By Tracy Robillard, Public Affairs Specialist
Thanks to above-average rainfall in both the Hartwell and Thurmond sub-basins during the month of April, coupled with consistent rainfall during the winter months, the Savannah River Basin has climbed into drought level 1 status.
The Hartwell sub-basin received 5.3 inches of rain this April, exceeding the April average of 4.59 inches. The Thurmond sub-basin received 4.91 inches of rain, exceeding the April average of 3.54 inches. The Russell sub-basin also received above-average rain, with an observed 4.22 inches compared to the average of 3.55.
Most of this rainfall came in the last few days of the month. Thurmond received 2.33 inches of rain in just three days, April 27 – 29. Hartwell received 2.36 inches in the last four days of the month.
Since the soils have remained saturated from consistent winter and spring rains, this April rainfall produced greater inflow to the reservoirs, providing significant aid to their recovery.
This was the wettest April in the Savannah River Basin since 2003. That April, Hartwell received 6.42 inches, Russell received 4.83 inches, and Thurmond received 5.25 inches of rainfall.
Drought Level 1
The basin officially reached drought level 1 status on May 5 when the Thurmond reservoir climbed to 326 ft-msl. Under the Corps of Engineers drought plan, water managers operate the basin at the specified drought level until the pools rise at least two feet above that trigger level elevation. The Thurmond pool was in drought level 2 since February but has gradually climbed past the level 2 elevation trigger of 324 ft-msl.
This means the minimum outflows from the reservoir system will increase. Under Drought Level 1 operations, minimum releases at the Thurmond Dam are 4,200 cfs if the Broad River is flowing greater than 10 percent of the 28-day average flow rate. As of this writing the Broad River is flowing in the 53rd percentile. The minimum outflows are further reduced to 4,000 cfs if the Broad River is flowing at or below the 10 percent mark. Read more in our recent post “How the Broad River Influences Outflows.”
We anticipate the reservoirs to climb out of drought status very soon and will update stakeholders via Balancing the Basin. We welcome your questions and comments.