January brought less than average rainfall at all three upper basin reservoirs with the largest rain deficit recorded at Hartwell sub-basin. Hartwell fell short of its January average by 1.8 inches, and Thurmond and Russell each missed their January averages by 1.5 inches. In spite of the rain shortfall, the reservoir levels rose, remaining slightly below seasonal guide curve. Winter guide curve or “full pool” gradually increases from Jan. 1 to April 1 when the guide curve defines summer full pool.
Hartwell and Thurmond lakes rose during the month because the rainfall-runoff ratio is higher in the winter than in the summer, according to Stan Simpson, a Savannah District water manager. With cooler temperatures and dormant plant life, a 1-inch rain event in the winter puts more water into the reservoirs than a 1-inch rain event in the summer, he said.
Hartwell sub-basin recorded 65 percent of its normal rainfall totaling 3.4 inches. The January average is 5.2 inches.
Thurmond sub-basin recorded 68.9 percent of its normal rainfall totaling 3 inches, and Russell sub-basin recorded 66.3 percent of its normal rainfall totaling 2.9 inches.
On Jan. 4, Hartwell and Russell sub-basins recorded their largest rain events receiving 1.3 and 0.7 inches, respectively. Thurmond sub-basin recorded its most significant rain event later in the month on Jan. 23, receiving 0.7 inches.
January marks the third consecutive month Hartwell sub-basin has fallen below its monthly average and the first time Thurmond sub-basin fell short of its average since November 2014. Additionally, Russell sub-basin received its lowest observed rainfall total since June 2014, when the sub-basin totaled 2.8 inches for that month.
~Chelsea Smith, Public Affairs Specialist