FLOOD CONTROL CHALLENGES FOR LARGEHYDROELECTRIC RESERVOIRSEXAMPLE FROM NAM THEUN-NAM KADING BASIN IN LAO PDRPeter R.B. War...
Flood Control for Large Reservoirs:         Design and Operation• Climate and Expected Large Flood Events• Storage for Flo...
Flood Control for Large Reservoirs:      Design and Operation
Flood Control for Large Reservoirs:      Design and Operation
Thailand Examples                                      UBOL RATANA DAMSRINAGARIND DAM
Srinagarind Dam, Thailand
Srinagarind Dam, Thailand
Ubol Ratana Dam, Thailand• 1966 Dam commissioned, primarily for storage for agriculture• 1978 Disaster narrowly averted wh...
Nam Theun River Basin: overview• Difficult climate: periodic extremely heavy rain events associated  with tropical cyclone...
Nam Theun River Basin:hydropower development
Nam Theun River basin:hydropower development
Table 1. Main characteristics of Theun-Hinboun, Nam Theun 2 and Nam Gnouanghydropower projects. Data from Then-Hinboun are...
Nam Theun: river flow      Peak: 18,000 m3/s   Peak: 9,000 m3/s
Nam Theun: peak flow events  Two largest events in 10 year daily record: Theun Hinboun damsite
Nam Theun: typhoon tracks                            Typhoon tracks                            2002 (left) and            ...
Nam Theun: Water balance• We used simple model for NT2 reservoir, with computed  inflows based on flow data before and dur...
Nam Theun:         simulated reservoir storageNT2 reservoir water surface during typhoon induced major runoff eventAll gat...
Nam Theun:              simulated reservoir storageToo-little-too-late operation. One spillway gate not functioning, and d...
Nam Theun: conclusions• We concluded that a great deal of care and a very  tight requirement for timely response is needed...
Nam Theun: Recommendations1.   Adherence to a well conceived rule curve for reservoir surface     levels in the flood seas...
Nam Theun: RecommendationsSuggestions are made for• the establishment of a strengthened capacity for the  NT-NK River Basi...
• Ongoing research work on climate periodicities in  the Mekong region is encouraging, as it promises  to offer ways of ac...
Flood Control for Large Reservoirs:   Design and Operation    Thank you for your attention                      Thank you ...
Columbia River Treaty• 11 years of discussions post 1948.• Ratified in 1964 for 60 year period. 10 year prior notification...
Srinagarind Dam, Thailand• Periodic extremely heavy rain events, determined by monsoon  conditions, and weather associated...
Flood Control for Large Reservoirs:      Design and Operation
Flood Control Challenges for Large Hydroelectric Reservoirs
Flood Control Challenges for Large Hydroelectric Reservoirs
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Flood Control Challenges for Large Hydroelectric Reservoirs

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Presentation from Session 4: Food, Water and Energy in Catchments

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Flood Control Challenges for Large Hydroelectric Reservoirs

  1. 1. FLOOD CONTROL CHALLENGES FOR LARGEHYDROELECTRIC RESERVOIRSEXAMPLE FROM NAM THEUN-NAM KADING BASIN IN LAO PDRPeter R.B. Ward, Timo A. Räsänen, Peter-John Meynell, Tarek Ketelsen, Khamfeuane Sioudomand Jeremy Carew-ReidCHALLENGE PROGRAM ON WATER & FOOD IN THE MEKONG: Optimizing the management of hydropower cascades at the catchment level (MK3)
  2. 2. Flood Control for Large Reservoirs: Design and Operation• Climate and Expected Large Flood Events• Storage for Flood Pulse Modulation• Spillway Flow Capacity and Operation• Mechanical Reliability and Servicing
  3. 3. Flood Control for Large Reservoirs: Design and Operation
  4. 4. Flood Control for Large Reservoirs: Design and Operation
  5. 5. Thailand Examples UBOL RATANA DAMSRINAGARIND DAM
  6. 6. Srinagarind Dam, Thailand
  7. 7. Srinagarind Dam, Thailand
  8. 8. Ubol Ratana Dam, Thailand• 1966 Dam commissioned, primarily for storage for agriculture• 1978 Disaster narrowly averted when a flood overtopped the core of the dam by 24 cm. Average daily peak inflow more than triple the designed maximum spillway capacity.• Original design flood estimate was insufficient.• Outcome:• EGAT began formal dam safety practices, such as comprehensive dam safety reviews, emergency preparedness• 1986-7 Dam was raised by 3.1 m, and spillway capacity was increased by 40%. Additional work cost $15 million, an outlay of 70% on top of the original cost.
  9. 9. Nam Theun River Basin: overview• Difficult climate: periodic extremely heavy rain events associated with tropical cyclone weather: typhoons and tropical storms. Global climate change promises more extreme future weather.• Short number of years for hydrological data set for the basin: design risk• Three projects in operation, and others proposed• Dams are not owned by one entity, communications question• Nam Theun 2 flow scheduling and reservoir operation is done from another country
  10. 10. Nam Theun River Basin:hydropower development
  11. 11. Nam Theun River basin:hydropower development
  12. 12. Table 1. Main characteristics of Theun-Hinboun, Nam Theun 2 and Nam Gnouanghydropower projects. Data from Then-Hinboun are before the (2012) expansion project Theun-Hinboun Nam Theun 2* Nam GnouanDam height [m] 27 39 67Active storage [mcm] 15 3530 2260Flood buffer [mcm] 1410 470Reservoir drawdown [m] 5 12.5 35Surface area at FSL [km2] 6.3 450 107Average discharge [m3/s] 220 (460 before NT2) 240 95Catchment area [km2] 8937 4013 2942Installed capacity [MW] 210 to be enlarged 1090 60Head [m] 230 348 47Turbine discharge [m3/s] 110 330 144Annual production [GWh] 1356 (1645 after NG) 5936 294Spillway type 2 radial gates 5 radial gates (1374 5 radial gates 3 3 3 (1160m /s/gate); 1 flap m /s/gate ); 2 flap gates (3144 m /s/gate) 3 3 gate (50m /s); 4 sand (192m /s/gate) flushing gates (20m3/s/gate); fixed overflow weirSpillway capacity [m3/s] 12500 6870 15700* Data are for Nakai Dam on Nam Theun River. Reservoir is also contained by an (earth)saddle dam, on the south side.
  13. 13. Nam Theun: river flow Peak: 18,000 m3/s Peak: 9,000 m3/s
  14. 14. Nam Theun: peak flow events Two largest events in 10 year daily record: Theun Hinboun damsite
  15. 15. Nam Theun: typhoon tracks Typhoon tracks 2002 (left) and 2011 (right) Sept and Oct
  16. 16. Nam Theun: Water balance• We used simple model for NT2 reservoir, with computed inflows based on flow data before and during the 2002 extreme flood event, to check on reservoir water surface heights. Peak inflow on 22nd Sept was 12,000 m3/s.• We wanted to see what would happen during a “Normal” procedure, and a “Too little too late” procedure for operating the spillway gates.• We assumed that at the start of the extreme runoff event the reservoir was full to the FSL, and that there was still available the (large) flood buffer storage above this level.
  17. 17. Nam Theun: simulated reservoir storageNT2 reservoir water surface during typhoon induced major runoff eventAll gates at Nakai dam working, and timely response
  18. 18. Nam Theun: simulated reservoir storageToo-little-too-late operation. One spillway gate not functioning, and delayedmaximum opening of other gates. Dangerously high water level in reservoir.
  19. 19. Nam Theun: conclusions• We concluded that a great deal of care and a very tight requirement for timely response is needed at NT2 dam, even for management of a flood event (10 year event?) that is not extreme.• Not clear how future exceptional flood events will be managed successfully.• Need for a variety of management/governance/co-ordination activities.
  20. 20. Nam Theun: Recommendations1. Adherence to a well conceived rule curve for reservoir surface levels in the flood season, with periodic updating of the rule curve to reflect improved knowledge of the basin, and long term shifts from climate change2. Ready access to long term and short term weather predictions, particularly for heavy rain expected from typhoon events.3. Responsiveness to daily and hourly developments during major floods4. Periodic comprehensive dam safety reviews, by an independent team that should include engineering experts, with backgrounds in hydrology, geotechnology, mechanical engineering and electrical engineering.
  21. 21. Nam Theun: RecommendationsSuggestions are made for• the establishment of a strengthened capacity for the NT-NK River Basin Committee Secretariat• emergency communications capability between stakeholders, e.g. dam operators and downstream stakeholders• periodic, long-term requirements for engineering assessment concerning safe operations at the dams.
  22. 22. • Ongoing research work on climate periodicities in the Mekong region is encouraging, as it promises to offer ways of achieving advance notice of the likelihood of an extreme weather season.• Links between the WNPM, ENSO and PDO events is being established, and this understanding will provide extremely helpful with advanced warning and preparedness.
  23. 23. Flood Control for Large Reservoirs: Design and Operation Thank you for your attention Thank you for your attention
  24. 24. Columbia River Treaty• 11 years of discussions post 1948.• Ratified in 1964 for 60 year period. 10 year prior notification before expiry• Basic idea was to construct and operate four projects (3 in Canada) that would achieve hydropower generation and flood control.• Several downstream projects in the US benefit from the upstream Treaty projects with the ongoing benefit of generating more HP energy• Treaty covers Canadian entitlement “one half of the estimated increase in US downstream power benefits”
  25. 25. Srinagarind Dam, Thailand• Periodic extremely heavy rain events, determined by monsoon conditions, and weather associated with tropical cyclone activity• Short data set available when design was undertaken (early 1970s).• Design flood selected, and spillway size with operating procedures determined. Construction was delayed, and dam finally completed in 1980.• 18 years later, review of hydrological conditions, spillway capacity shown to be less than desirable.• Decision made to operate the reservoir with a different set of RULE CURVES, for dam safety reasons.
  26. 26. Flood Control for Large Reservoirs: Design and Operation
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