January’s Rainfall was better – but more is needed for recovery

Rainfall Chart

The first month of 2017 brought a welcome change in rainfall; all three sub-basins exceeded average precipitation for the first time in almost five months.

Hartwell received 104 percent of normal rainfall; Russell, 115 percent of normal; and Thurmond cashed in at a healthy 138 percent of normal – just over 6 inches of rain.

Even better, much of the rain we received came in the form of high intensity rainfall events. Hartwell and Russell each had one major rain event that brought about 2.5 inches over three days (from Jan. 21-23). Thurmond observed two major rainfall events making up most of its total rainfall. The first occurred Jan. 1-3 with about 2.5 inches and the second Jan. 21-23 with just under 2.5 inches.

Although this is better news, it’s not great news.

Runoff (and not rainfall) is the best indicator of recovery. The distinction between rainfall and runoff is very important. Rainfall deficits of the previous 12 months caused the ground to dry out significantly. Dry ground greatly reduces the runoff ratio to rainfall. This explains why Thurmond can receive 138 percent of normal rainfall, yet runoff for the same time period remains at 68 percent of normal. Dry soil is a relentless creditor. On “payday” it demands a full settlement on outstanding debt.

As mentioned in a previous post, to recover from this drought by the 2017 recreation season, rainfall must come in the form of high-intensity events. The reservoirs respond much better to an inch of rain when it falls all at once; thus increasing the runoff ratio. Contrarily, that same inch of rain received over many days will absorb into the dry soil. It will never become runoff in the current condition.

Furthermore, we said recovery would require at least two high intensity events across the upper basin each month through spring. January rainfall did not deliver (fully) on this. Hartwell and Russell had one major event. Thurmond had two.

Therefore rainfall trends in the next several months will prove crucial in determining reservoir levels by summer.

A look at the below 10-week projection for Hartwell offers a sober prediction where levels will peak if inflows don’t return to 100 percent or more of normal from now through spring.

Hartwell Projection

Thanks for reading. We welcome your feedback.

~Russell Wicke, Corporate Communications Chief

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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5 Responses to January’s Rainfall was better – but more is needed for recovery

  1. Johnny Landreth says:

    The rain will not bring the lake up unless we reduce the flow. Last year we finished 2 inches above normal rain and we gained no ground in our lake levels. Proper management is what we need to bring the lake levels up. The corps has known for the last ten years that we need to reduce the flow. We need to allow the lake to come up now. They are predicting long term drought again for the next 12 to fourteen months. Most of our rain will be at the beginning of the year. Please cut the flow. I would think that continuous low water levels would be an embarassment to me, if I was in charge of lake water levels. Evidently, the corps is going to force us to endure extremely low water levels again this year. The environment or weather has changed over the last twelve to fifteen years and the corps has not changed its management techniques. Most boat ramps remain closed. Property values have plummeted. The management doesn’t care. I believe that the corps has it in for us water lovers, boat enthusiasts, and fishermen and they don’t care about us United States citizens. Well, I guess its time to change and we may have to change management to get the job accomplished. Let’s all start writing our government about the problem and ask for new managers. We’ve tried to reason with the corps but they won’t listen.

  2. Johnny Landreth says:

    I would love to be able to bragg on the corps rather than criticize them. It is very hard to look at our lakes and be proud when our upper lakes are so full. The reason I guess is that duke energy engineers are better managers.

    • US Army Corps of Engineers says:

      Hello Johnny – Duke’s reservoirs (Jocasse and Keowee) are also down. They are in a storage balance agreement with the Corps based on conservation storage available. ~Russell Wicke

      • Johnny Landreth says:

        I went by them yesterday and they were full. Please cut the flow.

        • Ferris says:

          Duke Energy shows Keowee at 796.2′ on Feb 2 2018 (today), down from a maximum 800′. Comparing current elevations to those seen in the past would cause one to think the lake is “full” because of Duke Energy Agreement revisions.

          I have not found the following concisely defined, but think it correct.
          – The 2014 Duke Energy Agreement calculates remaining conservation storage above 790′ compared to 778′ in the 1968 plan. The change allows the Oconee Nuclear Station to operate during low drought levels.
          – The USACE Hartwell Presentation on Jun 26 2017 shows Keowee matches USACE projects conservation storage remaining from 80% down to 12%. USACE projects conservation storage remaining: 82% DL1, 73% DL2, 43% DL3. The USACE water management page shows 75% conservation storage remaining today, so Duke Energy projects should have the same amount.

          Duke Final EA and New Operating Agreement Oct 2014
          – Figure ES-1 shows the 2014 plan (A3) releasing a cumulative 100,000 AF less water to USACE projects than the 1968 plan (NAA) from Jul 1 2007 through Dec 10 2008, with releases averaging 95 cfs less. A3 averages 355 cfs releases for the period, down from 450 cfs for the NAA.
          – For the period, models indicate minimum Keowee elevations of 782′ for the NAA and 790′ for A3 (pages 3-31, 32).

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