What does 6” mean for our lakes?
We recently submitted comments to the Federal Energy Regulatory Commission (FERC) on Duke Energy’s request to raise the Lake Norman, Lake Wylie and Lake James target elevations by six inches from May 1 to October 1. Do we oppose or support this? It’s complicated. Very complicated. We submitted our questions and concerns on this issue, which we have worked on for years.
Given our limited water supply and booming demands, water quantity is a critical issue for the Catawba River, perhaps more than any other river basin east of the Mississippi River. Linked to here is the full letter outlining our questions and concerns. Below are short and medium summaries.
Duke and drinking water utilities have been developing a long-term computer model (CHEOPS) and Water Supply Master Plan (WSMP) for water availability in this basin. The additional water would add some volume in case we got into dire drought conditions like in 2007-2008. However, holding additional water could also have implications for flooding impacts when we receive heavy rain. Mountain Island Lake and Lake Wateree in particular are prone to extreme flooding and lie downstream of where additional water would be held. Flooding is only worsening from the same amount of rain because of increasing impervious surface area from lake-area development. We have a lot of questions and concerns with the computer model and WSMP (documented in our letter).
As part of Duke’s privilege to manage and profit off of the Catawba River (the water of which belongs to the public), it must keep multiple interests in mind (e.g., recreation). The character and usability of the lakes revolve around their levels (target elevations), which are regulated by Duke Energy’s hydroelectric project license issued by FERC.
The vast majority of the Catawba River is dammed up to where lakes back up to the dam of the reservoir upstream. Heavy rains mean water must be passed through the system. Some dams (e.g., Norman, Wylie) have flood gates so that those reservoirs never go above full pond (100’). Other dams (e.g., Mountain Island) have spillways and are limited in the infrastructure they can adjust to allow more water to pass through; water can quickly rise. If the reservoirs are already holding more water, flooding would presumably be worse.
The group of Duke Energy and 18 public water supply utilities on the Catawba (19 total entities with major intakes on the Catawba) comprise the Catawba Wateree Water Management Group (CWWMG), which has produced the WSMP based on Duke’s CHEOPS hydrologic computer model runs. Our concerns lie especially in the ability of CHEOPS to accurately model the basin. We have received graphs showing CHEOPS runs indicating Lake Norman (the only reservoir for which these graphs were produced) would be held at full pond 25-30% of the time whether or not water conservation measures of the WSMP were implemented. Historically, Norman has been at full pond less than 1% of the time. Mountain Island (the next reservoir below Norman) would be extremely vulnerable to flooding were Norman held at full pond 25-30% of the time. Norman is 12 times as large as Mountain Island, so dropping Norman one inch equates to Mountain Island rising 12 inches. Recent flooding incidents have damaged or destroyed docks, watercraft and even homes. Lake Wateree’s flooding is less sudden, but it endures for a long period of time.
Because of CHEOPS’ issues, we have concerns with the accuracy of Duke’s model runs of increased flood impacts from its reservoir increases. These model runs submitted in its application to FERC included few details on the conditions of the runs.
We have larger questions about how raising three reservoirs 6” actually helps with long-term water quality. Indeed, it could help during drought – but truly, how much? The CWWMG purports that this is a key strategy of the WSMP.
We have a lot of other concerns with the WSMP, including possible disproportionate impact to Lake James given that there are no intakes on the lake except for the hydroelectric power intake at the dam – 50 feet down and far deeper than any other reservoir. So, could Lake James be disproportionately drained in the WSMP? Thus far, for what we have seen in the WSMP and its CHEOPS modeling, there is no assurance. We asked for graphs of reservoir elevation over time (duration) for Lake James especially but also all other Catawba lakes. We have never received these graphs.
Is the WSMP balanced? Have water conservation strategies been researched with due diligence? The WSMP does not look at the largest source of water loss (net use, aka consumption) – thermoelectric power generation, which needs water for cooling and evaporates off 75 million gallons each day. Instead, the WSMP looks to curtail public water supply use, drop intake elevations and raise water levels. But a balanced WSMP needs a balance of strategies that both increase accessible volume and decrease the approach to having water levels drop below intake structures.
The current application should not be approved without additional information and conditions:
- Demonstrated improvements to the accuracy CHEOPS, especially in its portrayal of lake levels in compliance with reservoir elevations prescribed by Duke’s FERC license (i.e., not showing a reservoir being held at full pond 25-30% of the time)
- New elevation duration charts need to be generated once CHEOPS can demonstrate an ability to accurately model water throughout the basin
- Clear documentation for how FERC and the public can recreate CHEOPS’ results when CHEOPS is applied for various calculations
- New analysis and more details on the analysis for additional days of spillover that could be caused by an additional six inches in Lakes James, Norman and Wylie from May 1 to October 1
- Clarification on how additional spillover days are being calculated/modeled
- Acceptance of CHEOPS modeling for additional spillover days only if CHEOPS is proven accurate and consistent
- In the CHEOPS model, thorough consideration of changes to hydrologic runoff response from increasing impervious surface area (likely to exacerbate flooding and spillover)