The Santee Cooper Project was responsible for forming the largest lakes in South Carolina – lakes Marion and Moultrie – which cover an impressive 160,000 acres. The lakes were designed to provide hydroelectric power to rural South Carolina, which they still do today. The dam system around the lakes is an integral part of the project, with the Santee Spillway helping control flooding from the impact of heavy rains.
Santee Cooper’s System Operations Department is responsible for ensuring lake levels do not exceed a maximum elevation of 76.8 feet, which is in accordance with our Federal Energy Regulatory Commission (FERC) license. The team also maintains the required discharges from Jefferies Hydroelectric Station, economically dispatches hydroelectric generation from St. Stephen Powerhouse and Jefferies, and maintains the minimum flows at the spillway.
When the Santee Cooper lakes receive direct rainfall or when inflows from lakes and rivers increase due to rainfall in the watershed, System Operations monitors the impact on our lakes, forecast the resulting lake elevations, and eventually spill if needed. Spilling is necessary to keep the lakes and dams from overtopping, which could erode and damage dams and cause more serious issues.
“Santee Cooper’s Lake Management application is updated daily with previous day actual data, including lake and river elevations, river flows, hydro discharges and spill rates,” said Manager of System Operations Planning Diana Scott. “The application is also updated daily with the Southeast River Forecast Center (SERFC) forecast data.”
All of this information is used to forecast lake elevations for discharge profiles to plan how much water will be used to produce energy and how much spilling may be required to ensure lake elevations are below the maximum elevation prescribed by FERC.
Controlled spilling operations minimize flooding because the discharges are limited to times when lake elevations may exceed safe levels. If these lakes did not exist, there would be no way to control the amount of water that reaches the flood-prone areas. Some property owners along the Santee River floodplain may experience minor flooding during spilling.
In 2024, we spilled a total of 1,163,987 cubic feet per second (CFS). The Santee Cooper Lakes are a wonderful asset to South Carolina and our System Operations team plays a vital role in maintaining it.