There will be updates to Center Hill Water Control Manual

The U.S. Army Corps of Engineers (USACE) Nashville District completed an Environmental Assessment (EA), under the National Environmental Policy Act (NEPA), to update the Center Hill Dam (one of the 10 multipurpose projects that make up the Corps of Engineers’ system for development of the water resources of the Cumberland River Basin) and Reservoir Water Control Manual (the guiding document that specifies how the Corps of Engineers operates its reservoirs).

“As a major unit in the system, Center Hill Dam and Reservoir function to manage the waters on the Caney Fork River and contribute to the reduction of flood levels at municipal, industrial and agricultural areas along the Cumberland, lower Ohio and Mississippi Rivers,” according to a release by USACE. “In addition to the far-reaching effects of flood risk management, the project contributes to the electrical power supply of the area through the generation of clean, safe and efficient hydroelectric power. Power produced at Center Hill is sufficient to supply the needs of an average city of 125,000 people.”

As a result of this update, the Nashville District is implementing operational changes at Center Hill.

The EA evaluated eight action alternatives, which included analyzing a period of recorded data (1998-2022), new and rehabilitated structural features, watershed characteristics, communication networks, naming conventions, changes from previously approved EAs and modern forecasting methods. 

 “The manual was updated to capture changes in the basin over the last 20 years and to establish a new environmental and operational baseline following the completion of major structural repairs to the dam,” said USACE Nashville District Commander Lt. Col. Robert Green. “The selected alternative strikes a balance between all congressionally authorized project purposes. We appreciate the feedback and cooperation from the public and our partners, as their input was significant in making these updates.”

USACE selected Alternative 23 for implementation.

“A major change includes the minimum discharge from the dam. Alternative 23 strikes a balance between all project purposes, focusing on providing well oxygenated, continuous minimum flows during the typical low-flow season when they are most needed and switching to a pulsed minimum flow during the typical non-low flow season when water quality in the forebay generally exceeds state standards,” according to a release by the USACE.

The 48-hour pulse interval during the typical low-flow season helps preserve the ability for generation to meet peak demand during critical summer months. The pulsed minimum flow during the non-low flow season allows all water to pass through hydropower turbines, maximizing power generation while meeting all project purposes.

“All six project purposes were considered in determining the selected alternative. This ensures that hydropower demands will continue to be met while also revising recurrence intervals for minimum hydropower releases and allowing for a small volume of continuous discharge during the most critical months for the environment,” said USACE Nashville District Chief of Water Management Anthony Rodino.

The approved updated Water Control Manual is now in effect; however, no immediate changes to water management operations will be made until proper notice has been provided to the public. The current water management operations fall within the guidelines of the newly approved plan. As USACE begins to transition to the new operations laid out in the 2024 approved manual, the Nashville District will continue to operate as in previous years until 30 days past posting of public signs at access points along the Caney Fork or 01 June, whichever comes first. This will allow users to read and understand the changes prior to them being implemented. 

Center Hill Dam and Reservoir has six congressional authorizations:

  • Flood Risk Management
  • Hydropower
  • Fish and Wildlife
  • Recreation
  • Water Quality
  • Water Supply 

Flood Risk Management: Operations within the flood control pool were not changed during this update and USACE expects the project to continue to manage flood risk for the public as designed.

Hydropower: The selected alternative is not anticipated to impact the ability for Center Hill Dam to meet its congressionally authorized purpose for hydropower and would not result in significant adverse impacts to hydropower.

Fish & Wildlife: During the typical low-flow period, when releases from the dam are less frequent and typically of poorer water quality, the selected alternative will provide a steady stream of cool, oxygenated water that approximates the natural base-flow of the Caney Fork River. This will increase available habitat for aquatic species and is anticipated to benefit the trout fishery below Center Hill Dam.

Recreation: During the typical low-flow period, when releases from the dam are less frequent, the selected alternative will provide a steady stream of water that approximates the natural base-flow of the Caney Fork River. This increased flow will provide a greater width and depth for recreational opportunities and is anticipated to improve accessibility and reduce conflict points between paddlers and wading anglers. The change in ramp rates allows Center Hill to increase from one turbine generator in the first hour to three total units in the second hour. This may increase risk to waders and paddlers in the second hour of generation as compared to the existing operational practice. Public information sessions are planned to inform the public of the proposed changes and signage will be posted to help mitigate that risk. For the public’s awareness and for public planning purposes, water release plans are published on our website (below) for the next day. Release plans are subject to change based on changing conditions within the watershed.

Water Quality: The selected alternative provides improved water quality while balancing the requirements of other authorized project purposes. Continuous releases, typically through the orifice equipped sluice gate, during the typical low-flow season will provide a steady supply of well oxygenated water when water in the reservoir is typically below state standards.

Water Supply: The selected alternative is not anticipated to impact the ability for Center Hill Dam to meet the authorized purpose for water supply.

“The recreational community should be aware of these updates as planning is the first step in practicing good water safety. At times, downstream water levels may increase faster than before, but the typical daily peak stages will remain similar,” said Rodino. “Check the water release plan on our website the day before, have a plan in place to remain safe, wear an approved life jacket when boating or fishing, and above all be mindful that conditions could change.”

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Photo courtesy of U.S. Army Corps of Engineers Nashville District.

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