Why Irma rainfall had marginal effects on levels: inflows remain below average

Many basin stakeholders have expressed interest in why reservoir levels didn’t respond better to the Hurricane Irma rainfall received on Sept. 11 and 12.

The previous post was intended to assure the public there was sufficient storage capacity in our reservoirs to absorb the forecasted rainfall. Based on that forecast which predicted 7 inches of rain, we estimated Hartwell would rise 3.5 feet and Thurmond up to 6 feet. That message was important for the general audience because some were suggesting the reservoirs should be lowered in anticipation of the rain event. Lowering reservoir levels in anticipation of forecasted weather is against Corps policy and deviates from the water manual.

As Hurricane Irma continued to shift westward, actual observed rainfall was much less than NOAA’s forecast of 7 inches. Instead Thurmond received 2.5 inches of rain and Hartwell less than 2.1 inches, definitely not enough to cause flood concerns, so attention shifted to anticipated benefits of the rainfall.

Despite the 2-plus inches of rainfall, Hartwell and Thurmond barely responded. Let me first reassure readers what did not cause unresponsive levels.

We did not increase discharge to make room for rainfall. Nor did we increase discharge after Irma rainfall. In fact, due to persistent drought we have maintained releases at approximately 4,000 cubic feet per second (cfs) or less from Thurmond for more than a year now. This is the minimum release rate allowable for Drought Level 2, and it follows the directives of the drought plan. We didn’t deviate from the water manual throughout Hurricane Irma.

So why did the reservoirs respond so poorly to Irma rainfall?

The answer is limited runoff. The dry ground soaked up most of the rain before it could make its way into the reservoirs. Exceptionally dry conditions have driven inflows down to a minimum level requiring additional rainfall before runoff occurs.  Hartwell has a 12.4 inch rain deficit over the last 12 months.

Rainfall has improved over the last several months, but it is normal for pools to decline this time of year with average rainfall. We need sustained above average rainfall for conditions to improve. Every drought we’ve experienced has been overcome by a return to above average rainfall, and we anticipate a similar recovery with this drought.

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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  • Ferris

    Thanks for the illustration Russell!
    The large acreage dedicated to farming contributes to lower runoff rates for low rainfall amounts in line with the topic discussion, particularly during the growing season. Naturally, farmers plow fields to direct runoff to water crops that readily absorb initial rainfall as the soil becomes a bit wetter. The 2.5″ and less from Irma spread over 2 days added to soil saturation somewhat as shown in the illustration, with much absorbed by crops and other “taxes” discussed previously.

  • LittleBigPaw

    We’ve heard all the reasons “WHY” the lake can’t reach full pool, so maybe Russell can’t explain what it would take to achieve full pool. Chief meteorologist, John Cessarich, in today’s paper says the upstate rainfall is over 7″ above normal, evidently he has misspoken. I understand from passed reports the corp propery is still at drought levels so other than 3 or 4 feet of rain what would it take?

    • Ferris

      LittleBigPaw 09/23/2017
      “We’ve heard all the reasons “WHY” the lake can’t reach full pool, so maybe Russell can’t explain what it would take to achieve full pool. Chief meteorologist, John Cessarich, in today’s paper says the upstate rainfall is over 7″ above normal, evidently he has misspoken. I understand from passed reports the corp propery is still at drought levels so other than 3 or 4 feet of rain what would it take?”

      No one from USACE has said, “the lake can’t reach full pool”.
      Cessarich primarily covers the Greenville area, which is outside the SRB. Only a portion of Upstate SC includes the Hartwell Basin.

      • LittleBigPaw

        What would it take to fill the lake?

        • Ferris

          LittleBigPaw=> Ferris 09/23/2017
          “What would it take to fill the lake?”
          An immediate return to normal inflows that lasts through mid-Feb would bring lakes to Full Pool. Dec-Apr inflows are especially important for groundwater recharge and refilling lakes.
          Unfortunately, the long term NOAA Outlooks show below average rainfall and above average temperatures through at least Jan. The USACE hydrologists Projection shows only 60% of normal inflows through Nov.

          • Thanks for answering Ferris – you are correct. Although, I will add it may not be as dire as the forecast makes it sound. NOAA’s long term forecasts are notorious for failing to accurately predict conditions months out.

            What will it take for a return to normal inflows? Two to three intense rainfall events (roughly 2 or more inches of rain in a 12 hour period) a month throughout the fall and into winter. If we get rainfall like that, inflows will return to normal. And it wouldn’t have to be extraordinarily above average rainfall, just a little above monthly averages. That kind of rain would achieve enough purchase to put the reservoirs back to full. I hope this helps. ~Russell Wicke

          • emac1234

            Actually all it will take to fill the lake is to let less water out than comes in. But the current system does not allow that to happen unless we get crazy amounts of rain at just the right time. Which rarely ever happens.

          • We share your concerns and understand the difficulty people deal with during drought conditions. Problems occur downstream as well as up stream. But understand that at the peak of the 2016 drought, we could have completely eliminated discharge from Thurmond and the reservoir would still have declined. Natural inflows were lower than evaporation, transpiration and groundwater loss at that time.

            It is also important to consider populations downstream depend on discharge for drinking water and other municipal needs and industry depends on the river for their products that contribute to the regional economy. Also, treated wastewater is discharged into the river requiring dilution in order to avoid harmful impacts to the environment. With all these considerations, the Savannah River below Thurmond has a legitimate need for minimum releases. I hope this helps. ~Russell

  • Johnny Landreth

    I think that something is wrong with the calculation of gallons released. I live just off the Seneca river and we received 6 inches of rain at my house and the water level has dropped below where it was before Irma. We’ve had this happen over and over again on Hartwell lake with no explanation that makes sense. I think that we may have a problem at the dam or either we have human error that is not being detected by the managers. Maybe an audit of discharges should be made by an independent engineering group.

    • Ferris

      The NOAA map includes the two days of Irma rainfall and confirms the event average 2.1″ for Hartwell Basin. Localized intensity generally renders a single location measurement meaningless when considering the basin average.

      Downstream gauges confirm the accuracy of average releases.

      No explanation will make sense without accepting that evaporation, transpiration, and groundwater recharge dramatically reduce the inflows required to raise lake levels.

  • Georgette

    Maybe it is time to re-evaluate the Corps Policy and the water plan. Look at Russell! The policy and plan for it is much different than those for Thurmond and Hartwell. Russell is hardly ever below 2 feet. It just doesn’t make sense to keep our lake at such a low level. RE-EVALUATION TIME!!!

    • Hello Georgette – thanks for your comment. The Russell Reservoir and dam are different because the project was designed as a pump back facility. The reservoir is smaller and has much less conservation storage. It can only function as it does because Hartwell and Thurmond enable it with their current operation. All three were designed together as parts to a system. They each have their role, and cannot continue deliver the product they were designed for if operated independently. I hope this helps. ~Russell

      • Georgette

        Thanks for your reply. I do have another question…After the rain from Irma, the water came up real good in our Ski and the next day that amount was gone plus a lift more. If the output stays the same, why did we loose the water that came up plus more? Thanks for trying to help me understand this.

        • I’m happy to help where I can Georgette. I can’t know for sure the cause of what you observed without more information on your specific location. Reasons can differ depending on whether you’re on Hartwell or Thurmond as well. But I can off some possible explanations.

          It could have been a case of what is called “tilt”. This is caused by sustained high winds from one direction that reverse as the storm passed. Water piles to one side of the reservoir, and then as wind shifts it piles to the other, distorting the even balance of water.

          Intense localized rainfall may have been a contributor. This is where one particular area may have received disproportionate amounts of rainfall causing water in that area to swell, but then as time passes it equalizes with the rest of the reservoir. This is called pool shift.

          If you are on Hartwell, a contributing factor could have been an increase in release into Russell on Sept. 14 and 15. We would have done this to balance out the pool levels through the system. Hartwell and Thurmond share water resources so that if one benefits with a surplus of rain, both do. And if one suffers deficit, impacts are mitigated by the other reservoir absorbing some of the deficit.

          If you are at Thurmond, a cause might have been water being pumped upstream into Russell Reservoir. If this were the case the water would not have been lost because it is always released back into Thurmond from Russell.

          The phenomenon may have had an unknown cause as well. When dealing with immense surface areas of water, and more than 10,000 square miles in the basin, we sometimes see effects from causes in nature that go unobserved.

          I’m open to further discussion if you have other questions. ~Russell

  • emac1234

    After over 15 years of dealing with this, I discovered if you want water in the summer, you need to go to another lake or build a pool. Don’t waste your time with the CORPS. Its like gambling. They give you just enough hope to keep you coming back. But you can’t beat the house. The cORPS gives you an excuse and Ferris cheerleads for them as the water goes down stream. Disgusting.

    • Don’t be too quick with your judgement about Ferris. Like you, he has his own interests as a downstream stakeholder, just different interests from upstream. And to be sure, there are records here on this blog where he and the Corps have had sharp disagreements about the operation. ~Russell Wicke

    • Ferris

      Ernest Mccallum, what you cannot beat is science, and I am definitely a cheerleader for science. Tell me how my science is wrong, because science will win. What is disgusting is to try to change science with politics and opinions.

    • emac1234

      As i see it.
      The CORPS issues dock and other permits for landowners/businesses/public to use the lake. They dont mind raising the fees and collecting the money, but they seem to have little interest in preserving the lake. After repeated droughts, coves are silting in, trees are growing on the shores, and docks/infrastructure/property values are being damaged. I think the CORPS should bear some responsibility to their “customers”.

      As I recall, in a past drought, the CORPS lowered outflow to around 3600. I dont recall any huge uproar from downstream folks. We would be in a lot better position now, if we had lowered outflow a long time ago. The CORPS has admitted that weather patterns have become more extreme, so why not adjust to the changing climate?

      I am not asking for a full pool year round, all I am asking for is to be treated fairly as an equal partner. We pay all the fees, excessive property taxes, etc and we get no representation. All I ever hear is lip service. We have to draw an inside straight to win, everyone else gets a couple of wildcards to play.

      Yes, I realize the CORPS has nothing to do with property tax and probably has no obligation for shallow coves and trees growing on the shoreline, but it doesnt mean I have to approve of it.

      As for the science….A wrong diagnosis will always lead to a wrong treatment plan. In order for me to believe your science, I would have to agree with your current diagnosis (the CORPS plan). The CORPS plan only works when we have “normal” rainfall. Well, if you know any stats, you understand averages are just averages. They tell you nothing about a specific year. One year we get a ten inches of rain, the next year we get 20 inches. The average is 15. So what? Those years are totally different and would require different management by anyone depending on rainfall, like farmers. Hence, the farmers almanac and long term weather forecasting.

      • Ferris

        The science follows what natural resource agencies say are minimum downstream flows for water quantity and quality for the river and freshwater estuary based on available data. There was a big outcry from these agencies at 3,600 cfs releases, and I have posted quotes from these agencies on this blog. They agreed to 3,600 cfs only during the less critical months of Nov – Jan and for DL4 as a “fair” sharing of drought pain for upstream and downstream stakeholders. If or when these agencies agree that lower releases are acceptable, then so be it; but lower releases may require an EIS. The plan has to work downstream also. My take is that protecting the freshwater estuary prevents lower releases, but that mitigation would quickly hit other limits in the river and harbor.

        I consider USACE initiating and sponsoring continuing iterations of drought plan revisions much more than lip service. USACE continues pushing for lower drought releases, but available data for the natural resource agencies science limits how low rates can go. However, lake levels are higher than they would have been without USACE pushing for lower releases. Evaporation, transpiration, and groundwater recharge science reduce lake inflows. Natural resource agency science determines drought releases. At this time, the difference results in low lake levels, and my posts attempt to explain why from a somewhat different perspective than USACE.

  • Cliff Smithson

    Does lunar influence create measurable tides in Clark’s Hill Lake?

    • Thanks for the question Cliff. I’ve read that the Great Lakes have “mini” tides due to their size. But if there is any lunar effect on Hartwell or Thurmond, it is immeasurable. ~Russell Wicke

  • Mark Welborn

    The “management plan” is guaranteed to leave Lakes Hartwell and Thurmond well below guide rule or reasonable levels a high percentage of the time. It promises lower stream stake holders an unnaturally high flow at the economic and quality of life expense of upstream residents and property owners. We have a very unfair “management plan”.

    • Ferris

      Your posts over the years have shown an “unnatural” affinity for the word “unnatural”. You conveniently ignore that the “unnatural” dams withheld river water to fill the “unnatural” lakes in the beginning and provide only a ration downstream except when levels exceed full pool. HRT “unnaturally” withholds a permanent 53% of capacity in the inactive pools. Your unwillingness to share the “unnaturally” withheld water by calling it “very unfair” without a specific recommendation that can be discussed says it all. To quote your projection from the Mar 4 2015 topic, “I guess I could say that you have an insatiably selfish nature but I think that’s apparent on its own”.

      Mark, accept responsibility for building where Hartwell at 656.7′ becomes a “very large mud hole” (Jul 15 2016 post to Jul 13 2016 topic); USACE operational changes have contributed to relatively higher pool elevations since you first lived in the area. Unlike most lakefront homeowners, you are “old enough to remember what the Keowee and Seneca River basins were like prior to the building of the impoundments” (Mar 18 2015 topic) and should have known better than to build on such a shallow cove considering historical Clark Hill operations.

  • Clay

    So why is it that other non-Corps lakes such as Burton, Keowee, and Oconee are not in the same predicament? Your water (mis) management plan needs to be changed!

    • Ferris

      HRT effectively blocks the path of a major river and must maintain minimum downstream flows for 240 miles of river and the harbor estuary, a requirement not shared with Burton, Keowee, or Oconee. HRT covers a total 153,000 acres compared to 2,775 acres for Burton, 18,500 for Keowee, and 19,000 for Oconee. Congressional project approvals included power generation pools 25′ deep for Thurmond, 45′ deep for Hartwell, and 5′ deep for Russell. These depths allow maintaining minimum downstream flows even during extreme droughts.

      • Mike Killian

        Ferris, your comments, while informative, always seems to echo/support the Corp’s positions. I think you either work for the Corp…or have…or want to. Are you and Russell the same person?

        • Ferris

          USACE and I base our comments on scientific data from many of the same sources, so we will agree most of the time. Neither of us supports low lake levels, but current data indicates the alternative is severe to permanent downstream damage. I just happen to be the primary individual downstream stakeholder with the time and interest to comment on this blog. You may read my comments in the AVM EA Appendices to see that I am a real person. When you read my comments in the final Comprehensive Study EA Appendices, you will see that I strongly disagree with the USACE recommendation based on my understanding of the data they presented, or failed to present.

          • Mike Killian

            Sorry, but I remain unconvinced. Retired – or not – you clearly spend many, many hours on this blog parroting the Corps. That’s certainly your choice. It does call into question your motives. Listen, I hold no ill-will against you or the Corps. There does need to be an intellectually honest assessment of water management policies and practices without all of the spin because it sure doesn’t work for many of us today.

          • Ferris

            Your statement reflects only unsubstantiated opinion. You did not research my AVM comments, and you have not thought through your comments and insults.

            – USACE would probably severely reprimand or even fire an employee for deceptively posting with an alias.
            – Your only evidence for the plan not working is that the lakes are not full, but congress has not authorized full lakes as part of the project purposes. I could say you are just parroting what other lake folk say on this blog, calling into question your motives. Simply wanting full lakes is just an opinion, not science.
            – You have obviously not studied documents in public domain including all of the drought studies, comments to the drought studies, and research forming the basis of the drought studies. NOAA and USGS provide other public domain resources.
            – Your accusations of USACE intellectual dishonesty and political spin are completely unwarranted and based on your lack of objectivity. Of course, we usually agree because the public domain scientific research agrees. Although vocal on this blog, lake folk are not the only stakeholders.
            – I have spent many hours over the years researching studies from various organizations, but am typically on this blog only when I get an email notice of a new topic or post.

            Catch up later, leaving for a brief Florida trip.

          • Mike Killian

            Unlike yourself, I do not have hours to spend on this blog. I don’t pretend to work for the Corps as you do. And I sure am certainly not inclined to “read your AVM EA”… how arrogant you would believe anyone would be interested! Enjoy your trip to FL, perhaps it will provide you with a broader perspective.

          • Ferris

            Mike Killian, you continue advertising your lack of objectivity and comprehension, which your name calling accentuates. Rather than arrogantly calling me “arrogant”, you could broaden your perspective, if you have the capacity. Since you obviously keep your head in the sand and think you know everything about me, you should know that Florida recently suffered a major hurricane. My trip was work rather than pleasure; a last minute schedule change made it a 6 day rather than a 3 day trip.

            You asked, “Are you and Russell the same person?”
            I replied, “You may read my comments in the AVM EA Appendices to see that I am a real person.” I do not care whether you or anyone else reads the comments, but the correspondence conclusively shows I am not Russell Wicke. Only someone unfamiliar with writing style analysis would have made such an uninformed assumption in the first place.

            You again stated, “I remain unconvinced” and further accused me of “parroting the Corps”. Perhaps you should lookup “parroting”. I created the many charts included with my posts from public domain data; show me where USACE has posted these. On the Sep 10 topic, I am the one who kept adding inflows to the lake level conversation, a theme Russell followed on the Sep 22 topic.

            I wrote, “I am retired and have no interest in another job. I have never worked for USACE in any capacity.”
            You wrote, “I don’t pretend to work for the Corps as you do.” Your statement is an intentional lie, plain and simple, or you are very stupid. Yeah, I do impugn your motives.

          • Thank you Ferris and Mike for contributing to the discussion here. I propose moving on from this conversation before it escalates to violation of our posting guidelines (posted under the “About” tab). I don’t think it has reached that point, but here is a good place to leave it. Thanks! ~Russell Wicke

          • Mike Killian

            Russell, I agree. This back-and-forth serves no purpose. As stated above, I have no ill-will toward Mr Ferris or the Corps. I only want there to be an intellectually honest discussion on the policies and practices. I do not believe anything I have posted constitutes defamation or is hateful. The most egregious comment could have been referring to Mr Ferris as being “arrogant” by expecting people to spend valuable time researching his writings and posts.

            However, he has now accused me of of being a liar and stupid. I am busy and will gracefully leave this blog on my own for a time. If decorum is important here – and, IMO it certainly should be – it does seem Mr Ferris should get a time-out so he’s not on here insulting other contributors. Thanks MK

          • Concerned

            I think Ferris has run the show on this blog long enough. Arrogant is a kind description of his inappropriate comments to anyone who disagrees with him.

    • Good question Clay. You are asking about reservoirs from Georgia Power and Duke energy, and their reservoirs were designed with different requirements in mind. They are specialized reservoirs intended to function with one or two particular purposes, serving a commercial need that is best suited with a narrow range of water levels. Corps reservoirs in the Savannah River Basin (HRT), not only have different purposes, but have numerous purposes (seven) most of which place a demand on water within the system, and none of which require stable levels. In fact, engineers designed Thurmond and Hartwell to fluctuate based on differing needs at different times. Also, Thurmond is the last reservoir in linear succession on the Savannah River, and therefore specified minimum discharge is required to meet municipal, industrial and environmental needs downstream. None of the reservoirs you mentioned are in this situation. I hope this helps. ~Russell

      • Elisabeth White Putnam

        My ten year old son could balance the basin better than what y’all are doing!! Why do you drop the lakes so drastically starting in August? We are not in the drought that you claim we are & if our non Corp. run lakes can balance their water levels then why can’t we??

  • Jerry Clontz

    all the talk about science and engineering determining the lake levels by virtue of releases required is a bunch of bull. we all know that 3600cfs meets all the engineering and scientific needs. that being true the corps needs to drop releases from Thurmond to 3600cfs anytime the lakes can not be held at full pool. let’s face it. the Corps doesn’t give a damn about the unbelievable waste in recreational value (eg. lake Murray) they are causing. they use the excuse that SEPA ties their hands and that is just not true.

    • Ferris

      Jerry Clerry, USACE does not blame SEPA for drought releases, you do. Bull, Bull, you are Full Too! Your plan puts downstream in permanent adverse conditions except when it floods.

  • Clay

    So basically Lake Hartwell property owners are screwed.

    • LittleBigPaw

      That’s a given as long as they follow their dated plan. It proves that the architects of plan had little foresight when considering climate change.

      • LittleBigPaw, regarding your reference to the Corps’ “dated plan,” how old do you think the current drought plan is? ~Russell Wicke

  • Concerned laker

    Can you say. Class actiin lawsuit. Silted coves, damaged land prices. Damaged boats. Damaged docks. Really and higher taxes. What a deal. I signed up twice. Wow

  • WK Jr

    I’m curious: the data presented on the Corps site reflecting avg vs observed rainfall for the Hartwell basin indicates that since April there has been only two months where the observed rainfall failed to meet or exceed the avg rainfall– in July and Sept. The data indicates Oct is also below, but we are already at over 5 inches observed, whereas the avg is only 4 in, so Oct is high. I understand that Oct thru April was in deficit, but we are now at least at avg in total rainfall if not higher– have the outflows been kept at minimal, and if not, why not? Minimal release should be defined as the minimal required to fulfill all the “needs”, right?

    • Thanks for the comment WK and good question. You are correct that beginning in April, rainfall has improved, with some months above average and others below. And this is what normal/average rainfall looks like. But in order to understand why the reservoirs aren’t full, we have to include in our consideration the months from when the drought began, which goes back to January 2016. From that time until March 2017 there was a 28 inch rain deficit. A mere return to normal rainfall won’t result in a recovery to full reservoirs. Average rainfall from that point will only arrest the decline and hold levels relatively steady. In order to recover from rain deficits, we need rain surplus. Just as the rain deficits endured for months, we would also need a surplus to endure for months. The good news is, this will happen as it always has historically. And today’s rainfall is a great step in the right direction. (You’ll need to give our site time to update today’s 3 inches at Hartwell. It hasn’t cached in all the areas yet, and it is still falling. Also, reservoir levels need time to respond to rainfall).

      As to your question about outflows, Questions 15 and 23 on our FAQ page linked in the banner of this blog, should be useful.

      I hope this helps. ~Russell Wicke

      • WK Jr

        Thank you.