Chattahoochee River, Georgia
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An Economic Analysis of Selected Strategies for Dissolved-Qxygen Management: Chattahoochee River, Georgia GEOLOGICAL SURVEY PROFESSIONAL PAPER 1140 An Economic Analysis of Selected Strategies for Dissolved-Oxygen Management: Chattahoochee River, Georgia By JOHN E. SCHEFTER and ROBERT M. HIRSCH GEOLOGICAL SURVEY PROFESSIONAL PAPER 1140 A method for evaluating the cost effectiveness of alternative strategies for dissolved- oxygen management is demonstrated UNITED STATES GOVERNMENT PRINTING OFFICE, WASH INGTO N : 1980 UNITED STATES DEPARTMENT OF THE INTERIOR CECIL D. ANDRUS, Secretary GEOLOGICAL SURVEY H. William Menard, Director Library of Congress Catalog-card No. 80-600113 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 CONTENTS Page Page Abstract __________________________________________ 1 Estimation of costs: benefits foregone and waste-treatment Introduction _______________________________________ 1 costs __________________________________________ 13 Nature of the problem ____________________________ 1 Estimates of benefits, given 1954-56 drought conditions _ 14 Buford Dam _______________________. 1 Recreation ____________________________________ 14 Relationship of flow and dissolved oxygen ______. 3 Hydroelectric power and peak generating capacity ___ 14 Managing the dissolved-oxygen concentration _____. 3 Estimation of average annual benefits _________________ 16 The range of alternatives _______________. 4 Estimation of added waste-treatment costs _____________ 17 The alternatives considered _____________________ 4 The reregulation project _______________________________ 18 Study overview _______________________, 5 Least-cost method of producing a given minimum dissolved- The dissolved-oxygen model ___________________________ 5 oxygen concentration _____________________________ 21 Results from the dissolved-oxygen model _________ 6 Sensitivity of the least-cost solution to the cost of depend able peak-generating capacity ______________________ The hydrologic simulation model ________________________ 7 21 Operation of the Buford Dam hydroelectric generating Institutional constraints and associated costs ______________ 23 facility: assumptions and definitions ___________ 9 Concluding remarks ___________________________________ 24 Description of the hydrologic simulation model ______ IQ References cited ______________________________________ 25 Results from the hydrologic simulation model _______ H Appendix A-Analysis of the reregulation project ___________ 25 ILLUSTRATIONS Page FIGURE 1. Graph showing dissolved-oxygen concentrations at the Fairburn, Ga., station monitor and mean daily discharge at the Atlanta, Ga., station during July 1977 ________________________________________—————— 2 2. Schematic map of the study reach of the Chattahoochee River, Ga ___________________________—————— 3 3, 4. Graphs showing: 3. Minimum dissolved-oxygen concentration as a function of minimum flow at the Atlanta, Ga., gage, given that 48 percent of the waste flow receives nitrification, for 1990 conditions ____________________————__ 6 4. Relationships of parameters of aQA + b=D to percentage of total waste flow receiving nitrification ________—__ 7 5-7. Iso-dissolved-oxygen curves showing combinations of percentage of total waste flow receiving nitrification and minimum dis charge at Atlanta, Ga., that are predicted to result in minimum dissolved-oxygen concentrations of 3, 4, and 5 mg/L: 5. For 1980 conditions __________________________________————————————————————— 8 6. For 1990 conditions ________________________________________________________ 8 7. For 2000 conditions __________________________________________————————————— 9 8. Diagram showing simulated releases at Buford Dam, Ga., during weeks 33 and 40 of 1954, given a minimum flow at Atlanta, Ga., of 1,290 and 1,600 ft3/S, For 1990 conditions ____________________________________ 13 9-12. Graphs showing: 9. Pool elevations of Lake Sidney Lanier, Ga., over the period of simulation, given that the minimum flow at Atlanta, Ga., is set at 1,290 and 1,600 ft3/s, for 1990 conditions ______________________________——___ 14 10. Benefits from recreation on Lake Sidney Lanier, Ga., given various pool elevations ———————————————————— 15 11. The relationship between average annual benefits foregone and minimum flow at Atlanta, Ga., for 1980, 1990, and 2000 _________________________________________________————————————— 18 12. The estimated annual cost of adding a nitrification process to secondary waste-treatment plants, as a function of the percentage of the total waste flow receiving nitrification ___________________————————————— 19 in IV CONTENTS Page Fici'KKs 13,14. Diagrams illustrating: 13. The method of determining the least-cost combination of the percentage of waste flow receiving nitrification and the minimum flow at Atlanta, Ga., required to produce a minimum dissolved-oxygen concentration of 4 mg/L, in 1990 ______________________________________________________ 19 14. The solution for least-cost combinations of percentage of wastes receiving nitrification and minimum flow at Atlanta, Ga., necessary to produce a minimum dissolved-oxygen concentration of 5 mg/L, for 1980, 1990, and 2000 _________________________________________________ 21 15. Graph showing the costs (benefits foregone plus added waste-treatment cost) of attaining various minimum dissolved- oxygen concentrations under different policies for 1990 _______________________________—___ 24 16. Diagram illustrating the relationship between estimated annual dependable-peaking-capacity benefits and minimum flow at Atlanta, Ga., with and without reregulation, for 1980, 1990, and 2000 __________________________ 26 TABLES Fagv TAHLK 1. The expected average daily flow from waste-treatment plants discharging to the Chattahoochee River between Atlanta, Ga., and Whitesburg, Ga., in 1980, 1990, and 2000 ________________________________________ 6 2-4. Withdrawals from: 2. Lake Sidney Lanier, Ga ______________________________________________________ H 3. The Chattahoochee River, Ga., from Buford Dam to Morgan Falls Dam ___________________________ 11 4. The Chattahoochee River, Ga., from Morgan Falls Dam to the Atlanta gage ________________________ 12 5-7. Hydrologic-simulation-model results: 5. Of water discharge and electric-power production of Buford Dam, Ga., for 1990 conditions ________________ 12 6. For years 1980, 1990, and 2000 _________________________________________________ 12 7. And estimated benefits for 1990, given certain minimum flows at Atlanta, Ga., under 1954-56 drought conditions __ ig 8. The average daily flow from waste-treatment plants discharging to the Chattahoochee River between Atlanta, Ga., and Whitesburg, Ga., and the annualized cost of adding a nitrification process to the plants ____________________ 18 9. Combinations of percentage of wastes receiving nitrification and minimum flow at Atlanta, Ga., that will provide minimum dissolved-oxygen concentrations of 3, 4, and 5 mg/L at least cost, for 1980, 1990, and 2000 __________________ 20 10. Costs of dependable peak generating capacity above which the indicated minimum dissolved-oxygen concentration can be achieved at least cost by operating Buford Dam, Ga., so as not to forego benefits from dependable peak generating capacity_ 22 11, 12. Economic-efficiency loss if least-cost combination of the percentage of wastes receiving nitrification and the minimum flow at Atlanta, Ga., is selected under the assumption that the cost of peak generating capacity: 11. Is $23.34/kW/yr but actual cost is $49.35/kW/yr _________________________________________ 23 12. Is $49.35/kW/yr but actual cost is $23.34/kW/yr ________________________________________ 23 13. Percentage of wastes that must receive nitrification to provide minimum dissolved-oxygen concentration of 3, 4, and 5 mg/L at least cost, given that the minimum flow at Atlanta, Ga., is constrained to 860 ft3/s, for 1980,1990, and 2000 ___ 24 AN ECONOMIC ANALYSIS OF SELECTED STRATEGIES FOR DISSOLVED- OXYGEN MANAGEMENT: CHATTAHOOCHEE RIVER, GEORGIA By JOHN E. SCHEFTER and ROBERT M. HIRSCH ABSTRACT (milligrams per liter), 10 percent of the time (Stamer and other, 1978). The periods of low DO concentrations A method for evaluating the cost-effectiveness of alternative strategies for dissolved-oxygen (DO) management is demonstrated, us occurred primarily in the summer and autumn. During ing the Chattahoochee River, Ga., as an example. The conceptual October the DO concentration was less than 5.0 mg/L 31 framework for the analysis is suggested by the economic theory of pro percent of the time-more often than in any other duction. The minimum flow of the river and the percentage of the total month. waste inflow receiving nitrification are considered to be two variable The occurrences of low DO concentrations correspond inputs to be used in the production of given minimum concentration of DO in the river. Each of the inputs has a cost: the loss of dependable closely with the occurrences of low discharge of the peak hydroelectric generating capacity at Buford Dam associated with river. This relationship can be seen in figure 1, which flow augmentation and the cost associated with nitrification of wastes. shows (top) the average daily DO concentration at Fair- The least-cost combination of minimum flow and waste treatment burn and (bottom) the average daily discharge at Atlan necessary to achieve a prescribed minimum DO concentration is iden ta, which is about 1.5 days