Fortunately, there is ample scope to improve water pro­ductivity and basin efficiency, to minimize additional water needs (Molden et al., 2007). AKST plays an important role in achieving these improvements. Three broad avenues to increase agricultural production while minimizing water use are to (CA, 2007) (1) improve productivity in rainfed settings, (2) increase productivity in irrigated areas, and (3) expand international agricultural trade. The scope and relevant pol­icy measures differ considerably by region (Table 5-20).
5.4.5.1 SSA
Considering the ample physical potential and the willing­ness of donors to invest in African agriculture, the scope of irrigated area expansion is large. But the contribution of irrigation to food supply will likely remain limited (less than 11% of total food production), even after doubling its area. The investment cost of doubling the irrigated area is high and to make this investment economically viable massive investments in marketing infrastructure are needed

(roads, storage, communication) (Rosegrant et al., 2005). On the other hand, investments in irrigated area expansion for high-value crops (vegetables, cotton, fruits) can be an important vehicle for rural growth, and poverty alleviation particularly when geared to smallholders. Without substan­tial improvements in the productivity of rainfed agriculture, food production in SSA will fall short of demand. From a biophysical point of view, water harvesting techniques have proven successful in boosting yields, often up to a two or threefold increase (Röckstrom, 2003, 2007). But, low adop­tion rates of water harvesting techniques indicate that up-scaling local successes pose major challenges for AKST.

5.4.5.2 South Asia
In South-Asia 95% of the areas suitable for agriculture are in use, of which more than half are irrigated. The biggest scope for improvement lies in the irrigated sector where yields are low compared to the obtainable level. Under a high productivity variant, all additional water and land for