Your search found 6 records
1 Ong, C. K.; Odongo, J. C. W.; Marshall, F.; Black, C. R. 1991. Water use by trees and crops: Five hypotheses. Agroforestry Today, 3(2):7-10.
(Location: IWMI-HQ Call no: P 1992 Record No: H08694)
2 Ong, C. K.; Khan, A. A. H. 1993. The direct measurement of water uptake by individual tree roots. Agroforestry Today, 5(4):2-5.
(Location: IWMI-HQ Call no: P 3374 Record No: H014190)
3 Ong, C. K.; Wilson, J.; Deans, J. D.; Mulayta, J.; Raussen, T.; Wajja-Musukwe, N. 2002. Tree-crop interactions: Manipulation of water use and root function. Agricultural Water Management, 53(1-3):171-186.
(Location: IWMI-HQ Call no: PER Record No: H029533)
4 Ong, C. K.; Swallow, B. M. 2003. Water productivity in forestry and agroforestry. In Kijne, J. W.; Barker, R.; Molden. D. (Eds.). Water productivity in agriculture: limits and opportunities for improvement. Wallingford, UK: CABI; Colombo, Sri Lanka: International Water Management Institute (IWMI) pp.217-228. (Comprehensive Assessment of Water Management in Agriculture Series 1)
(Location: IWMI-HQ Call no: IWMI 631.7.2 G000 KIJ Record No: H032644)
5 Mungai, D. N.; Ong, C. K.; Kiteme, B.; Elkaduwa, W.; Sakthivadivel, Ramaswamy. 2004. Lessons from two long-term hydrological studies in Kenya and Sri Lanka. Agriculture, Ecosystems and Environment, 104:135-143.
(Location: IWMI-HQ Call no: IWMI 551.48 G744 MUN, PER Record No: H037478)
6 Ong, C. K.; Black, C. R.; Muthuri, C. W. 2006. Modifying forestry and agroforestry to increase water productivity in the semi-arid tropics. CAB Reviews: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resources, 1(065). 19p.
Water productivity ; Forestry ; Agroforestry ; Arid zones ; Water demand ; Water use ; Water use efficiency ; Stream flow ; Eucalyptus
(Location: IWMI HQ Call no: e-copy only Record No: H043682)
(0.38 MB)
The need to increase water productivity is a growing global concern as the World Commission on Water has estimated that demand for water will increase by c.50% over the next 30 years and approximately half of the world’s population will experience conditions of severe water stress by 2025. Three-quarters of African countries are expected to experience unstable water supplies, where by small decreases in rain fall induce much larger reductions in stream flow Vital water catchments have been lost or are being degraded, creating concerns about the loss of hydrological functions and increasing competition for scarce water resources between agriculture, urban centers, industry and wildlife. The challenge is to improve water productivity at the landscape or river basin level, especially for the rapidly growing populations in many developing countries. Water productivity is define as the value or benefit derived from the use of water. In this review, we describe recent finding regarding the hydrology of forests and agro forestry systems and indicate how modification to tree-based systems may increase water productivity in the semi arid tropics. Throughout the tropics, reforestation using eucalyptus has been the most significant approach for modifying the water productivity of forestry and agro forestry systems. Fortunately, the ‘eucalyptus dilemma’ of providing local benefit at the expense of decreased stream flow for downstream users has been well articulated in many countries where evidence-based research has changed water policy and discouraged further planting of eucalyptus on water catchments. In East Africa, the most popular replacement for eucalyptus has been another exotic from Australia, Grevillea robusta, which has become the species of choice for farmers in the sub-humid highlands. However, attempts to introduce this species to semi-arid areas have been disappointing due to its evergreen canopy and consequently high demand for water. Current attempts to use deciduous species such as Melia volkensii and Paulownia fortune in such areas are much more encouraging, although the long-term implications are still unknown. Agro forestry has the potential to improve water productivity in two ways. Trees can increase the quantity of water used on-farm for tree or crop transpiration and may also improve the productivity of the water that issued by increasing the biomass of trees or crops produced per unit of water used. Plot-level evidence shows that improvements in water productivity resulting from modification to the microclimate experienced by crops may be limited. Instead, evidence from semi-arid areas of India and Kenya has shown that the greater productivity of agro forestry systems is primarily due to the greater quantity of water used. Further research is needed to examine the impact of the increased water use on drainage and base float the landscape level. Finally, we describe some of the technical approaches, which may be used to improve water productivity based on differences in tree phenology and the challenges facing small holders in areas of growing water scarcity.
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