1. Analysis of Hydro-climatology of Malawi
Cosmo Ngongondo
2017 World Water Day, 20 March 2017, Mangochi, Malawi
Department of Geography and Earth Sciences,
Faculty of Science, University of Malawi,
Chancellor College, P.O. Box 280, Zomba, Malawi

2. Background
Water resources availability at any temporal and spatial scales is governed by complex interactions between climate and hydrological processes
Need: Analyse observed hydroclimatic parameters to inform future water availability
Data Scarcity: A challenge in many parts of the developing world
Need less data intensive approaches

3. 20th Century runoff trends
Fig. 1: Observation driven global runoff trends
Piao et al 2007, PNAS 25 , doi/10.107/pnas

4. 20th century river discharge trends
Fig. 2: Observed river discharge trends during
Large catchments > 50,000 km2
Based on difference between relative to
10-40% decreases in observed river discharge over southern Africa
Milly et al 2005, Nature, 438, doi: /nature04312

5. Key Water Challenges in Southern Africa
Rapid population and economic growth
Expansion of irrigated agriculture
Transboundary water transfers (Botswana and Namibia
Ecological Needs
Climate Change – potential for international water conflicts
Beck & Bernauer (2011)

6. Study Aims Analyse the hydro-climatology of Malawi from 1971 to 2001
Model the water balance components (Rainfall,
Temperature, Potential & Actual Evapotranspiration,
Runoff
Analyse their temporal trends
Based on Ngongondo et al. (2015), Quart. International & Ngongondo et al. (2011), Theor. & Appd Climatology
Compare the temporal patterns with Lake level and river flow response

7. Data and Methods Thornthwaite Monthly water balance model Model Inputs
Monthly Rainfall
Monthly Temperature
Soil moisture capacity
Latitude
Outputs
Potential ET
Actual ET
Runoff
Time slice:
Fig. 3

8. Data Analysis Areal mean of standardised anomalies series
Mann-Kendal statistic: trend direction and significance (a=0.05) (WMO Recommended)
Slope: Linear Regression
Station Water Balance values were Interpolated on Map of Malawi using ordinary Krigging

9. Climate Stations
28 Synoptic stations
Fig. 4

10. Climate Stations
Fig. 5

11. Summary of Malawi Hydro-Climate

12. Standardised anomalies series (1971-2001)
Rainfall
Temperature
Runoff
PET
AET
Contrasting patterns of PET and AET
Fig. 5

13. Trends in monthly water balance
Rainfall
Temperature
PET
AET
Runoff
Fig. 6

14. Complimentary ET relationship
ETp+ ETa= 2ETw
Water limited environments
Energy limited environments

15. Complimentary ET relationship
ETw
Radiative budget: increase results in both Eta and Etp increase
Advective budget: increase results in decreased Eta and increased Etp
Increase in water limitation as a result of the reduced rainfall

16. Lake Malawi Monthly Levels (1898-2017)
1899 to 1979/80
Minimum=Dec 1915 ( m)
Maximum= May 1980 (477.2 m)
Mean= m

17. Lake Malawi Annual Levels (1898-2017)
Mean= m
Maximum= 1979/80 (476.5 m)
Minimum= 1914/14 (470.4 m)
Significant positive MK trend, slope m per year

18. Lake Malawi Monthly Levels (1898-1979)
Minimum= Dec 1915 (469.9 m)
Maximum= May 1979 (477.1 m)
Mean= m
Significant Positive MK Trend with
slope= m per month

19. Lake Malawi Monthly Levels (1899-1979)
Minimum= 1914/15 (473 m)
Maximum= 1979/80 (476.4 m)
Mean= m
Significant Positive trend with
slope m per year

20. Lake Malawi Monthly Levels (1979-Feb 2017)
Minimum= Dec 1995 (473 m)
Maximum= May 1980 (477.2 m)
Mean= m
Significant Negative
MK Trend ,
slope=-0.04 m per month

21. Lake Malawi Monthly Levels (1979-2016)
Mean= m
Maximum=476.5 m
Minimum=473.4 m
Significant Negative
MK trend, m per year

22. Monthly lake Levels periodicity

23. Monthly lake Levels periodicity (Detrended Series)

24. Ruo River @ M1 Road Bridge
Catchment area: 193 km2
Significant negative MK trend

25. Linthipe @ Kamuzu Bridge
Significant negative MK trend

26. Summary Malawi’s Climate and hydrological cycle are intimately linked.
Most projections show large parts of southern Africa are getting warmer- signficant temperature increase in Malawi
Rainfall decreasing (not Significant)
AET and Runoff following rainfall pattern- Moisture limitations
Lake Malawi levels and some key river flows decreasing- Climate signal+ catchment processes+ noise

27. Thank you !