More rainfall, but where is it all going?

Things are starting to look up for the Savannah River Basin as each of the sub-basins received above average rainfall for the third straight month.

Russell led the charge in June, netting 7.2 inches compared to its 3.8-inch average. (This was Russell’s fourth best in the past 69 years; the most for June came in 1989 at 8.21 inches.)

Thurmond and Hartwell received 6.6 and 5.7 inches on 3.8- and 4.8-inch averages, respectively.

These numbers are especially encouraging as the precipitation has come at a time of year not normally associated with heavy rainfall.

So with all this rain – for instance, the Hartwell sub-basin has collected 6.4 inches above its average in the last three months – why haven’t the reservoirs fully recovered?

The answer is complicated.

For starters, the basin is still recovering from one of the worst droughts in its history. In 2016, the sub-basins had the worst or second worst single year for rainfall on record.

In addition, the effects of the drought were muted due to the torrents of rain we received at the end of 2015. Essentially, that rainfall carried us through the first six months of the drought.

So even though the basin started receiving below-average to severely below-average rain from January to July 2016, the water table and reservoir levels were still being buoyed by the rain we received from October through December 2015.

Finally, timing is everything.

Much in the way that the winter 2015 rainfall delayed the drought’s effects, the drought is prolonging the time it takes for the water table and reservoirs to recover.

In addition, the excess rainfall we’ve been receiving is now being “taxed” by transpiration and evaporation, so a smaller percentage is actually making it to the reservoirs. This effect happens every summer, but was exacerbated by the drought.

Thurmond observed and average rainfall from July 2015 to present.

So while Thurmond received 14.3 inches above its average in the winter 2015 compared to an excess of 6.8 inches from April to June 2017, those 14.3 inches were amplified further because a greater percentage of that precipitation actually reached the reservoir.

Similarly, had those additional 6.8 inches come earlier in the year, say from January to March, it would have been a different story.

~ Jeremy S. Buddemeier, Corporate Communications Office

About U.S. Army Corps of Engineers Savannah District

The U.S. Army Corps of Engineers Savannah District oversees a multimillion 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
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