Lakes in Kansas
Water reservoirs and lakes across Kansas are shrinking, leading to taste and odor problems in drinking water for some communities, according to a survey done by the University of Kansas. Even more, the cost to remedy the problem could reach millions of dollars.
The north end of Perry Lake has lost about a thousand acres over the past 30 years. Lakefront property has been lost. 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. 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.
Using this technology, 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. 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.
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. 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.
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 droughts.
The 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 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 $458 million.
December 14, 2006 6:47 AM | Category: Lake