps of Engineers hydrologist Stephen Spaulding. He noted that Perry Reservoir has about 15 feet of sediment in the lake’s main body, but there’s still about 50 feet of water in some places.

“We’re not going to worry about it. Who knows what regional needs will be in 20 to 30 years from now,” Spaulding said. “When that time comes, we’ll work with people to see if we can modify plans accordingly.”

Spaulding said one option is to simply increase what is considered a lake’s normal level a few feet, which could prolong a reservoir’s life 20 years. Most of the federal projects include huge areas of land around the lakes so the lake levels can be raised if needed.

“For all practical purposes it really doesn’t affect the actual operation at the lake,” Spaulding said. “As the pool gets higher, the space is increased dramatically, too.”

But that approach doesn’t necessarily work with nonfederal water supply lakes because they often are surrounded by houses and docks.

“Raise the water level a few feet in some places, like Gardner City Lake, and it will be in somebody’s living room,” de Noyelles said.

Rep. Tom Sloan, R-Lawrence, and Sen. Carolyn McGinn, R-Sedgwick, have been trying to push for solutions in Topeka for several years. They agree that the state needs to expand programs that decrease sedimentation by stabilizing soil along rivers and streams that drain into lakes.

But both said the state is headed in the wrong direction for such programs.

“The state water office has been very underfunded for the last four years,” McGinn said. “Some of the programs that really decrease sediment are some of the ones that are being cut.”

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