Earlier we asked readers to pose questions they would like us to address in Balancing the Basin. One reader asked why Richard B. Russell Lake varies little in its level and if it could be used to protect the levels of the other two reservoirs. We get this question from time-to-time, especially during a drought when the levels of Hartwell Lake and Thurmond Lake decline.
The short answer to these questions: Planners designed Russell Lake to operate within a limited range, and that range was defined by Congress as our conservation storage allotment. Allowing it drop more than 5 feet below full pool can impact the efficiency of the turbines, but it also violates operating parameters that can only be chanced by congressional authorization.
The longer explanation: All three reservoirs have multiple purposes – hydropower production, downstream navigation, water supply, water quality, recreation, and fish and wildlife management. Hartwell and Thurmond have another, vital, purpose of flood risk reduction (originally called ‘flood control) that Russell Lake does not have. Instead, hydropower production sits at the top of the mission list for Russell Lake.
Congressional authorization and the design of the Russell Dam only allows for a 5-foot fluctuation above and below full pool of 475 feet above mean sea level (ft-msl). At levels above 480 ft-msl we endanger the dam’s integrity. At levels below 470 ft-msl we fall outside our authorized operating range and begin to lose turbine efficiency. But there is good news.
Russell Lake has eight power-generating turbines. Four of the turbines also have pump-back capabilities. They can run in reverse at night to draw water out of Thurmond Lake back into Russell Lake. This water can then be used over-and-over to generate low-cost, non-polluting energy. This saves water in the other two reservoirs while still allowing us to meet peak power demands in hot summer afternoons or cold winter mornings. For a visual explanation, please visit our You Tube channel at http://bit.ly/1kwtzkS.
Pumping water back into Russell Lake does cost money. When we pump water back the government must purchase commercial power to run the turbines in reverse. We do this at night when commercial power rates are lowest so we can have the water available during the days when demand peaks
Because of its relative small size, Russell contributes little to downstream water needs for the Savannah River basin. We must still rely on Thurmond and Hartwell lakes to meet those needs. That doesn’t mean we don’t draw from Russell during severe droughts. We have used its limited conservation pool to assist with downstream needs, but it is not a main source of water
By using Russell’s pump-back capabilities we can still provide much of the peak power demands during dry periods while mitigating water loss from the reservoir system. This helps protect reservoir levels at Hartwell and Thurmond while still providing power to homes and businesses throughout the southeast.
~ Billy Birdwell, Senior Public Affairs Specialist