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CLIMATE CHANGE AND WATER RESOURCES: CHALLENGES AND QUESTIONS FOR THE D.W.A.F.

CLIMATE CHANGE AND WATER RESOURCES: CHALLENGES AND QUESTIONS FOR THE D.W.A.F. Roland Schulze Professor of Hydrology. School of Bioresources Engineering and Environmental Hydrology University of KwaZulu-Natal, Pietermaritzburg. THE BASIC PREMISE . . .

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CLIMATE CHANGE AND WATER RESOURCES: CHALLENGES AND QUESTIONS FOR THE D.W.A.F.

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  1. CLIMATE CHANGE AND WATER RESOURCES: CHALLENGES AND QUESTIONS FOR THE D.W.A.F. Roland Schulze Professor of Hydrology School of Bioresources Engineering and Environmental Hydrology University of KwaZulu-Natal, Pietermaritzburg

  2. THE BASIC PREMISE . . . Climate change is a global phenomenon, but the problems will be very local and we will have to adapt and plan

  3. WHAT DO WE HAVE TO CONSIDER IN THE WATER RESOURCES SECTOR IN REGARD TO CLIMATE CHANGE? (a) The water sector is an integrating, cross- cutting one

  4. - INTEGRATED IMPACT ASSESSMENT - Global Regional Local Sectoral coastal agriculture health

  5. WHAT DO WE HAVE TO CONSIDER IN THE WATER RESOURCES SECTOR IN REGARD TO CLIMATE CHANGE? (b) The hydrological cycle amplifies any changes in rainfall[PMG note: maps not incuded, please email info@pmg.org.za]

  6. WHAT DO WE HAVE TO CONSIDER IN THE WATER RESOURCES SECTOR IN REGARD TO CLIMATE CHANGE? (c) Climate change scenarios have to be downscaled to the scale at which DWAF operates[PMG note: maps not incuded, please email info@pmg.org.za]

  7. The Challenge: GCM RCMQC HRU[PMG note: maps not incuded, please email info@pmg.org.za]

  8. WHAT DO WE HAVE TO CONSIDER IN THE WATER RESOURCES SECTOR IN REGARD TO CLIMATE CHANGE? (d) Climate change impacts have to address key issues of the National Water Act

  9. Hillslope and Riparian Zone Processes in ACRU (after Meier et al., 1997; Schulze, 2000b)

  10. VARIABLE AREA OF OPEN WATER WATER SURFACE EVAPORATION UPSTREAM INFLOWS TRIBUTARY INFLOWS CHANNEL STORAGE AND ROUTING DRAINAGE AND ABSTRACTIONS TOTAL EVAPORATION PERIODICALLY SATURATED TOPSOIL HORIZON SATURATED SUBSOIL HORIZON VARIABLE WATER-SOIL INTERFACE WETLAND SPILLWAY IMPERVIOUS LAYER Concepts, Processes and Assumptions in the ACRU Wetlands Module (after Schulze et al., 1987; with modifications by Schulze, 2001d)

  11. Schematic of Irrigation Water Demand and Scheduling Options Available in ACRU (after Schulze, 1995 and updates)

  12. WHAT HAVE FIRST RESULTS FROM THE W.R.C. PROJECT ON CLIMATE CHANGE AND WATER RESOURCES IN SOUTH AFRICA SHOWN?

  13. DETAIL “EXPLODES” FROM ANNUAL TO MONTHLY TO DAILY VALUES: TEMPERATURE [PMG note: maps not incuded, please email info@pmg.org.za]

  14. DETAIL “EXPLODES” FROM ANNUAL TO MONTHLY TO DAILY VALUES: RAINFALL [PMG note: maps not incuded, please email info@pmg.org.za]

  15. Potential Evaporation is Projected to Increase by 10 - 20% Implications: Enhanced dam evaporation losses Increased irrigation demands [PMG note: maps not incuded, please email info@pmg.org.za]

  16. Soils are Projected to Become Drier More Often Implications: Reduced runoff per mm rainfall Land use changes Reduced crop yields Higher irrigation demands [PMG note: maps not incuded, please email info@pmg.org.za]

  17. Fewer, but larger rainfall events may result in more groundwater recharge [PMG note: maps not incuded, please email info@pmg.org.za]

  18. Shifts in the Distribution of Runoff are Projected to Occur Implications: Reservoir operating rules change Ecological reserve (IFRs) change [PMG note: maps not incuded, please email info@pmg.org.za]

  19. Implications to Irrigation are Likely to be Significant [PMG note: maps not incuded, please email info@pmg.org.za]

  20. WHAT COULD THIS IMPLY IN AN ACTUAL CATCHMENT SITUATION? A case study from Swaziland

  21. MBULUZI : CONFIGURATION 1 2 Irrigation – Local Supply Irrigation – Mnjoli Dam 3 Irrigation – Inter Basin Transfers 4 Irrigation – Multiple Sources 5 Inter Basin Transfers 6 21 Reservoir 7 12 Streamflow Gauge 8 9 14 22 23 11 16 13 10 25 15 18 Mnjoli 17 19 24 26 32 20 34 33 27 28 29 30 31 35 36 39 40 37 38

  22. DRY YEAR AVERAGE YEAR POTENTIAL IMPACTS OF CLIMATE CHANGE, MBULUZI CATCHMENT (Scenario: T = T + 2°C; P = P – 10%) MNJOLI DAM: % OF FULL SUPPLY CAPACITY

  23. POTENTIAL IMPACTS OF CLIMATE CHANGE, MBULUZI CATCHMENT (Scenario: T = T + 2°C; P = P – 10%) MBULUZI OUTFLOWS TO MOZAMBIQUE AVERAGE YEAR DRY YEAR

  24. WHERE TO NOW? THE NEED TO ADAPT IN WATER RESOURCE MANAGEMENT

  25. THE ADAPTATION PROCESS • Acess to information AWARNESS • Experiences of threat OF THREAT • Sensitivity to threat • External influences of regulations/ wealth - Government INTENTION - CMAs/ Water Boards TO ADAPT - State of economy • Internal characterstics - Institutional capacity/ will ACTIVE ADAPTATION • Range of options - Demand - Supply - Culture - Expectations After Arnell (2005)

  26. Trends may shift beyond thresholds Variability may increase beyond thresholds Thresholds may decrease

  27. DECISION FRAMEWORK ON CLIMATE VARIABILITY AND CLIMATE CHANGE • Supply demand • Reservoir safety • Reservoir sizing • Land management • Operating rules • Water orders • Water allocation • Demand management • Irrigation scheduling • Flood warning • Field operations

  28. S.A. ADAPTATION FRAMEWORK: CLIMATE CHANGE IMPACTS ON THE WATER SECTOR

  29. BUT . . . IS IT AS SIMPLE AS ALL THAT? NO, BECAUSE . . . (a) Climate change also means land use change

  30. BUT . . . IS IT AS SIMPLE AS ALL THAT? NO, BECAUSE . . . (b) Hydrological baselines against which SFRAs are levied, will shift[PMG note: graphics not incuded, please email info@pmg.org.za]

  31. BUT . . . IS IT AS SIMPLE AS ALL THAT? NO, BECAUSE . . . (c) “Hotspots” of climate change concern may need priority attention by DWAF

  32. Runoff-Producing Stormflow Events are Projected to Change Implications: Lower inflows into reservoirs in certain areas Catchment sediment yields will change

  33. BUT . . . IS IT AS SIMPLE AS ALL THAT? NO, BECAUSE . . .(d) Impacts of climate change on the water sector may be felt sooner than we like[PMG note: maps not incuded, please email info@pmg.org.za]

  34. BUT . . . IS IT AS SIMPLE AS ALL THAT? NO, BECAUSE . . . (e) Climate change impacts will be superimposed on already existing complex land use impacts[PMG note: maps not incuded, please email info@pmg.org.za]

  35. BUT . . . IS IT AS SIMPLE AS ALL THAT? NO, BECAUSE . . . (f) The ecological “Reserve” will be impacted

  36. The aquatic environment is a LEGITIMATE water user and NOT a competing resource Upstream and downstream ecosystems management will have to adapt with climate change[PMG note: graphics not incuded, please email info@pmg.org.za]

  37. BUT . . . IS IT AS SIMPLE AS ALL THAT? NO, BECAUSE . . . (g) Health services will be impacted

  38. BUT . . . IS IT AS SIMPLE AS ALL THAT? NO, BECAUSE . . . (h) Water quality will be impacted  Chemical  Physical  Biological[PMG note: graphics not incuded, please email info@pmg.org.za]

  39. BUT . . . IS IT AS SIMPLE AS ALL THAT? NO, BECAUSE . . . (i) Water availability to the poor will be impacted [PMG note: graphics not incuded, please email info@pmg.org.za]

  40. BUT . . . IS IT AS SIMPLE AS ALL THAT? NO, BECAUSE . . . (j) International water agreements with our neighbouring countries may have to be re-negotiated

  41. THE TAKE-HOME MESSAGE. . Climate change is a global phenomenon, but the problems will be very local and we will need to adapt and plan

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