International Dredging Review

International Dredging Review
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Milford Lake like most large multi-use reservoirs across the world is filling up with sediment.  This is no surprise. Reservoir sediment accumulation was always anticipated but concern is growing that in coming decades this reservoir like so many others will be unable to meet its original purposes. To make matters worse Mil-ford Lake experiences frequent severe harmful blue-green algae blooms that render part or all of the reservoir totally unusable for recreation.  All the while the lack of sediment in the down-stream Kansas River is degrading the bed and impairing habitat for turbidity-dependent species.

The fact is reservoirs across the world are experiencing impacts due to sediment accumulation.  In the United States most large dams were built with storage specifically allocated for sediment accumulation over an economic life of 50 to 100 years. The average age of these dams is around 30 years with over half having exceeded 50 years meaning that impacts from sediment accumulation if they haven’t been experienced already are just around the corner. The current strategy of trapping sediment in the reservoir and storing it there indefinitely is not sustain-able.  In the short term this “trap and store” approach leads to dramatic increases in operations and maintenance costs associated with clogged inlets turbine abrasion silted-in boat ramps and docks harmful algae blooms and other sedimentation problems.  In the long-term it causes the complete loss of all reservoir benefits.

To address this issue the U.S. Army Corps of Engineers and State of Kansas held a two-day workshop on July 20 and 21 2016) in Manhattan Kansas on reservoir sediment management options with a specific focus on Milford Lake. This workshop was sponsored by the Corps Regional Sediment Management Program a program that is trying to help the nation manage sediment more intelligently. Thirty-seven people attended from 13 state and federal agencies to learn about ways to manage reservoir sediments. Drs. John Shelley Corps of Engineers Kansas City District and Paul Boyd Corps of Engineers Omaha District educated participants using real-world examples on low-cost options for passing sediment through or around dams. These methods include reallocation new reservoirs dam raises dredging sediment yield reduction sediment bypass sediment sluicing drawdown flushing pressure flushing density current venting hydrosuction and inlet extension. Participants also “got their hands dirty” while gaining appreciation for how these methods work using small-scale bucket-and-sand demonstrations created by Joel Monnig a senior in Engineering Technology at the University of Central Missouri.

Bryan Young from the University of Kansas found the workshop “information packed and highly relevant.” Tom Stiles Kansas Department of Health and Environment remarked that the workshop featured a “very good presentation of information” and a “good mix of participants.”  Another participant concluded “I thought I had a firm understanding of reservoir sedimentation but this workshop opened my eyes to many layers of the issue.”

Reservoir sedimentation is not going away. Education and collaboration like that started in this workshop is an essential step in solving this problem.