NASHVILLE, Tenn. (June 30, 2022) – The system of dams and reservoirs in the Cumberland River Basin provide flood risk reduction, hydropower generation, navigation channels, and recreation benefits. It also provides a reliable water supply source for over 70 municipal and industrial users, as well as hundreds of private users.
The U.S. Army Corps of Engineers Nashville District allocates water storage for communities and industries surrounding large storage reservoirs at Center Hill Reservoir and J. Percy Priest Reservoir in Tennessee, and Laurel River Reservoir in Kentucky. Dale Hollow Reservoir in both Kentucky and Tennessee also provides water supply benefits.
Water supply is an increasingly important concern as communities plan for future growth. Over time, communities withdrawing water from nearby storage reservoirs grow and the demand for water increases. At the same time, there are competing purposes for water such as hydropower and recreation.
Ryan Wigner, hydrology and hydraulics technical lead for the U.S. Army Corps of Engineers Nashville District, said it is important to balance demands for water with the authorized purposes of the reservoirs to make smart informed decisions into the future.
When demands increase and additional storage is requested, the Corps of Engineers conducts updated water reallocation studies to assess the feasibility of reallocating additional storage. If approved, USACE facilitates new water storage agreements with water supply users.
“We need to ensure there is sufficient capacity in storage reservoirs for all the competing purposes so we can provide water storage to our stakeholders even in drought conditions,” Wigner said.
Amanda Burt, Nashville District’s Water Supply Program manager, said approved water supply users are required to pay an upfront cost of storage and are also responsible for a proportional share of annual operation, maintenance, repair, rehabilitation, and replacement costs at the project. These payments are made to the United States Treasury, not the Corps of Engineers.
Burt explained that dam and reservoir projects must have an approved reallocation report to reallocate storage space from an authorized purpose to water supply before the new or increased withdrawal is permitted.
“The report evaluates impacts to authorized purposes and ensures growth projections and need for water are reasonable, while also ensuring compliance with the National Environmental Policy Act” Burt said. “If approved, a certain amount of storage is then considered authorized for water supply, and users enter into water storage agreements and pay associated fees.”
At “Run of the River” projects like Cheatham, Old Hickory, and Cordell Hull in Tennessee, there is no long-term storage from which to reallocate for water supply. The authorized purposes at these projects are typically navigation and hydropower.
While a reallocation report is not required at these types of projects, the Corps of Engineers does conduct water availability studies at these projects to ensure authorized project purposes are not impacted by water supply withdrawals. Additionally, there may be fees for easements and other permits, but there are no fees associated with the water withdrawal when approved.
Nashville District storage reservoirs hold 7,461,023 acre feet of storage. This storage equates to more than 3.6 million Olympic swimming pools.
Wigner said managing the storage projects for water supply is important because there are so many demands for water, and because water is essential for life and economic activity.
“A reliable source of drinking water for the people and region we serve is vitally important,” Wigner added.
Nashville District’s Water Management Section manages the 10 dam projects in the Cumberland River Basin. Throughout the flood season of January to April, water is stored in the flood control storage projects – specifically Lake Cumberland, Center Hill Reservoir and Dale Hollow Reservoir. As long as these lakes are filled by early May, enough water is in storage to maintain minimum flows through the Cumberland River in Nashville for the remainder of the year, even if zero rainfall is observed.
This annual cycle at the storage reservoirs of filling and drawing down helps to maximize benefits for all authorized purposes. This includes more storage in the winter and spring, a larger surface area for the recreating public in the summer. The summer drawdown ensures a healthy flow in the river and supports water quality, fish and wildlife, navigation, and water supply.
Robert Dillingham, Water Management Section hydraulic engineer, explained that the stair-stepped layout of the mainstem navigation dams, the deep nature of the storage projects, and the location of water supply intakes ensure that water is available for withdrawal.
“Filling our storage reservoirs in spring towards a ‘summer pool’ ensures water is available in the summer and fall months as we draw down the storage reservoirs,” Dillingham said.
Congress did not include water supply as an originally authorized purpose at any dam project in the Cumberland River Basin. The Water Supply Act of 1958 provided the authority for the Corps of Engineers to reallocate storage space to municipal and industrial water supply.
(The public can obtain news, updates and information from the U.S. Army Corps of Engineers Nashville District on the district’s website at www.lrn.usace.army.mil, on Facebook at http://www.facebook.com/nashvillecorps and on Twitter at http://www.twitter.com/nashvillecorps.)