Rudo Sanyanga Africa Program Director International Rivers South Africa

Transcription

1 Rudo Sanyanga Africa Program Director International Rivers South Africa

2 Assessing Risks, Uncertainty and Consequences of Hydro-dependent Systems on the Zambezi River Basin

3 Overview of the Zambezi Hydrology The Zambezi has 13 subbasins (sbs). Upper Zambezi (6 sbs) Wettest region mm mean rainfall Ext. Flood plains Middle Zambezi-(4 sbs) Hot and dry 900 mm mean rainfall, ext high evapo losses Lower Zambezi- (3 sbs)1000mm mean rainfall

4 The Zambezi & Climate Change Climate models forecast less rain and higher temperatures for Sub-Saharan Africa in the next 50 years. The Hydrology of the Zambezi River basin will become much more variable, with less rainfall, more droughts, extreme weather, reduced flow

5 Hydro-dependency risks Many Sub Saharan African nations are more than 60% hydrodependent ( excluding SA). Rising droughts +hydrodependency = blackouts and economic disruptions Ex 1. Kenya is 66% hydrodependent. In 2011, a 90 MW shortfall in power due to drought forced Kenya to replace lost hydro with expensive emergency generators. E x 2 Tanzania cut its GDP growth due to HEP drought induced shortfalls Ex 3 Burundi currently faces 8- megawatt power deficit due to drought.

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7 Potential Evaporation rates are higher than rainfall in all of the subbasins

8 Main features of the Zambezi ter Management Basin hydrology insadc ANDFLODRELEASESIN VERBASINPROJECT The most variable river basin in the world Average rainfall 960mm; range mm per year Average potential annual evaporation 1870mm exceeds rainfall Vast flood plains delay discharge Extreme droughts and floods are a regular feature Prolonged periods of below average and above average rainfall

9 Climate change predictions in basin Temperature Increased temperature and evaporation o C per decade Increase in potential and open water evaporation Significant increase in evapo-transpiration (10-25% over the next century) and decrease in humidity Based on IPCC ( 2001,2007) and KNMI (2007)

10 Climate change predictions in basin Rainfall Reduced rainfall Reduction in annual ppt (10-15% less, less rainfall days and average intensity) over the basin Increased inter-annual variability with higher rainfall anomalies and more intense widespread droughts Greater chance of heavy rainfall events in Angola, Namibia, Mozambique, Malawi & Zambia

11 Climate change predictions in basin Runoff Reduced runoff 10% decrease in rainfall causing 17% reduction in runoff from 1000mm regions and 50% reduction in regions of 500mm regions per annum All Zambezi basin countries reduction in stream flow 16% reduction in Upper Zambezi, 24-34% in Middle Zambezi & % in Lower Zambezi

12 mpact of Climate Change on Reservoirs Reservoirs are affected by CC in at least 5 ways 1. Reduced reservoir inflows due to reduced run-off 2. Increased extreme flooding (Inflows) events 3. Shift in the timing of the wet season flows, delayed onset of rainy season 4. Increased surface water evaporation, increase in temperatures 5. Increased sediment load to reservoirs, due to higher rainfall intensity and corresponding erosion

13 Economic Risks associated with reduced mean annual flows Over estimation of firm power generation Predictions estimate a drop of 32% from 30,013 to 20,270 GWh per yr Reduced revenue from total energy production and other uncertainty Drop of 21% from 55,857 to 44,189 GWh per year Reduced revenue for downstream industry who may in turn reduce production due to reduced power Both Mphanda Nkuwa and Batoka assume stationarity of historic mean and variability of flow. CC modeling for Batoka show flow reduction of 10-35% resulting in monthly generation drop of 6-22%

14 Conclusions Providing for the Future Future hydropower development on the Zambezi basin is extremely risky from a hydropower and financial perspective. Planning for hydropower must take into account hydrological risks to help make the Zambezi basin countries less vulnerable to climate change and improve the energy security. Despite uncertainties about climate, we know enough to act. New Scientist 2009

15 Adapting Hydropower systems to reduce economic risks of CC Incorporate climate change scenarios into hydropower design and operation Assess hydropower in the context of comprehensive basin-wide planning Develop strong institutional capacity for water resources management Diversify the regional power pool to reduce hydropower dependency

16 Adapting Hydropower systems & energy to reduce economic risks of CC- cont.. Improve existing hydropower capacity rather than investing in new infrastructure Improve monitoring and evaluation to adapt dammanagement to a changing climate Develop and implement alternative sustainable energy policies Solar power in an 0ff-grid village in Nepal. Photo: Alex Zahnd

17 Mamelodi (Pretoria) Solar heater development

18 Further Information Hydrorisk and Large Hydropower on the Zambezi River basin Please contact: Thank you!