1. Water Balance Model of Lake Malawi and its Sensitivity to Climate Change
Dr Patsani G Kumambala (LUANAR)
Late Prof Alan Ervine (University of Glasgow)

2. Presentation Layout Introduction Methodology Results
Summary and Conclusion
Recommendations

3. Facts behind Lake Malawi and Shire river system
INTRODUCTION
Facts behind Lake Malawi and Shire river system
Lake Malawi and the Shire river system play a major role in Malawi’s economic sector.
Hydropower stations along the Shire river
The Shire is the main source of water for the country’s largest sugar plantation at Nchalo and other irrigation schemes in the Lower Shire Valley (LSV)
Water supply to the city of Blantyre
The lake also serves as a medium for water transportation
Lake Malawi is also recognized as a world heritage site as it is home to an estimated 500 – 1000 fish species
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5. Facts behind water levels of Lake Malawi
INTRODUCTION
Facts behind water levels of Lake Malawi
In 1915 and 1935 there was no outflow from the lake into the Shire river
The lowest lake level of 469 m above sea level was experienced in 1915
The highest lake level of 477 m above sea level was experienced in 1980
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6. Why WBM with Climate Change?
One of the major challenges facing the sustainability of water resources is climate change
observed climate changes are evidenced by
the changes in the rainfall season, pattern and temperature, and changes in the frequency of droughts and floods
As well as significant variations in Lake Malawi and river levels
Necessary to combine studies of water balance model with studies of climate change effects on the water resources if sustainability of water resources is to be maintained
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7. Components of Lake Malawi Water Balance Model
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8. WATER BALANCE MODEL EQUATIONcc
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Inflow into the Lake
Runoff inflow into Lake Malawi is a combination of the runoff records from all the major catchments in Malawi, Tanzania and Mozambique
Malawi contributes the lion share of the land catchment of 66,810 km2 (68.35%), seconded by Tanzania with 25,470 km2 (26%) and Mozambique km2 (5.58%)
Tanzania contributes the lion share of water inflow into the lake (55%)
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10. Inflow into the Lake – Catchment contribution
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Correlation of Lake Malawi water levels and outflows at Mangochi station
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12. Correlation of Lake Malawi water levels and outflows
General Equation of Lake outflow
Lake Malawi outflow equation
The constant varies between 0 and 3 in many natural lakes. The value is always equal to 1 when there is a linear relationship between effective head and lake levels
The “b” value in equation 5 indicates that a small change in lake level would have a significant effect on the lake outflow.
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13. Calibration of Lake Outflow Equation
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14. Water Balance Model Calibration and verification
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15. Water Balance Model Calibration and verification
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16. LAKE LEVEL AND OUTFLOW SENSITIVITY TO CLIMATE CHANGE
rain- fall and evaporation are the major components of the WBM. Any change in these two major components could have an adverse impact on the water level of Lake Malawi.
Rainfall is the component which varies most while evaporation varies least.
Need to analyse lake level and outflow sensitivity to climate change based on projected changes in the water bal- ance model components.
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17. Climate Data for Future Scenarios
General circulation models (GCMs) for simulating future climate data for temperature and rainfall were obtained from the United Kingdom (UK) Meteorological Office Hadley Centre
GCM data from Hadley Centre are derived from UK Meteorological Office coupled ocean-atmosphere GCM (HadCM3) experiments and normalized over the period 1961 – 1990
GCM outputs from the UK HadCM3 experiments derived based on different emission scenarios have a coarse resolution.
Downscaling GCM outputs to the required area utilizing SDSM Model (a hybrid of stochastic weather generators and regression based techniques used to linearly correlate large scale GCM parameters to local scale weather generator parameters such as rainfall occurrence and intensity)
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18. IPCC Emission Scenarios
According to IPCC (2007), scenarios are viewed as an alternative image of the future based on projected future socio-economic, demographic and technological change
A1 Family
more integrated world of rapid economic growth with a global population that reaches 9 billion in 2050
world with new and more efficient technologies
extensive social and cultural interaction world wide and a convergence in terms of income and way of life between nations
A2 Family
a more divided world with high population growth, slow economic growth and technological development.
independently operating nations with regionally oriented economic development
B2 Family
a world more divided but more ecologically friendly like B1 family with slower population growth than the A2 family
emphasis on local solution to economic, social and environmental stability with less rapid and more fragmented technological change than the A1 and B1 families
B1 Family
integrated world with population growth as A1 family, but with more rapid changes in economic structure towards a service and information economy
future reduction in material intensity and introduction of clean resource and efficient technologies with emphasis on global solutions to economic, social and environmental stability
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19. Applying Climate Change to the WBM
Downscaled temperature was used to estimate future evaporation
Downscaled rainfall and temperature was used as input into the NAM hydrological model to estimate future runoff into the lake
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20. Results of Projected Rainfall over the lake
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21. Results of Projected Evaporation over the lake
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22. Applying Climate Change to WBM
The estimated changes in rainfall, runoff and evaporation derived from HadCM3 for the period in 25 years mean scenarios were applied to the Lake Malawi WBM.
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23. Pattern of the future behavior of the lake
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24. Summary and Conclusion
Under both emission scenarios the water level continues to drop from 2001 up to 2100.
Mean monthly lake levels shows that during the first quarter of the century the water level ranges from to m amsl with a drop at the end of the first quarter then starts to gain till the mid of the second quarter of the century. From the mid of the second quarter of the century the water level ranges from to and till mid of the third quarter of the century.
A marked drop was observed in the last quarter of the century where the water level range ranges from to
The lowest lake level has been predicted at mid of the last quarter of the century by both emission scenarios.
A total fall in water level of the order 0.5 to 1.0 m is forecast for this century based on climate change.
Question B8: On average, how many hours per week did you spend on study activities outside of courses/classes (e.g. library time, group discussions) during the course of your study?
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25. Summary and Conclusion
The results further shows that it is very unlikely for the water level to increase to a maximum height of 477 m amsl as was in 1980
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Recommendation
There is agent need to reduce pressure on the water resources development along the Shire river by a balanced water resources development set up to be spread throughout the country to avoid overdependence on the Shire river as it is the case now.
For the ultimate performance of the model it is recommended that the model should be updated on regular basis based on the current observed data due to uncertainties in GCM emission scenarios in predicting future climate.
The GCM used in the study should serve as an example of one possible future climate pattern of the lake
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Acknowledgement
Many thanks to
Prof Alan Ervine (Late) University of Glasgow
Mr Amon Chirwa (Late) Ministry of Irrigation and Water Development
United Kingdom (UK) Meteorological Office Hadley Centre
University of Glasgow, Water Research Lab Team
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THANK YOU
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