STORAGE ANALYSIS FOR THE ACF, ACT AND SAVANNAH RIVER BASINS George McMahon' and Pat Stevens' AUTHOR: 1 Principle Environmental Engineer, Camp, Dresser & McKee, Inc., 2100 RiverEdge Parkway, Suite 500, Atlanta, Georgia 30328; 2 Chief, Environmental Planning Division, Atlanta Regional Commission, 3715 Northside Parkway, 200 Northcreek, Suite 300, Atlanta, Georgia 30327 REFERENCE: Proceedings of the 1995 Georgia Water Resources Conference, held April 11 and 12, 1995 at the University of Georgia, Kathryn J. Hatcher, Editor, Vinson Institute of Government, the University of Georgia, Athens, Georgia. Abstract. The HEC-5 model is used to: 1) evaluate in Lake Lanier from hydropower use to water supply use. operational approaches for reservoirs in the ACF, ACT, and The Corps also proposed a minor reallocation of Lake Savannah River systems; and 2) determine the impacts of Allatoona to meet a portion of the Region's future needs. future Atlanta area water withdrawals and increased In June of 1990, the State of Alabama, later joined by the minimum flows at Columbus, Georgia. A Dependable State of Florida, sued the Corps for inadequate consideration Capacity Operation approach is recommended. This of downstream impacts. In order to address concerns approach maximizes economic benefits of hydropower and precipitating the Alabama lawsuit , the Corps and the states allows other water demands to be met through and beyond of Alabama, Georgia, and Florida entered into a the year 2010. Memorandum of Agreement to perform a comprehensive study of all major water-management objectives in the ACF PURPOSE and ACF Basins. The study is designed to determine the capabilities of the basin's water resources. It will describe This study was performed by Camp, Dresser & McKee, Inc demands, water availability, evaluate alternatives and (CDM) and coordinated by the Atlanta Regional recommend a coordination mechanism for basinwide Commission(ARC) for DelCalb, Fulton and Gwinnett management and dispute resolution. Initial results are Counties, the Cobb-Marietta Water Authority, the City of scheduled for Fall, 1995. Atlanta, the Columbus Water Works, and the Georgia Power Water managers in the Atlanta Region wanted to conduct Company. The purposes of the study were: 1) To evaluate, a surface water model project to better understand the water compare and suggest specific approaches to operating resources system and the conjunctive uses of reservoir federal reservoirs in the Apalachicola-Chattahoochee-Flint storage. The Columbus Water Works joined the project to (ACF), the Alabama-Coosa-Tallapoosa (ACT), and explore the feasibility of maintaining higher flows at Savannah River Basins for a variety of conjunctive uses Columbus for water quality and navigation. including hydropower, municipal and industrial (M&I) water supply, minimum flows for river water supply, water quality and navigation, and reservoir recreation; and 2) To STUDY AREA determine the impacts of increased 2010 Atlanta area water withdrawals and increased minimum flows at Columbus for Three river/reservoir systems were included in this effort: water quality and navigation under drought conditions, in the Apalachicola-Chattahoochee-Flint River Basin (ACF) comparison to present (1990) water demands in the ACF which stretches from the north Georgia mountains to the and ACT Basins. Gulf of Mexico; the Alabama-Coosa-Talapoosa River Basin (ACT) which extends from the north Georgia mountains to Mobile Bay in Alabama; and the Savannah River Basin BACKGROUND from north Georgia and North Carolina to the Atlantic Ocean. The surface water model simulates operations for Lakes Lanier and Allatoona, which currently provide most multiple uses in the ACF and ACT Basins. The Savannah of the Metropolitan Atlanta Area's water supply, were River Basin Reservoirs were included only for the purpose of planned, designed, and constructed during the late 1940's simulating their contribution to the hydropower system. and early 1950's. These projects were built for flood control, Hydropower energy and capacity from 10 federal hydropower, and in the case of Lanier, for navigation and reservoirs in these basins are marketed as part of a federal water supply/quality flows for Atlanta. In recent decades hydropower system known as the Georgia-Alabama-South recreation has assumed much greater importance. Carolina system. The projects which make up this system In 1989, after 16 years, the U.S. Corps of Engineers are U.S. Army Corps of Engineers projects and include: recommended that the best alternative to provide water Hartwell, Russell, and Thurmond Dams on the Savannah supply for the Atlanta Region and Lake Lanier communities River, Buford, West Point, and Walter F. George on the was to "reallocate" or change a portion of the water storage Chattahoochee River, Allatoona Dam on the Etowah River, 294 Carters Dam on the Coosawattee River and Jones Bluff and 107% to 131% of the rated capacity of the projects for 4 Millers Ferry Dams on the Alabama River. hours per weekday on an average annual basis. A federal agency, the Southeastern Power Administration, markets the power from this system and therefore the 10 3. Corps Water Control Plans. This approach dam system is commonly referred to as the SEPA system. associates releases with pool levels and not actual demands. Although the Jim Woodruff project in the ACF Basin is In 1989 the Corps of Engineers developed a water control included in the model, the hydropower energy and capacity plan for the ACF Basin. In 1993 a Water Control Plan was results were not included in summaries because its power is developed for the ACT Basin. Theses plans define "action not marketed as part of the 10 dam system. Also included in zones" for each of the major storage projects in the basins. the study were 12 non-federal hydropower reservoirs owned These zones are used to determine minimum hydropower by the Georgia Power Company and the Alabama Power generation at each project, as well as the maximum possible Company (APCO) and two nonpower reservoirs. Non- assistance for navigation from conservation storage. The federal reservoirs on the Talapoosa and Flint were not Corps water management strategy is to balance operation included. among purposes and projects. Releases from projects will be balanced as near as possible so that the reservoir pools in the same basins will be in the same zones at the same time. The OPERATIONAL APPROACHES ANALYZED number of hours use associated with the Water Control Plans varies by zone. In the ACF, Zones 1 & 2 varies from 4 to 3 The study looked at three different operational approaches hours use and Zones 3 & 4 vary from 3 to 2 hours use. In for providing hydropower capacity and energy in the ACT, Zone 1 is 4 hours and Zone 2 is 2 hours use. conjunction with other nonpower demands. The three approaches analyzed include: 1. Dependable Capacity Operation. This approach is a METHODOLOGY conservation based approach. Its intent is to conserve storage and minimize releases in manner so that the The HEC - 5 Model. essential uses of all users can be met. Hydropower releases are conjunctive with most other uses and determined by the This study used the Corps of Engineers' computer program, firm energy available to support dependable capacity of the HEC-5 Simulation of Flood Control and Conservation system. This is the capacity that is dependable to displace Systems which is referred to as HEC-5. HEC-5 is used to thermal generating capacity. If hydro-capacity is not account for surface water at various locations in a river dependable and power users must purchase power from basin, over a given period of time. The program was existing thermal sources during drought, then the developed by the Corps of Engineers' Hydrologic hydropower allocation really wasn't essential and could be Engineering Center (HEC) to assist in allocating flood put to other water dependent uses. control and conservation storage in a reservoir system. It This approach operates the river/reservoir system to imitates (simulates) the operation of a system of reservoirs in produce the amount of peaking hydropower that is a river basin and is therefore called a simulation model. The dependable during the critical period of drought. A worst program can therefore be used to determine the impact of case planning level approach is used which assumes that alternative ways in which a system of reservoirs are only the generating capacity of the hydro system that can be operated. made simultaneously available to displace thermal capacity The main demands for water storage from a reservoir that in the load can be considered dependable. The average can be simulated by the HEC-5 program include: hours of use of the system is the number of hours per • Municipal and industrial water supply from reservoirs and weekday averaged over a year that the full system's capacity downstream; can actually be made available during the critical drought. • Hydroelectric power generated at the dam; Two and one half (2 1/2) average hours use was used as • Control of downstream flooding; the basis for the dependable capacity alternative approach. • Assurance of minimum flows to assimilate wastewater discharges 2. SEPA System Contract Minimum Energy. The • Adequate river levels to assure navigation approach maximizes energy generation rather than capacity. The HEC-5 model consists of two basic components: This approach operates the system for 4 hours average use reservoirs and control points. These components are per weekday on an average annual basis. This was chosen connected by river channels. Figure 1 includes the federal because It more closely -reflects SEPA's monthly contract and non-federal reservoirs and control points included in the minimum energy commitments which are based on the HEC -5 model for this study. combined output of all system projects operating from 295 MAJOR ASSUMPTIONS AND INPUTS CCIAWA, ACP I Ceder/ale Crionettfihdonl IUD Table 1: Municipal and Industrial Withdrawals and Carlerefilan ■ /D W/0 Wier Hartwell Ceingell/Pultgo Mon Returns ef Mom /brume Falb COM Relum---- 1990 2010 ACF Withd.