Design Considerations for Addressing Climate Change Vulnerabilities of Dams and Reservoirs

Transcription

1 Design Considerations for Addressing Climate Change Vulnerabilities of Dams and Reservoirs

2 Agenda Introduction Dam and Reservoir Vulnerabilities Decision Process Risk Review Case Study Candidates Lesotho Highlands Project Preliminary Observations Next Steps 2

3 Likely Scenarios if CC Continues Graphic adapted from the National Geographic Society web-site accessed Feb 12,

4 Projected Exposure to Change in Runoff Graphic adapted from Strzepek and Yates,

5 Dam and Reservoir Vulnerabilities DAM AND RESERVOIR COMPONENTS Basin Yield Reservoir Size Hydro Power Output Irrigation or Water Supply Water Quality Spillway Design Discharge Outlet Works River Diversion HYDROLOGICAL DRIVERS Average Annual Precipitation (AP) Precipitation Extremes (EP) Glaciers and Snow (GS) Sea Level (SL) Evapotranspitation (ET) Soil Moisture (SM) Runoff and River Discharge (RR) 5

6 Typical Dam & Reservoir Project Life Cycle Operation Ability to Influence Design Construction Planning Time 6

7 Stakeholder Influence Planners Ability to Influence Regulators Beneficiaries Designers Financiers Owners Operators Planning Design Construction Operation 7

8 Decision Process High Planners & Regulators Owners & Financiers Owners & Designers Operators & Designers Regulators & Financiers Financiers & Beneficiaries Ability to Influence Low Moderate Operators, Financiers Owners, Designers Operators, Designers Planners, Regulators Operators, Planners, Regulators Financiers Planners, Financiers Owners, Regulators Owners, Designers Operators, Planners Owners, Regulators Operators, Designers, Planners Policy Economics Risk Technology Environmental Social 8

9 Risk Management Strategy Planning Ability to Influence Maximize use of modeling to examine likely futures Seek and apply new technologies and management methods to ensure that system functions can be maintained with changing circumstances Adaptive Understand changing circumstances and needs and apply new operational rules Revise operation or implement physical changes so the system delivers acceptable levels of service or management over a range of conditions Project Life Cycle Planning & Design Construction Operation 9

10 Risk Profile Yield High Severity Environment Hydro Low Probability Moderate 10

11 Economic Impacts of CC on a Dam Project 11

12 Case Study Candidate Projects Dam and Reservoir Project Components Case Study Projects Basin Yield Reservoir Size Hydro Power Output Irrigation or Water Supply Water Quality Spillway Design Discharge Outlet Works River Diversion Lesotho Highlands AP, ET, SM, RR AP, ET, SM, RR AP, ET, SM, RR AP, ET, SM, RR AP, ET, SM, RR EP EP EP Siberian River Reversal Possible case study Salt River Project Possible case study AP - Average Annual Precipitation Hidrovia Navigation Possible case study EP - Precipitation Extremes Kafue Gorge Lower Hydro Nam Theun 2 Hydro Yacyretá Kárahnjúkar Hydro Possible case study Possible case study Possible case study Possible case study GS - Glaciers and Snow SL - Sea Level ET - Evapo-transpitation SM - Soil Moisture RR - Runoff and River Discharge 12

13 Lesotho Highlands Water Project Phase 1A Katse Dam, Muela Powerstation (72 MW), Transfer Tunnel (45km) from Katse to Muela PS, Muela Dam, Delivery Tunnel (36km) from Muela Dam to Axle River Outlet Phase 2 Mashai Dam, Pumping station connecting Mashai and Katse reservoirs, 2 nd transfer tunnel from Katse to Muela, 2 nd delivery tunnel from Katse reservoir to Axle River Outlet Phase 1B Mohale Dam, Transfer Tunnel (30 km) from Mohale to Katse Reservoir, Matsoku diversion and transfer tunnel (6.4 km) to Katse, increased capacity of Muela PS (110 MW) Phase 3 Tsoelike Dam, Pumping Station connecting Tsoelike and Mashai reservoirs Phase 4 Ntoahae Dam, Pump station connecting Ntoahae and Tsoelike reservoirs 13

14 Areas of Vulnerability Related to Purpose Yield at Katse Dam to support water deliveries Hydropower production from water deliveries A secondary function Sizes of intermediate storage reservoirs Vaal and Muela reservoirs Demands Larger or lower than expected growth 14

15 Candidate mitigating strategies to prepare for a declining yield trend project planning phase Plan for future off-stream storage A staged approach Plan for dam raising Dam design and reservoir planning Consider options for conjunctive ground surface water storage and operation River basin management to discourage practices reducing runoff 15

16 Areas of Vulnerability Related to Safety or Other Factors Spillway discharge capability Reservoir freeboard Outlet works design Construction diversion facilities Environmental flows 16

17 Candidate mitigating strategies to prepare for extreme events - project planning phase Plan for supplemental spillway capacity - overflow section or emergency spillway (future action) Increase flood storage capability using parapet wall (future action) Plan for future parallel outlet tunnel (future action) Diversion arrangement and dam type selection (near-term action) Use of more conservative design parameters (nearterm action) 17

18 Preliminary Observations Issues: (1) Project Safety and (2) Performance Planning and design standards and procedures Flexibility; not foreclosing future options Economics is it worthwhile to invest? Avoid over-reliance on one source or technology 18

19 Next Steps Continued project review / case study analysis Requirements for guide specifications in Bank lending TORs 19

20 Thank you for your attention 20