2013 SAVANNAH RIVER BASIN HYDROLOGY RECAP

By Jason Moak, Research Scientist

Last year was a wet year.  A really wet year!  Based on historical data from a weather station at Bush Field Airport, the average annual rainfall from 1981 – 2010 was 44 inches.  In 2013, that same station logged almost 56 inches of total rainfall.  That’s a whole foot of extra rain!  What’s even more impressive is that a large portion of that total was experienced in just two months – with close to 20 inches of rain in June and July. All this rain was a good thing.  Much of the Savannah River Basin (SRB) had been experiencing extreme drought since 2010.  The Palmer Hydrological Drought Index (PHDI) is used to characterize wet or drought conditions and reflect conditions in rivers, reservoirs, and groundwater.  The PHDI scale generally ranges from -4, representing extreme drought, to +4, representing extremely wet conditions.  The SRB began 2013 with a PHDI value of -3.2, indicating severe drought.  However, the above average rainfall moved the SRB index into the moderately moist range, where it presently remains. The effects of all of this extra rain could certainly be seen in the upstream lakes.  On June 8, 2013, Lake Thurmond reached full pool, 330 feet above mean sea level (ft msl) for the first time since February 2010.    Lake Hartwell reached full pool (660 ft msl) on May 24, 2013 for the first time since June of 2011. Perhaps the most dramatic of all the effects of this extra rainfall were seen in the Savannah River.  Based on the US Geological Survey gauge at New Savannah Bluff Lock and Dam, the daily average discharge in the Savannah River was 24,534 cubic feet per second (cfs), which was by far the highest daily average discharge since Thurmond Dam construction was finished in 1954.  In terms we can all understand, in July 2013, the amount of water in the Savannah River that flowed past the CSRA was enough to fill 24,088 Olympic swimming pools each day!