B. Everett Jordan Dam Sedimentation Rates and Reservoir Capacity ANNA J. PETRYNIAK AND APPLE B. LOVELESS JUNE 2013
OVERVIEW Reservoirs play a major role in North Carolina s water and energy supply. They are the storage sites of community drinking water, sources of hydroelectric power supply, and serve as flood control structures and sediment storage depositories. Residential and commercial development, as well as agricultural and industrial growth, increases erosion and sedimentation into reservoirs by clearing forested landscapes and increasing surface- runoff. Increased sedimentation can result in decreased reservoir capacity and threaten long- term water supply. The results below are based on a graduate student research project initiated by the Nicholas Institute for Environmental Policy Solutions to understand the extent of sedimentation and loss of capacity in North Carolina reservoirs. This paper provides a detailed report on major findings for B. Everett Jordan Dam within the context of all North Carolina reservoirs. While the majority of attention surrounds the ongoing assessment of water quality and nutrient management within Jordan Lake reservoir, our research on sedimentation rates can help uncover whether remaining sedimentation deposits pose an issue of capacity that should also be considered more actively as part of a broader water protection context. SEDIMENTATION AND RESERVOIR CAPACITY Sedimentation as a possible water resource issue can be seen either as a problem of quality or that of quantity. The scope of our study focuses primarily on sedimentation quantity. We look at numerous reservoirs in North Carolina to see if relatively large annual sedimentation yields pose its own set of resource problems, namely decreasing total water storage capacity at normal pool elevations within reservoirs. Quantifying sedimentation rates can also provide an assessment of how land use and cover have affected erosion rates and sediment production. Additionally, increasing yields should trigger environmental concern if sedimentation quality is known to be the cause or act as a sink for water quality constituents. CURRENT TRENDS IN NORTH CAROLINA The scope of the study spans 47 reservoirs, which includes: A comprehensive review of federal, state, and local government surveys; management plans; private studies; academic reports; stakeholder interviews concerning current data availability, sedimentation rates, and costs associated with sediment removal, monitoring and sedimentation prevention practices. In North Carolina, numerous entities spanning governmental agencies, private businesses, academic, and community groups are responsible for actively monitoring or holding historical data on sedimentation rates in NC. We found that entities initiated studies due to relicensing of hydroelectric projects, routine government surveys, and stakeholder and academic interest. Overall, however, data was not readily available for all reservoirs. In the appendix, Table 3 shows a breakdown of reservoirs that were studied and monitored by river basin. Thirty- eight
reservoirs, or approximately 81%, had data available. Amongst reservoirs with available data, only eight are monitored, which represents 21% of the total. 1 Unmonitored 30 reservoirs 79% The best- studied river basins consist of reservoirs managed by private companies. Possible explanations may include greater financial resources, government regulation, and increased importance on public reputation. Government agencies have also conducted thorough analysis of reservoir capacity, but are inconsistent in administering resurveys and are limited by funding. We observe that reservoirs managed by municipalities have the fewest resources to conduct studies and frequently rely on academia for detailed reports. This may be attributed to a lack of resources and pressing water quality concerns. The histogram on the following page displays the range of sedimentation rates in North Carolina, measured in acre- feet per year per square mile drainage area, ranging from a minimum of 0.003 for Falls Lake (in the Yadkin Pee Dee River Basin) to a maximum of 0.52 for W. Kerr Scott. The median statewide rate is 0.23, while the median range in the histogram is 0.25 0.275. Reservoirs in the Catawba Wateree River Basin were all in the median range or higher. With the exception of W. Kerr Scott, all reservoirs in the Yadkin Pee- Dee River Basin were in the median range or lower. All reservoirs in the Savannah River Basin fall below the median range. Results were variable in the Cape Fear River Basin. As for the Neuse River Basin, only three have available data and of those three, both Lake Michie and Little River were above median rates. Data for Falls Lake was collected by the U.S. Geological Survey (1976) and the U.S. Army Corps of Engineers (1972 and 1997). However, results showed capacity in the lake increasing with a sedimentation rate equal to - 0.95 acre- feet per sq. mi. drainage area per year. This is an unlikely result and stands out as an extreme outlier. 1 We define monitoring to include reservoirs where a sedimentation analysis has been conducted for
* Falls (Yadkin Pee Dee); Tiller; Blewett ** Badin (Narrows); Tuckertown *** Keowee; J. Strom Thurman ** ** Richard B. Russell; Stony Creek ***** Bridgewater; Fishing Creek; Great Falls & Dearborn, Rocky Creek and Cedar Creek; High Rock; Lake Michie; Little River *** *** Rhodiss; Oxford (lake Hickory); Lookout; C. Ford (Lake Norman); Wylie In most cases, only a single study has been completed for a reservoir, so that one number represents the sedimentation rate over time. In selected cases, multiple studies show a changing rate. In reality, a variable rate is more likely, which emphasizes the difficulty in understanding statewide trends and interpreting the effects of sedimentation on reservoirs. Where variable rates were available, some instances show sedimentation rates decreasing. This could be due to changing landscapes, better land management practices, corporate reputation, and increased effort at sedimentation mitigation and prevention measures. SEDIMENTATION CHANGES IN JORDAN LAKE RESERVOIR Haw River is impounded by the B. Everett Jordan Dam 4.2 miles above Chatham County, NC. Jordan Lake expands up into the New Hope River, which joins Haw River 0.3 miles above the B. Everett Jordan Dam, and goes through Wake, Durham, and Orange counties with the upper boundaries set between Durham and Chapel Hill, NC. (U.S. Army Corps of Engineers Wilmington District, 1997). The project is a multipurpose reservoir built for recreation, water supply, flood control, and releases to maintain downstream quality. It is divided into three separate pools for
flood control, conservation storage, and sediment storage, with allocations to water supply and low- flow augmentation constituting the conservation storage pool. Although initial sedimentation storage was based on an annual sedimentation rate of 0.5 acre- foot per square mile of drainage area, actual sediment storage in the reservoir was 74,700 acre- feet, which allows for a 0.44 acre- foot per square mile of drainage area annual sedimentation rate during the 100- year life of the dam (U.S. Army Corps of Engineers Wilmington District, 1997). The original 0.5 acre- foot per square mile of drainage area was calculated from the August 1953 U.S. Army Corps of Engineers (USACE) bulletin titled Summary of Reservoir Sedimentation Surveys Made in the United States through 1950. Sedimentation estimates were based on reservoir sediment survey data relative to the Cape Fear River Basin, providing a mean rate of 0.364 acre- foot per square mile of drainage area and a standard error of.054 (Kirkpatrick, 2012). Sedimentation surveys and data collected over the years have varied in range. According to the 1997 Sediment Resurvey report commissioned by USACE, the U.S. Geological Survey (USGS) made several pre- impoundment surveys of suspended sediment samples upstream of the dam from 1970 to 1979. Based on the assumption that 90 percent of the sediment would remain in the lake, a USGS report estimated a rate of 0.08 acre- foot per square mile of drainage area that would remain annually (U.S. Army Corps of Engineers Wilmington District, 1997). There have been three other sedimentation surveys completed since then by USACE and private contractors. The first survey took place from 1978 to 1979 before impoundment, a resurvey was conducted from 1988 to 1990, and a third resurvey was conducted in 1997. Table 1: Comparison of sedimentation rates and deposited amounts From 1979 1990 From 1990 1997 From 1979 1997 (11 years) (7.4 years) (18.4 years) Sediment Deposited 6,410 acre- feet 310 acre- feet 6,720 acre- feet Rate of 583 acre- feet per year 42 acre- feet per year Sedimentation or 0.34 acre- feet per or 0.01 acre- feet per year per square mile year per square mile of drainage area of drainage area Source: U.S. Army Corps of Engineers Wilmington District, 1997 365 acre- feet per year or 0.22 acre- feet per year per square mile of drainage area. The available data reveals that the amount of sediment deposited was much greater from 1978/9 to 1990 than from 1990 to 1997. The 1990 resurvey reveals a total volume increase of 6,410 acre- feet, while the 1997 resurvey indicates that only an additional 310 acre- feet of sediment was deposited since 1990. While the study acknowledges the possibility of inaccuracies, overall results point towards a decrease in sedimentation rates. Table 2: Reservoir Capacity Change in Sediment Storage Pool (150 202 feet MSL) Year Acre- feet 1979 original section capacity 74,700 1990 section capacity 68,348 1997 section capacity 67,767 Source: U.S. Army Corps of Engineers Wilmington District, 1997
It is important to note, however, that although the period between 1990 and 1997 saw decreasing sediment rates, parts of the Haw River and New Hope River channels several river miles above the dam accumulated sediment at levels similar to that seen from the 1979-1990 time period (U.S. Army Corps of Engineers Wilmington District, 1997). Our research covered 13 reservoirs within the Cape Fear basin, and the only one that was actively monitored was Jordan Lake reservoir. Although a 2012 resurvey was recommended, 1997 remains the most recent resurvey of B. Everett Jordan Dam. In comparison to the 28 other North Carolina reservoirs with available data, our research shows that sedimentation rates for Jordan Lake falls below the median. Based on comparable data, sedimentation does not seem to pose a large issue to the operation nor the reservoir capacity of B. Everett Jordan Dam. JORDAN LAKE LOOKING TO THE FUTURE As part of the 2008 Jordan Lake Drought Contingency Plan, the Corps is allowed to temporarily allocate surplus storage from the sediment storage pool to the conservation storage pool for water supply purposes during level 3 and 4 emergency drought situations (U.S. Army Corps of Engineers Wilmington District, 2008). In fact, drought conditions in 2007 necessitated the need for a temporary lease agreement with state of NC for such use (Young, 2010). The contract would allow for 60,000 acre- feet out of the 74,700 acre- feet of available storage in the sediment pool to be deemed as surplus (U.S. Army Corps of Engineers Wilmington District, 2008). Based on the section capacity listed in the 1997 resurvey, the Jordan Lake Drought Contingency Plan would leave 7,767 acre- feet available for sediment storage. Assuming that rates continue to be low, this may not pose a problem in the long- term. However, if rates return to that similar to 1978/9-1990 levels, then the reallocation option for droughts would not be available. While observed trends show that sedimentation has decreased since the early 20 th century, major cities in North Carolina are expected to grow, potentially reversing this trend. The North Carolina Office of State Budget and Management projects that the state population will grow by 11.5% from 2010 2020, and an additional 10.2% from 2020 2030 (2013). Over the next two decades, counties expected to have the fastest pace of growth include Durham, Orange, Wake, and Chatham in the Cape Fear and Neuse River Basins, as well as Cabarrus and Mecklenburg in the Catawba and Yadkin River Basins (North Carolina Office of State Budget and Management, 2013). Increased sprawl can produce higher sedimentation rates through construction and urban landscapes that augment sediment runoff. In combination with climate change predictions, reservoir capacity may decline rapidly. In fact, communities across North Carolina have experienced two severe droughts within the past decade, highlighting the confluence of these issues. Further research should also be conducted to compare sedimentation rates in other Piedmont states to better understand how rates compare nationally, and the specific forces that influence sedimentation rates in North Carolina. Increasing our understanding of these issues is critical, as the alternatives are costly.
SUMMARY OF MAIN POINTS Lack of current data for most reservoirs. Many are not being actively monitored which causes a lack of comparable data if and when a study has been completed. Out of 13 reservoirs in the Cape Fear basin, Jordan Lake was the only one with available data that was being actively monitored. The most recent completed resurvey for Jordan Lake is from 1997. The three sedimentation surveys of Jordan Lake reservoir show a decrease in sedimentation rates. From 1978/9 to 1990, volume increased by 6,410 acre- feet. From 1990 to 1997, sediment deposits increased in volume by 310 acre- feet. Jordan Lake reservoir sedimentation rates fall below the median compared to 28 other reservoirs. Although rates declined from 1990-1997, parts of the Haw and New Hope river channels above the dam do show sediment accumulation similar to 1979-1990 levels. The drought in 2007 spurred the need for reallocation from the sediment storage pool to the conservation storage pool. The proposed contract set a surplus of 60,000 acre- feet to be transferred from the 74,700 acre- feet of available storage. Based on 1997 estimates, the Jordan Lake Drought Contingency Plan would leave 7,767 acre- feet available for sediment storage, which may be an issue in the long- term if rates increase. Based on available data, sedimentation does not currently pose a threat to reservoir capacity. REFERENCES Kirkpatrick, Justin. (2012, October 9). Jordan Dam and Reservoir Sedimentation Resurvey, 1997. North Carolina Office of State Budget and Management. County/State Population Projections. Retrieved from: http://www.osbm.state.nc.us/ncosbm/facts_and_figures/socioeconomic_d ata/population_estimates/county_projections.shtm U.S. Army Corps of Engineers. (1953, August). Sedimentation Bulletin Number 5, Summary of Reservoir Sedimentation Surveys Made in the United States through 1950. Retrieved from: http://ida.water.usgs.gov/ressed/background/sedimentation- Bulletin- 5-1953.pdf. U.S. Army Corps of Engineers Wilmington District. (1997, August). Report of Sedimentation Resurvey, B. Everett Jordan Dam and Lake, Cape Fear River Basin, North Carolina. Retrieved from: http://epec.saw.usace.army.mil/1997_jordan_sediment_resurvey.pdf. U.S. Army Corps of Engineers Wilmington District. (2008, May). Environmental Assessment, B. Everett Jordan Dam and Lake, North Carolina, Drought Contingency Plan (Revised 2008). Retrieved from: http://www.docstoc.com/docs/49881075/b- Everett- Jordan- Dam- and- Lake- North- Carolina- Drought. Young, Tony. U.S. Army Corps of Engineers Wilmington District. (2010, May 05). Reservoir Management During Recent Droughts. [PowerPoint Document]. Retrieved from: http://www.nclakemanagement.org/conferences/presentations/se19may2010/young_05may1 0_SELakesMgmt_COE.pdf.
APPENDIX
Table 3: Available Data in Selected River Basins River Basin Reservoirs in Study 1 Reservoirs w/ Available Data 2 Reservoirs Monitored 3 Entities with Studies on Sedimentation CAPE FEAR 13 7 1 U.S. Army Corps; USDA; N.C. Urban Water Consortium; City of Greensboro; UNC w/ funding from OWASA NEUSE RIVER 5 3 1 U.S. Army Corps; City of Durham;City of Raleigh YADKIN PEE DEE 11 11 0 U.S. Dept. of Agriculture; United States Geological Survey; Alcoa; Army Corps; Duke University CATAWBA WATEREE 12* 12 6 Duke Energy; Catawba Wateree Management Group SAVANNAH 5 5 0 Duke Energy ROANOKE 1 0 1 U.S. Army Corps *Catawba Wateree River Basin consists of 11 reservoirs, but we are including Brown's Cove as a separate entity although it is part of Lake Wylie. This is due to focused research done on sedimentation in Brown's Cove and that dredging estimates of the area provide a current, actual dollar per a- f sq. mile. 1 Reservoirs in Study: Scope of reservoirs studied is not a comprehensive review of all river basins in North Carolina. Reservoirs within each river basin were selected by data availability and significance. 2 Reservoirs w/ Available Data: Studies have been completed where data regarding capacity loss and sedimentation were not made publicly available. Alternatively, sedimentation was not a concern of entity performing study. 3 Reservoirs Monitored: In this category, we include reservoirs where sedimentation is being monitored for more than one consecutive year or where a future resurvey is expected (dependent on funding).
Table 4: Selected capacity loss and sedimentation rates; highlights largest and smallest volume change in river basins studied. River Basin Years of Study Loss of Capacity CAPE FEAR Sedimentation Rate (acre-feet per sq. mile drainage area per year) University Lake 1932-1990 Total Loss: 20% 0.26 Jordan Lake 2 1979-1990 6410 acre-feet 0.34 NEUSE RIVER 1990-1997 310 acre-feet 0.02 Total Loss: 6720 acre-feet Average Rate: 0.22 Lake Michie/ Little River 1926-1992 Loss: 2,541 acre-feet 0.23 Falls Lake 1976 0.07 YADKIN PEE DEE 1982-1997 (-) 728 acre-feet (-) 2.89% (-) 0.95 High Rock Lake Annually: 0.36% 0.23 Badin (Narrows) Annually: 0.05% 0.03 CATAWBA WATEREE Rhodiss 1925-2006 Total Loss: 37.2% 0.31 Bridgewater (Lake James) SAVANNAH 1923-2006 Total Loss: 3.9% 0.23 Keowee 1971-2010 Total Loss: 6.553% 0.13 Richard B. Russell 1983-2010 Total Loss: 0.049% 0.18 ROANOKE Kerr Lake n/a n/a
Table 5: Sedimentation Data Sources Reservoir CAPE FEAR RIVER BASIN Brandt Burlington Sources United States Department of Agriculture, Reservoir Sedimentation Data Summary: Greensboro (Lake Brandt), October 1950, Available at: http://ida.water.usgs.gov/ressed/datasheets/6-3.pdf City of Greensboro Water Resources, personal communication, 2012. North Carolina Department of Environment and Natural Resources, Division of Water Quality, Environmental Sciences Section Intensive Survey Unit, Lake & Reservoir Assessments Cape Fear River Basin, June 04, 2009, Available at: http://portal.ncdenr.org/c/document_library/get_file?uuid=c71d5052-bd9d-4f99-9bf9-bcf66b562623&groupid=38364 North Carolina Department of Environment and Natural Resources, Public Water Supply Section, Capturing Sediment: Burlington, North Carolina, Available at: http://www.ncwater.org/pws/swap/pages/moreburlingtonsed.htm United States Department of Agriculture, Reservoir Sedimentation Data Summary: Burlington Municipal Reservoir, September 27, 1950, Available at: http://ida.water.usgs.gov/ressed/datasheets/6-9.pdf Cammack See Burlington Cane Creek Sedimentation information unavailable City Lake See Stony/Stoney Graham-Mebane Sedimentation information unavailable Higgins City of Greensboro Water Resources, personal communication, 2012. Jeanette Stow, Craig A and Wintergreen, James W., and Cason, Rebecca D. (November 2002). "Sedimentation and Water Quality in Lake Jeanette, Greensboro, NC" The research on which this report is based was funded by the City of Greensboro, NC, through the N.C. Urban Water Consortium. Project No. 50241 UNC-WRRI-SRS-22 Jordan US Army Corps of Engineers, Wilmington District "Report of Sedimentation Resurvey" B. Everett Jordan Dam and Lake, Cape Fear River Basin, North Carolina August 1997 Makintosh Sedimentation information unavailable Randleman Sedimentation information unavailable Reidsville Sedimentation information unavailable Stony (Stoney) City of Burlington, personal communication, December 5, 2012 Townsend City of Greensboro Water Resources, personal communication, 2012. Troublesome Creek University See Lake Reidsville Bises, James A. and Paull, Charles K. Sedimentation in University Lake, Orange County, North Carolina, University of North Carolina Geology Department, March 1994, A report prepared with the sponsorship and funding of the Orange Water and Sewer Authority, Orange County, North Carolina. CATAWBA WATEREE RIVER BASIN Bridgewater Catawba-Wateree Hydroelectric Project Sedimentation Monitoring Report Year 1 C. Ford (Lake Norman) Fishing Creek Baseline Data. Prepared for: Duke Energy Carolinas, LLC. Charlotte, NC. Prepared by: HDR Engineering, Inc. of the Carolinas. August 2011 Available at: http://catawbawatereewmg.com/2011/catawba-
Great Falls and Dearborn (GF-DEAR) Lookout Mountain Island Oxford (Lake Hickory) Rhodhiss Rocky Creek and Cedar Creek (RC- CC) Wateree Wylie Wylie: Brown s Cove SAVANNAH RIVER BASIN Hartwell Jocassee J. Strom Thurmond (JST) Keowee Richard B. Russell (RBR) NEUSE RIVER BASIN Benson Falls Little River Michie Wheeler ROANOKE RIVER BASIN Kerr Lake YADKIN- PEE DEE RIVER BASIN Badin (Narrows) Blewett Falls High Rock Rockingham Rocky River S. Yadkin Gage Wateree_Sediment_Report_Year_1_Final_2011.pdf Catawba Wateree Water Management Group, Sediment Monitoring Project (2013) Available at: http://www.catawbawatereewmg.org/projects.html CHEOPSTM hydro electric system simulation model Operations/Verification Report Appendix B: "Estimating Sediment Deposition and Volume Reduction in the Catawba-Wateree Resrvoirs (12 November 2004) http://www.dukeenergy.com/pdfs/cwcvreport_08_01_06a_.pdf DIEMER, J. (05/01/2011). "Sedimentation in a Piedmont Reservoir: Evidence from Brown's Cove, Lake Wylie, North Carolina". Environmental & engineering geoscience (1078-7275), 17 (2), p. 123. Mecklenburg County Water Quality Program, personal communication, November 2012. Duke Energy Carolinas, 2012, Keowee-Toxaway Hydroelectric Project (FERC No. 2503) Study Progress Report. Electronic Filing. June 15, 2012. FromDuke Energy Keowee-Toxaway Online Library. Available at: http://www.dukeenergy.com/pdfs/kt_progress_report_2012_06.pdf Sedimentation information unavailable US Army Corps of Engineers, Wilmington District "Report of Sedimentation Resurvey" Falls Lake Project, Neuse River Basin, North Carolina, July 1997. Weaver, J.C., 1994, Sediment characteristics and sedimentation rates in Lake Michie, Durham County, North Carolina, 1990-92: U.S. Geological Survey Water- Resources Investigations Report 94-4123, p. 34 Hazen and Sawyer, 2010, Technical Memorandum: City of Durham Dam Regulatory Compliance Study, Task 5: Reservoir Yield Evaluations. Prepared by Hazen and Sawyer for City of Durham. Aug 9 2010. Sedimentation information unavailable United States Department of Army Corps of Engineers, Reservoir Sedimentation Data Summary: John H. Kerr, March 1961, Available at: http://ida.water.usgs.gov/ressed/datasheets/6-11.pdf Yadkin-Pee Dee River Basin Plan, Chapter 3: Causes of Impairment and Sources of Water Pollution, Available at: http://www.docstoc.com/docs/107023876/yadkin-pee-dee-river-basin-plan- Chapter-3 Normandeau Associates, Inc. and PB Power, 2004, Sediment Fate and Transport Draft Report: Alcoa Power Generating Inc. Yadkin Division, Yadkin
Tillery Tuckertown Yadkin College Gage Project Relicensing (FERC No. 2197). Prepared by Normandeau Associates, Inc. and PB Power. December 2004. Available at: http://www.savehighrocklake.org/proj2197/iag/wq/finaldraftsedimentreport12 0904.pdf W. Kerr Scott U.S. Army Corps of Engineers, personal communication, 2012.