Emmanuel Jjunju, Byman Hamududu, Ånund Killingtveit

Transcription

1 Emmanuel Jjunju, Byman Hamududu, Ånund Killingtveit Department of Hydraulic and Environmental Engineering Norwegian University of Science and Technology 21 September 2011

2 Status of Research on Climate Change and Hydropower in Eastern and Southern Africa

3 Outline I Introduction Precipitation projections East Africa Southern Africa Studies on Runoff Runoff: Eastern Africa Runoff: Southern Africa Hydropower General Hydropower: Eastern Africa Southern Africa Conclusions GCMs, Scenarios and Models

4 fl Introduction Ug an da Democratic Repub lic of Congo Kenya Tanzania Angola Zambia Mo z am biq ue Based on a review of works related to climate change and hydropower Predictions for precipitation, temperature,rainfall and runoff? Which GCMs,cenarios and Models were applied? What Conclusions can be drawn Zimbabwe Namibia Botswana South Africa Figure 1: Study Area

5 IPCC Projections: Eastern Africa To: ipcc Positive shift of rainfall distribution during the wet seasons Increase in mean precipitation rates and intensity of extreme events General agreement between IPCC AR4 models (Shongwe et al. 2010; IPCC 2007)

6 IPCC Projections: Southern Africa To: ipcc Dominated by decreases in Annual precipitation Some precipitation increases in northern Zambia, Malawi, and Mozambique Increase in the severity of dry extremes.i.e. More severe droughts (West-Southern Africa) Delay in onset of the rainy season(entire Southern Africa) Shorter rain Season(entire Southern Africa) (Shongwe et al. 2010; IPCC 2007)

7 Runoff: General Projections I Changes based on statistically derived runoff from GCM ensemble mean of scenario A1B (Milly et al. 2005) increases of 10% to 40 % in eastern Equatorial Africa decreases between 10% to 30% in Southern Africa Figure 2: Projected change in annual runoff volume by 2050s relative to 1900 to 1970.(Milly et al. 2005)

8 Changes in Precipitation (%) Runoff: Eastern Africa I Nile Basin (Booij et al. 2011) Used HBV & RIBASIM(a water distribution and allocation model) Three GCMs and Two SRES scenarios Large differences in future climate and discharges for different GCMs. Study Stations Mongolla Deim Atbara HIGH LOW Figure 3: Average GCM simulated changes (2065) in annual rainfall (Booij et al. 2011)

9 Runoff: Southern Africa I Thukela River Basin, KwaZulu-Natal, South Africa (Graham et al. 2011) Multiple model projections to asses impact on Runoff Statististical Downscaling(SD) with CGCM,CNRM, ECHAM5,GISS,IPSL (A2) up to 2100 Regional Climate Model(RCA3 from Rossby Centre) bounded by CCSM-B2, ECHAM4-B2 & A2, CCSM-A1b and EcHAM5-A1b (1961 to 2050) ACRU hydrological model SD showed annual increase in rainfall and runoff

10 Runoff: Southern Africa I Zambezi Basin wide study(beck and Bernauer 2011) Used a number of water use scenarios Scenario considered demand and supply side changes including climate changes All scenarios show decreases. Scenarios with climate change have higher decreases (Table 5 shows the flows at country level) Decreases in absolute amounts for all countries and in share for upstream countries.

11 Country variable variable y2000 y2000_perc cumecs 1000 Scen1 Scen2 perc 20 Scen1_perc Scen2_perc Scen3 Scen3_perc Zimbabwe Zambia Tanzania Namibia Mozambique Malawi Botswana Angola Zimbabwe Zambia Tanzania Namibia Mozambique Malawi Botswana Angola Country Figure 4: Mean flows [m3/s] by country projected for 2050 (October) Figure 5: change [%]in share by country projected for 2050 (October)

12 Runoff: Southern Africa Limpopo basin projections 5 to 15% decrease in rainfall 5 to 20% increase in Evaporation 25 to 35% decrease in streamflow (Desanker and Magadza, 2001).

13 Hydropower: General Comments I Few Published Studies focusing on hydropower in the region Climate Change Assessments begnning to be incorporated in Hydropower studies e.g. NELSAP (NBI 2005) Focus has been dominated by impacts on hydropower and of hydropower as a part of the water demand Adaptive potential of hydropower rarely examined e.g control of floods and storage of water to deal with changing regimes.

14 Hydropower: Eastern Africa I Nile Basin Capacity Building Network study of Lake Victoria Basin (Kizza et al. 2010) Tested the impact of climate change using hydropower sites on the Kagera and Mara catchments. Applied what-if scenarios of temperature and rainfall change Scenarios: +3 o C and +10 or 20 or 30%, Precipitation based on observed trends (Kizza et al. 2009) Used SWAT Model (not always good fits especially in Kagera)

15 Hydropower: Eastern Africa II "+20%" "+10%" Goronga Machove Kilgoris Kikagate Baseline Rusumo "-10%" "-20%" -80% -60% -40% -20% 0% 20% 40% 60%

16 Hydropower: Southern Africa I Zambezi (Yamba et al. 2011) GCMs: CCCMA HADCM3 and CSIRO (Scenario A2) WRSM Model (Pitman) Extreme events (both wet and dry) to increase General tendecy for reductions Declining storage levels Figure 6: Gross theoretical hydroelectric power potential for existing Cahora Bassa

17 Conclusions I Most studies indicate reductions in water resources in southern Africa and increases in Eastern Africa Most of them use A2 or A1B scenarios Many include an assessemnt of GCM performance Majority of studies focus on Precipitation and Water Resources in general (incorporating subjective Demand scenarios) Few studies driven by hydropower or highlighting the positive contributions of hydropower to adaptation (water security)

18 Conclusions II Many important hydropower basins (e.g Congo) still not having comprehensive studies. Ranges of changes may not always agree but the sign of chnage agrees in most studies

19 Thank You For Listening Questions?

20 FIGURES

21 Figure 7: Temperature and precipitation (Africa); MMD-A1B; IPCC vs Back:Eastern Africa Back:Southern Africa

22 Nile Catchments in Booij et al. (2011) Back

23 References Lucas Beck and Thomas Bernauer. How will combined changes in water demand and climate affect water availability in the zambezi river basin? Global Environmental Change, 21(3): , ISSN doi: DOI: /j.gloenvcha URL Symposium on Social Theory and the Environment in the New World (dis)order. Martijn J. Booij, Daniel Tollenaar, Eelco van Beek, and Jaap C.J. Kwadijk. Simulating impacts of climate change on river discharges in the nile basin. Physics and Chemistry of the Earth, Parts A/B/C, In Press, Corrected Proof:, ISSN doi: DOI: /j.pce URL L. Phil Graham, Lotta Andersson, Mark Horan, Richard Kunz, Trevor Lumsden, Roland Schulze, Michele Warburton, Julie Wilk, and Wei Yang. Using multiple climate projections for assessing hydrological response to climate change in the thukela river basin, south africa. Physics and Chemistry of the Earth, Parts A/B/C, (0):, ISSN doi: /j.pce URL IPCC. Climate Change 2007: The Physical Science Basis. Cambridge University Press, July ISBN Michael Kizza, Allan Rodhe, Chong-Yu Xu, Henry K Ntale, and Sven Halldin. Temporal rainfall variability in the lake victoria basin in east africa during the twentieth century. Theoretical and Applied Climatology, 98(1-2): , URL