1. Water and Agroforestry
Chin Ong, 29 June 2007
ICRISAT Center, Patancheru, India, 1985

2. ICRAF’s research on water,1991-2007
• Past, present and future issues
• Machakos (‘Mecca’ for land recovery & agroforestry)
• Challenges of more trees & climate change
1986 2000
Upper Mbeere
Thika
Thika
Machakos
Source: Anyango, 2005

3. More people, less erosion
Tiffin & Gichuki,1997
Machakos, 1991
Machakos, 2006

4. More people, more trees
Embu, 1997

5. Majjia Valley,Niger, 1975-2002
More rain or more soil conservation? Source: C. Reij

6. Impacts of land recovery in Niger &
Machakos
• More adoption of water
harvesting
• Increase in dry season
cultivation
• Higher incomes
• Improved nutrition
• More firewood
• More fodder
• Less time fetching water Quickbird image of Lare, Nakuru District, 2006
Malesu et al. 2006

7. Machakos, 1991-2000
Hypothesis: Trees can capture and use resources more efficiently than crops

8. Machakos Research, 1985-1992
1991 1991
Strong focus on alley cropping and erosion
However, large plots indicate little or no improvement in
crop yields.
Controls plots invaded by tree roots.
(Ayeampong et al. 1995)

9. Microclimate improvements
1993 1995
Hypothesis: Improvements in microclimate lower soil evaporation & promote
hydraulic lift.
Maturity delayed by 2 weeks due to lower temp (-4C). Soil water benefit is not as
important.
Climate change benefits?
Ong et al. 2000. Agric. Ecosyst. Environ. 80: 121-145

10. Shade benefit on coffee?
Which tree species?

11. Shade benefit on tea?
Which tree species?

12. Complementarity in water uptake
1992 1995
Focus attention on Grevillea robusta-maize in different arrangements
Hypothesis: Deep roots of grevillea is highly compatible with maize.
Howard et al. 1997. Agrofor Sys. 35: 15-29

13. Fast-growing trees & competition
1997 1997
RAC: Root studies of fast-growing trees
Is the answer below-ground?
Ong et al, 2002. Agr. Water Manag. 53: 171-186

14. Fractal index & root studies
1994 1996
Fractal index = ratio of lateral vs vertical roots
Index determined for a range of species. How useful?
Ong et al.1999. Agrofor.Syst.44: 87-103

15. Water balance
1996 1996
Total transpiration by sole maize was only 50% rainfall
85% by agroforestry systems, including 25 % during the dry season
Lott et al . 2003. For. Ecol. Mange 180: 45-59

16. Long-term consequences of different resource
capture strategies?
July 2006
Melia volkensii, 13 yr
Cautious spender: deciduous & lateral rooting
Machakos, July 2006
Grevillea, 15 yr
Big spender: evergreen & deep rooting

17. Comparison of deciduous & evergreen trees
Melia volkensii, Machakos, 1997 Paulownia fortunei, Naro Moro, 2001

18. Land use change & stream flow
Loss of watershed function
of the Mau Complex
Evidence?
Sondu-Miriu hydropower plant

19. Mau Forest Change 1973 - 2005
Key areas of
deforestation include:
 Eastern Mau
 Western Mau
 Masai Mau
Lowery, 2005

20. Stream flow of Nyando River
Nyando, 1968-1991
1600
Cumulative streamflow (mm)
1400
1200
1000
800
600
400
200
0
0 5000 10000 15000 20000 25000 30000 35000 40000
Cumulative rainfall (mm)
Long term river flow is 4% of annual rainfall ( Sang, 2007)

21. More erosive rain is predicted for Lake Victoria Basin!
Katuk Odeyo, 1998 Quickbird, Katuk Odeyo, 2004
Source : Meshak

22. Green-blue water globally
Source: SEI

23. Green and blue water fluxes in Kenya
Source: SEI

24. Eucalyptus: an ecological time-bomb?
• Millions of eucalyptus were planted in
Mau & Central Kenya.
• What will be the ecological impacts?
• Promoted by Forest Department & for
Carbon Trade by TIST.
• 250m3 of water for one ton of carbon!
grevillea
1 year old eucalyptus uses 30 litres of water per
day! Juja 2007
Sap flow equipment for water uptake

25. Map of Eucalyptus Impact on Streamflow in South Africa
Source: Mark Gush,2005

26. More trees with less water?
Naro Moro: Muthuri et al. 2004

27. Lessons & challenges for ICRAF
• Predicted changes in land use & climate will
have serious impacts on water supply &
erosion
• Strong tradeoffs with carbon credits: which
profitable trees to plant without loss of
ecosystem services?
• Machakos lessons: long-term evidence is
needed, reserve water for ecosystem De Wit 2006
functions.
• Make science more meaningful to policy
makers e.g. eucalyptus, bioenergy & water
• Connecting upstream & downstream,
combining land management across scales
e.g. Green blue water initiative with
Stockholm Environment Institute on Lake
Victoria Basin
• Where are the future Machakos?

28. Acknowledgements
Contributions & dedication of countless
students & technicians.
Partners: Nottingham, Bangor, Dundee,
JKUAT, IH, UWA, Sokoine, Cornell, Florida
Donors: DFID, Sida, ACU, DAAD, BMZ
ICRAF: Peter Huxley, Tony Young
Meka Rao, Ahmed Khan
RELMA team

29. The future is bamboo
Economy class Club class
For zero carbon footprints!