March deficits contribute to persistent drought

Rainfall last month continued the trend over the last 15 months that’s caused the drought conditions we currently experience. This is especially disappointing since March is typically the wettest month of the year.

By the numbers: Thurmond’s rainfall deficit was most pronounced, at 62 percent of normal for the month. Richard B. Russell observed 65 percent of normal and Hartwell observed 70 percent of normal.

Runoff indicates the basin’s poor conditions. The Broad River, our best indicator of natural runoff, is a major unregulated tributary in the basin. Its current 28-day average flow is at a record low this time of year – at or below one percent.

Let the reader understand: This means March stream flows have never been as low as they are now since we began keeping records.

The colored layers in the hydrograph below show percentile averages, with green being the normal range. The black line represents observed stream flow. When that line departs from the colored layers into the white, stream flows enter record territory for that time of year.

Hydrograph-edited

The hydrograph shows stream flows for the Broad River from January 2016 through April 2017 (in black). Historical data by percentile is represented by various colors.

Note how twice within 14 months stream flows have been on opposite extremes, as shown with the red circles. This demonstrates how in recent years weather patterns have grown increasingly unpredictable, with wet periods growing more extreme and dry periods enduring longer.

As of this writing intense rainfall is occurring in all three sub-basins giving a welcome head start to April’s rainfall. This is not a cause (yet) for optimism.

It will take more than a single intense rain event to recover from current conditions. We will need at least two solid rain events a month for several months to recharge the soils and better position the reservoirs for the coming recreation season.

Still, we have a good start so far for April, now logging more than 50 percent of normal rainfall in the first week.

Thanks for reading.

~Russell Wicke, Corporate Communications

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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