On Sept. 18 we commenced the Second Interim of the Savannah River Basin Comprehensive Study, bringing us six months into the process. In this post, I hope to provide a brief update on the progress as well as shed some light on the nature of the study itself.
To restate, the entire Comp Study is broken up into three interim phases. The phase in progress now is the second interim, scheduled to last 18 months. The purpose of this interim is to answer the following questions:
- How low can we reduce daily outflows at the Thurmond Dam during drought conditions?
- How many days can we sustain these minimum outflows before significant impacts would occur to the economy and environment?
Alternative Drought Operations Considered
To determine answers to the above questions, six alternative drought operation plans are being modeled as part of the study. In each alternative, we study the consequent values, risks and impacts in the basin to be expected during drought. We will consider and compare these alternative operating plans against what we call the “No Action Alternative,” which is our current drought contingency plan. The alternatives being modeled and compared to our current drought operations are:
- Extreme Drops: This alternative considers extreme reductions in outflows for each drought trigger. For example, the model considers a reduction of releases to 3,500 cubic feet per second (cfs) in Drought Level 1. In Drought Level 2: 2,500 cfs. In Drought Level 3: 1,500 cfs.
- Higher Drought Level Elevation: This alternative considers redefining the elevation at which Drought Level 3 occurs. Currently, Drought Level 3 is defined as 14 feet below summer full pool with a minimum outflow of 3,800 cfs (3,100 cfs in November-January). This alternative would define the third drought level at 8 feet below summer full pool, with a minimum outflow of 3,600 cfs.
- Release Based on Environmental Flow Restriction: This alternative incorporates a predictable pattern with a wide variance of outflow volume based on seasons, conditions, available rainfall and environmental requirements.
- 3,600 CFS Constant: This alternative reduces all outflows immediately to 3,600 cfs at the first drought trigger and maintains this outflow until the reservoirs rise two feet above the first drought trigger. During the months of November through January, the outflow would drop to 3,100 cfs.
- Combination or Any Other: This alternative allows us to incorporate favorable parts of the above alternatives and combine them into a single alternative. Or, we could consider a completely different set of flow restrictions not considered in the other alternatives.
- Rate of Rise on Recommended Plan: This is only a supplement to the selected alternative put in place. It will define operating protocol during drought conditions when the reservoir levels are rising. For example, it will consider options such as holding outflows at the amount prescribed from the lowest Drought Level reached until the pools are refilled.
Adaptive management opportunities are being considered in each of these alternatives.
Progress to Date
For each of these alternatives a model must be built. Raw inflow information must be collected and then filtered to exclude irrelevant data. Once we have a clean set of data to plug into each alternative, the models will produce results. These results will be compiled, evaluated and documented in a report.
Currently the Georgia Environmental Protection Division is compiling the raw inflow data. This information is being filtered and we expect an updated data set for the basin at the end of this month. From here, we will run one alternative at a time through the model and compile results. Based on where we are right now in the study, we have approximately 12 more months before receiving a final report with all the findings.
As always, we welcome your questions, comments and feedback in the comments section below. Thanks for reading!
~Russell Wicke, Corporate Communications Officer