Sedimentation Challenges in Kansas ReservoirsPosted on Wednesday, January 18th, 2017 by Brad Schleeter
In Federal Services, Stormwater, tagged in
Reservoirs built by the Federal Government in Kansas in the 1950’s and 60’s were designed to fill with sediment. However, many are filling faster than expected, due to excessive streambank erosion, lake shore erosion, and agricultural runoff. This sedimentation reduces in-lake storage, fills in shallow lake coves, and covers the lake bottom in a layer of fine sediment, which impacts recreational usage, plant life, animal diversity, water quality, drinking water supply, irrigation storage, and more. At this year’s 5th Annual Governor’s Conference in Manhattan, presenters shared information on the sedimentation problems federal reservoirs in Kansas are facing. Below are two examples.
John Redmond Reservoir
Constructed in 1959, the John Redmond Reservoir is the primary water source for the Wolf Creek nuclear power plant. Currently, this reservoir has lost 40 percent of its storage volume due to sediment deposition. It is estimated that approximately 1,000,000 cubic yard (CY) per year or 620 acre-foot (ac-ft) per year of sediment is deposited in it.
The Kansas Water Office is committed to providing water for Wolf Creek with the John Redmond Reservoir through 2045. To this end, they led a dredging project over the summer of 2016. 3,000,000 CY of sediment was dredged from the reservoir, restoring 1,800 ac-ft of storage. This volume is equivalent to three years of average sediment deposition volume. At a total project cost of approximately $18M to $20M, the continuation of sediment dredging is likely not financially feasible based on the magnitude of the sedimentation issue.
The sediment dredging project was authorized through the Section 408 permit process, which allows a non-federal interest (the State of Kansas in this case) the ability to alter a U.S. Army Corps of Engineers project. The total length of the nine step Section 408 process is 32 months. As this was the first sediment dredging project of this magnitude in the state of Kansas, there were significant challenges during the permitting, including long lead time to start (1.5 years), sediment contamination concerns, and issues related to identifying and receiving approval for the disposed material.
Tuttle Creek Reservoir
Tuttle Creek was constructed in 1962. Approximately 40 percent or 176,000 ac-ft of its storage has been lost by sediment deposition. Using John Redmond Reservoir as a reference, the cost to dredge Tuttle Creek would be $1.8 Billion. This is not financially feasible, so lake managers are exploring other sediment removal options.
- Hydrosuction: To use hydrosuction, teams would install a syphon conduit to suck sediment from the reservoir bottom and discharge it downstream. This process has a vertical height limit of 28 feet, requiring the conduit to run through a dam structure, which could impact dam safety.
- Inlet Extension: This process involves the installation of flexible conduits over the existing 24-inch outlet openings and extending the conduit into the reservoir bottom to suck out sediment. It would require coring the conduit through the dam outlet works, which would be a challenge to gain approval.