By COL Thomas Tickner
Savannah District Commander
This past weekend Thurmond Reservoir levels dipped below 326 feet above mean sea level, which is the marker for our first drought trigger. This level indicates the Savannah River Basin (SRB) is in mild drought.
Operationally, this means we will restrict release rates at Thurmond Dam to 4,200 cubic feet per second (cfs) until Hartwell and Thurmond reservoirs rise 2 feet above the trigger points for Drought Level 1.
Our drought plan stipulates that if either reservoir descends 2 feet below the first drought trigger, or if inflow from the Broad River, an unregulated tributary feeding Thurmond, falls below the 10th percentile of the 28-day average, we will further reduce our outflows to 4,000 cfs. The 28 day average streamflow at the Broad River gage is currently averaging about 18% of normal. Based on current conditions and extended forecasts, I believe it is unlikely we will experience Drought Level 2 in the near future. There are a few reasons for this.
Forecast: All the recent drought forecast models indicate neutral conditions for our area for the next three months. See the U.S Seasonal Drought Outlook, which extends to Dec. 31, below.
Current precipitation: Although we observed below average rainfall in June, July and August, it looks like we will finish September with above average precipitation.
ENSO Forecast: Using ocean temperature indicators, NOAA produces the ENSO forecast to identify the kind of weather conditions expected in the northern hemisphere from year to year. Temperatures can indicate either El Niño conditions (wet), La Niña conditions (dry) or neutral (average conditions). In general the ENSO forecast is very useful. For example, every drought in the SRB has occurred during NOAA’s declared La Niña conditions. According to NOAA’s Climate Prediction Center, “Most models favor El Niño (greater than or equal to +0.5°C) to develop during October-December 2014 and persist through Northern Hemisphere winter 2014-15.” This suggests we will have normal to wet conditions through December.
The above three indicators do not amount to certainties that we will be relieved of drought conditions over the winter. But these models and predictions come from experts in climatology – and they are the best sources of information we have.
I understand our stakeholders benefit from full reservoirs. Therefore when drought conditions do emerge, I also understand stakeholders experience a degree of hardship in proportion to the intensity of the drought.
I share your concerns during periods of rain deficits and I am committed to an efficient operation that meets the needs of all who depend on the SRB for water – upstream and downstream.
Because I share your concerns, I monitor the basin’s conditions regularly and keep a close eye on the forecast, especially during this period of mild drought.
Until water levels recover I urge caution when boating, swimming or fishing during the next weeks. When reservoir levels decline, underwater obstructions are closer to the surface. This becomes a particularly dangerous circumstance for boaters and skiers. Swimmers should not venture outside designated swimming areas. All visitors should wear a life jacket when swimming, boating or fishing.
We’ve made it easier for stakeholders to get information on basin conditions through our new mobile app, launched back in August. I encourage you to download this free app from your mobile device’s application store, by searching “USACE Savannah”. With this app you have access to near-real-time data on rainfall, lake levels, outflows, projections and more from almost anywhere.
Thank you for your patience and understanding. And as always, we welcome your feedback in the comment section below.