HOOVER POWERPLANT MODIFICATION FEASIBILITY REPORT APPENDIX C HYDROLOGY MAY 1981 PREPARED BY BUREAU OF RECLAMATION LOWER COLORADO REGION APPENDIX C - HYDROLOGY TABLE OF CONTENTS Page I. INTRODUCTION .....C-1 A. Purpose .....C-1 B. Background .....C-1 C. Location .....C-1 D. Climate .....C-1 E. Alternatives Considered .....C-1 1. Surface .......... C-1 2. Underground Powerhouse .....C-1 3. Replacement of Units A8 and A9 .... C-2 4. Pumped-Back Storage .....C-2 II. WATER SUPPLY AND RESERVOIR OPERATION .....C-3 A. Present Condition .....C-3 1. Water Supply .....C-3 a. Runoff .....C-3 b. Demands .....C-3 2. Reservoir Operation .....C-5 a. Control of River Operations .....C-5 b. Forecasted Water Supply .....C-6 c. Scheduled Annual Water Requirements . C-7 d. Daily Water Requirements .....C-8 e. Daily Operations .....C-8 f. Water Scheduling - Power Generation Relationship .....C-9 g. Historic Operational Data .....C-10 h. Weekly Release Patterns .....C-12 B. Future Conditions .....C-13 1. Water Supply .....C-13 a. Runoff .....C-13 b. Demands .....C-17 2. Reservoir Operation .....C-17 3. Lake Mohave Operation Study .....C-27 a. Study Results .....C-29 b. Study Evaluation and Conclusions . C-30 C-i TABLE OF CONTENTS (continued) Page III. TAILWATER STUDIES .................................. C-32 A. Introduction .................................. C-32 B. Design Discharges C-32 C. Water Surface Profiles ........................ C-34 1. Cross Sections ............................ C-34 2. Steady Flow Tailwater Study ................. C-35 3. Calibration of Unsteady Flow Model ......... C-35 4. Calibration of 1979 Steady Flow Model ....... C-38 5. Projections for Additional 500-MW Powerhouse ................................ C-44 6. Projections for Other Alternatives ......... C-48 D. Cofferdam Studies .............................. C-53 1. Introduction .............................. C-53 2. Cofferdam Studies No. 1 and No. 2 ........ C-53 3. Cofferdam Study No. 3 ............ C-53 4. Cofferdam Study No. 4 ................... C-54 E. Hoover Powerplant Modification Degradation Study C-55 1. Introduction .............................. C-55 2. Present Channel Conditions ................. C-55 3. Degradation Analysis ...................... C-55 4. Conclusions .............................. C-58 F. Proposed Powerhouse Discharge Study ............. C-59 1. Introduction .............................. C-59 2. Analysis .................................. C-59 3. Conclusions .............................. C-60 G. Head Loss Study ................................ C-60 1. Introduction .............................. C-60 2. Analysis .................................. C-60 a. 500-MW Powerplant ................... C-60 b. A8 and A9 Alternative ................. C-64 3. Conclusion ................................ C-64 C-ii TABLE OF CONTENTS (continued) Page IV. WATER TEMPERATURE STUDIES .......................... C-65 A. Discharge Temperature Study ..................... C-65 1. Introduction .............................. C-65 2. -Analysis .................................. C-65 3. Conclusions .............................. C-73 B. River-Lake Interface Study ..................... C-74 1. Introduction .............................. C-74 2. Analysis C-74 3. Conclusions .............................. C-75 C. Ground-Water Conditions at Willow Beach National Fish Hatchery ........................ C-75 1. Introduction C-75 2. Available Data ............................ C-75 3. Conclusions .............................. C-76 BIBLIOGRAPHY ........................................... C-78 LIST OF TABLES No. Page 1 Colorado River Transit Times ........................ C-9 2 Physical Characteristics - Hoover Dam and Powerplant . C-11 3 Physical Characteristics - Davis Dam and Powerplant. C-11 4 Low Discharge Extremes at Hoover Dam ................. C-12 5 CRSP Hydrologic Sequences .......................... C-14 6 Estimated Future River Losses and Gains Lower Colorado River Hoover Dam to the Northerly Internationl Boundary (NIB) ........................................... C-18 7 Consumptive Use of Diversions from Mainstream, States of Arizona and Utah above HoovPr Dam and Hoover Dam to Parker Dam C-19 8 Consumptive Use of Diversions from Mainstream, State of Arizona, Parker Dam to Imperial Dam ............... C-20 C-iii TABLE OF CONTENTS (continued) LIST OF TABLES (continued) No. Page 9 Consumptive Use of Diversions from Mainstream, State of Arizona, Imperial Dam to NIB and below .....C-21 10 Consumptive Use of Diversions from Mainstream, State of California from Nevada-California Boundary to Parker Dam .....C-22 11 Consumptive Use of Diversions from Mainstream, State of California, Parker Dam to Imperial Dam .....C-23 12 Consumptive Use of Diversions from Mainstream, State of California, Imperial Dam to NIB .....C-24 13 Consumptive Use of Diversions from Mainstream, State of Nevada, above Hoover Dam to Nevada-California Boundary .....C-25 14 Peak Discharges .....C-34 15 Colorado River Cross Sections .....C-36 16 PSEUDO Calibration Results .....C-37 17 Calibration Coefficients .....C-39 18-21 Calibration Results .....C-40-43 22 Projected Peak Water Surface Elevations With Lake Mohave at 647 feet .....C-45 23 Projected Peak Water Surface Elevations With Lake Mohave at 630 feet ................. C-45 24 Hoover Mod Peak Velocities vs. Current Peak Velocities .....C-47 25 Peak Velocities .....C-48 26 Other Alternatives ......C-49 27 Computed Lake Mohave Elevations ......C-50 28 Maximum Possible Reverse Flows ......C-51 29 Storage Provided by Control Dam ......C-52 C-iv TABLE OF CONTENTS (continued) LIST OF TABLES (continued) No. Page 30 Maximum Water Surface Elevations (feet) ............. C-54 31 Minimum Particle Size Required to Armor ............. C-58 32 Tailbay Elevations ................................ C-60 33 Penstock Velocities ................................ C-61 34 Friction Loss Modified Condition ................. C-6I 35 Friction Loss - Uprated Condition ................... C-62 36 Cumulative Head Loss .............................. C-62 37 Capacity Reduction ................................ C-63 38 Penstock Flow Distribution ........................ C-67 39 Water Density ...................................... C-68 40 Upper Limit of Withdrawal Zone for Upper Orifice . C-69 41 Lower Limit of Withdrawal Zone for Upper Orifice . • • C-70 42 Velocity Distribution - Upper Orifice • • • O O O O O C-72 43 Observed Interface Data ............................ C-75 44 Ground Water Conditions at Willow Beach Area ......... C-77 LIST OF FIGURES Following No. Page la River Operation Data Hydrographs - Hoover Dam and Lake Mead ...................................... C-10 lb River Operation Data Hydrographs - Hoover Dam and Lake Mead ..................................... C-10 2a River Operation Data Hydrographs - Davis Dam and Lake Mohave ....................................... C-12 2b River Operation Data Hydrographs - Davis Dam and Lake Mohave ....................................... C-12 C- v TABLE OF CONTENTS (continued) LIST OF FIGURES (continued) Following No. Page 2c River Operation Data Hydrographs - Davis Dam and Lake Mohave ....................................... C-12 3 Hoover Dam Weekly Discharge Schedule - Spring Season . C-12 4 Hoover Dam Weekly Discharge Schedule - Summer Season . C-12 5 Hoover Dam Weekly Discharge Schedule - Fall Season . C-12 6 Hoover Dam Weekly Discharge Schedule - Winter Season . C-12 7a Lake Mead Elevation under 15 Different Hydrologic Sequences (1980-2040) ............................ C-15 7b Lake Mead Elevation under 2 Different Hydrologic Sequences (1980-2040) ........................... C-15 8 Hoover Dam Weekly Load Curve - Summer Season ......... C-26 9 Hoover Dam Weekly Discharge Schedule - Spring Season - Uprated Condition .................................. C-26 10 Hoover Dam Weekly Discharge Schedule - Spring Season . C-26 11 Hoover Dam Weekly Discharge Schedule - Summer Season . C-27 12 Hoover Powerplant Tailwater Curve ................... C-32 13 Colorado River Cross Sections - (22 Drawings) ......... C-34 14 Map of Colorado River Cross Sections C-36 15 Hoover Modification Gage Location Map ............... C-37 16 Hoover Modification Test Release Schedule ........... C-37 17 Colorado River Elevation Gage No. 5 ............... C-38 18 Water Surface Profiles, Lake Mohave at 630 .......... C-43 19 Water Surface Profiles, Lake Mohave at 647 . C-44 20 Water Surface Profiles, Lake Mohave at 630 .......... C-45 21 Water Surface Profiles, Lake Mohave at 630 .......... C-46 C-vi TABLE OF CONTENTS (continued) LIST OF FIGURES (continued) Following No. Page 22 Water Surface Fluctuation at Hoover Tailbay, Lake Mohave at 630 ........................................ C-46 23 Water Surface Fluctuation at Hoover Tailbay, Lake Mohave at 647 ........................................ C-46 24 Water Surface Fluctuation at Willow Beach, Lake Mohave at 630 ... C-46 25 Water Surface Fluctuation at Willow Beach, Lake Mohave at 647 .... C-46 26 Typical Velocity Distribution .....C-47 27 Water Surface Profiles for Other Alternatives .....C-49 28 Water Surface Profiles for Other Alternatives .....C-49 29 Water Surface Profiles for Other Alternatives .....C-49 30 Section for 105' High Cloverleaf Cofferdam No. 3 . C-53 31 A8 and A9 Cofferdam .....C-54 32 Competent Bottom Velocity vs. Transportable Sediment Size .....C-56 33 Tractive Force vs. Transportable Sediment Size .....C-57 34a- Lake Mead Temperature and Conductivity .....C-65 34d 35 Elevation of Intake