KU News Release

KU researchers say Kansas lakes are filling in and shrinking

LAWRENCE — Water reservoirs across Kansas are shrinking, leading to taste and odor problems in drinking water for some communities, according to a research program at the Kansas Biological Survey at the University of Kansas. Even more, the cost to remedy the problem could reach millions of dollars.

“Our lakes are filling in,” said Mark Jakubauskas, research associate professor at the biological survey and team leader for the Applied Science and Technology for Reservoir Assessment Initiative. “The north end of Perry Lake, for instance, has lost about a thousand acres over the past 30 years. That’s lakefront property that’s been lost. It’s trees, grass and wetlands now.”

Jakubauskas said the sedimentation is caused in part by soil erosion from farmlands and watersheds that flow downstream and collect at the floor of the reservoir.

That shallow water not only lowers the reservoir’s water storage capacity but also promotes the growth of blue-green algae, which diminishes the quality of the drinking water.

“Many reservoirs in Kansas have experienced some level of taste and odor problem,” he said.

Jakubauskas said to gain more information on the lakes, the biological survey invested in a high-tech echosounding system to measure the depth, or “bathymetry,” of lakes in Kansas.

Just like the sonar technology used by the military, the system sends a sound wave from the surface of the lake to its bottom, measuring the time it takes for the wave to return. Because researchers know how fast sound travels through water, they can calculate the depth of the lake. A short time means a shallow lake.

“With our system, we can take 40,000 depth measurements of a 200-acre lake in about two hours,” he said. “That’s 40,000 points that tell us how deep it is, so we can make extremely detailed maps of the lake bottom.”

Using this technology, Jakubauskas said, researchers can also measure the thickness of the sediment, or the distance from the present-day bottom of the lake to the old bottom when the area was first flooded.

Jakubauskas said many Kansas lakes are silting more rapidly than expected. Cheney Reservoir, for example, is 27 percent filled in. Mission Lake in Brown County has lost 50 percent of its volume since its construction in 1924.

Their research has showed them that Gardner Lake in Johnson County has become so shallow in its upper end that it is now only a few feet deep.

Thus far, the biological survey has collected information on the depth, water quality, sedimentation and storage capacity of five lakes: Olathe, Carbondale, Gardner, Lone Star and Dabinawa.

Under a contract from the Kansas Water Office, the project is expanding to return to Olathe Lake for better information and to include Wabaunsee Lake and John Redmond Lake in Coffey County.

Jakubauskas said the research is especially useful for some smaller communities that depend on these lakes for recreation, drinking water and flood control.

“These people don’t have the deep pockets to go out and do surveys,” he said. “They’re going to be among the first affected because their lakes are small, they affect a small population and they don’t have a lot of money to rehabilitate these lakes.”

He said the biological survey can not only assess the condition of lakes for those communities but also estimate the amount of sediment that might need to be dredged to rehabilitate the lake.

Jakubauskas said before this research, state and local governments and agencies had little information on the state lakes, such as how much drinking water they hold or how long that water will last. This information is especially critical during this drought year.

His team also uses a boat-mounted coring machine with a hollow tube to remove a core of sediment from the reservoir to measure the sediment depth and to learn what kind of sediment it holds and whether it’s rocky, silty or sandy. The type of sediment determines to how expensive the dredging process might be.

For example, to remove 91.5 million cubic yards of sedimentation from Perry Lake could cost up to $457.5 million.

Jakubauskas said the information is especially of use to the Kansas Water Office, the State Conservation Commission, the Kansas Department of Wildlife and Parks, the Kansas Department of Health and Environment and the U.S. Army Corps of Engineers.

The research is also being used in some environmental studies classes at KU, where students are interpreting and analyzing the data.

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