March rainfall below average; but summer predictions improve

March is normally the wettest month of the year in the Savannah River Basin, but this year we experienced below-average rainfall in both the Hartwell and Thurmond sub-basins for the month.

RainfallBarGraphMarch

The Hartwell sub-basin recorded 78 percent of normal rainfall in March. It received 4.66 inches, falling short of the March average of 5.97 inches.

The Thurmond sub-basin came much closer to achieving average rainfall, reaching 93.8 percent of normal. It received 4.47 inches compared to the March average of 4.77.

On Saturday March 30, Thurmond reached its highest level in over a year and a half when it climbed to 324.09 ft/msl. The last time Thurmond was higher was on Aug. 28, 2011 with an elevation of 324.34 ft/msl. At that time, the basin was about one month into the current drought.

February rainfall also helped with this recovery, as Thurmond received 6.85 inches of rainfall in February—greatly exceeding the February average of 4.35 inches. In fact, Thurmond finished February at 157.5 percent of normal rainfall. Hartwell also received above average rain in February with a recorded 5.39 inches, slightly exceeding the monthly average of 5.07 inches.

Not only has the winter rainfall raised the pools, it has also improved our projections for the summer forecast.

In our post on Feb. 20 “Our Forecast on Summer Reservoir Levels” we expected to start the summer at levels similar to 2012, more than 8 feet below full summer pool. But now our 10-week projection shows that Hartwell will remain relatively steady between 655 and 656 ft/msl through June 1, and that Thurmond will gradually climb to around 326 ft/msl.

Essentially, our new prediction is that we expect to enter Memorial Day with both reservoirs about 4 feet below full pool—nearly double the amount of recovery than what we originally predicted. This is good news for the basin; but we proceed with prudence. We aren’t out of this drought just yet. The only solution to end the drought is long-term, average or above-average rainfall throughout the basin—especially during the summer months.

What can we expect in April? The basin’s average rainfall for April is 4.58 inches at Hartwell and 3.52 at Thurmond. We’ve already got a good start so far with rainfall earlier this week. A normal or above-average April rainfall will improve basin conditions even more. As the weather warms, we’ll get less return in lake levels from rain because of transpiration and evaporation.

For now, we continue to hold releases at the minimum rates during the drought. The basin operating status remains in drought level 2; thus minimum outflows are 4,000 cfs (if Broad River flows exceed 10 percent of the historical flow rate) and 3,800 cfs (if Broad River flows are less than or equal to 10 percent of the historical flow rate).

~Tracy Robillard, Corporate Communications Office

This map shows the sub-basins within the Savannah River Basin.

This map shows the sub-basins within the Savannah River Basin.

About US Army Corps of Engineers Savannah District

The U.S. Army Corps of Engineers Savannah District oversees a multi-million dollar military construction program at 11 Army and Air Force installations in Georgia and North Carolina. We also manage water resources across the Coastal Georgia region, including maintenance dredging of the Savannah and Brunswick harbors; operation of three hydroelectric dams and reservoirs along the upper Savannah River; and administration of an extensive stream and wetland permitting and mitigation program within the state of Georgia. Follow us on Twitter @SavannahCorps and on Facebook.com/SavannahCorps
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