Irrigation Demand in Humid Areas [and Discussion]

Irrigation demand in humid regions is at present primarily determined by population growth and the consequent food demand. Most of the population is in Asia, and most of the food demand is for rice. Rice production has increased in recent years at rates considerably ahead of projections. Advances in research on rain-fed rice suggest that the high demand of rice for water may be reduced, and yields in rain-fed areas increased significantly. Thus projections of irrigation demand in humid areas may be greater than necessary. Higher yields have led to lower rice prices in real terms, so that investment in new irrigation systems, including shallow tube-well systems, may be uneconomic if rice is to be the principal crop produced. Rehabilitation and improved management of existing systems can lead to more efficient water use, and a much better investment of resources. As the rice demand is satisfied, irrigation will increasingly be used for other crops. In Africa and Latin America only limited irrigation development has taken place in humid regions, although substantial opportunities exist.