At first glance, it appears that the region is well endowed with water resources. While accounting for only about 16 percent of the world's land surface, it receives 22 percent of its precipitation and produces 28 percent of its renewable water resources. However, the region is home to 53 percent of the world's population and its IRWR [internal renewable water resources] are only about half of the world's average. By and large, most countries in Asia (except for Singapore, Maldives and Republic of Korea) are still not considered water-stressed. However, even in countries with high level of per capita water availability, large segments of the population are beset with water scarcity as a result of the large variations in the spatial and temporal distributions of rainfall and stream flow. About 84 percent of the total water withdrawal of the region is for agriculture. Irrigation accounts for the bulk of water use in agriculture due to the large irrigation base and the fact that approximately half of the irrigated area is devoted to flooded rice production. Although still relatively small in most Asian countries, the industrial, municipal and environmental demands for water continue to increase at a rate twice that of population growth. The proportion of water available for agriculture is projected to decline to 62 percent worldwide and 73 percent in developing countries by 2020. Hence, the opportunities for expanding the irrigation base are limited. If food security is to be maintained, ways of increasing water productivity must be found. A host of interrelated issues must be addressed in the short-and-medium terms if a water crisis in the region is to be averted. Among others, these include: changing demand patterns, impact of climate change and watershed modifications on dependable water supply, low water productivity in agriculture,in adequate investments in water supply systems to meet future demands, a shift toward decentralized and privatized water service and market mechanisms, the need to reduce non-revenue water, sustaining and expanding the irrigation base, recycling wastewater for agriculture, access to water of the rural and urban poor, groundwater mining, the need to strengthen international collaboration for managing shared water resources, protection of freshwater ecosystems, and fostering a favorable environment for a comprehensive water resources policy and program frameworks. The specific issues in irrigation that are more pressing were discussed. Suggestions on how to address these issues were presented. Two very significant changes in irrigation development policy and strategy in many developing countries of Asia were discussed. First is the shift from large, gravity irrigation systems towards small privatized farmer-controlled irrigation systems such as shallow tubewells, low-lift pumps, farm reservoirs and diversion dams. Second is the dramatic shift from the virtual monopoly of the central role of national government towards greater participation of other players such as WUAs [water users association], NGOs [non governmental organizations], and local government units. The public sector activities are now focused on improving the management of water at the main system level and adopting new policies aimed at creating incentives for WUAs or cooperatives to take over the O and M [operation and management] of the rest of the irrigation facilities.

Cet article fait le point sur l'etat actuel des connaissances en matiere de consommations d'eau pour l'irrigation en France, tres variables dans le temps et l'espace. Au cours des dix dernieres annees, les superficies irriguees ont augmente de facon importante mais variable selon les regions, malgre la reforme de la PAC. Avec 43 % de la surface irriguee, le mais reste la principale culture irriguee. La connaissance des superficies irriguees, satisfaisante sur le plan statistique, est insuffisante pour une estimation quantitative des prelevements d'eau pour l'irrigation, du fait de la variabilite importante des besoins en eau des cultures et de la meconnaissance des pratiques d'apports d'eau des irriguants. Le Cemagref [Institut de recherche pour l'ingenierie de l'agriculture et de l'environnement] a developpe une methode d'estimation a l'echelle regionale des apports d'eau d'irrigation lors d'une secheresse severe. Les besoins en eau theoriques du mais, choisi comme culture de reference, sont evalues pour les principales regions de production, a partir des donnees climatiques et des caracteristiques des sols et en tenant compte des pratiques de restriction des apports d'eau des irriguants lors d'une secheresse prolongee. Sur la base de ce travail, il est possible de proposer un dispositif de suivi et d'analyse previsionnelle de la demande en eau des agriculteurs a l'echelle regionale, de facon a mieux apprecier les risques de tensions sur la ressource, et a mettre en place des modes de gestion plus efficaces. Ce dispositif devra s'appuyer entre autres sur une meilleure connaissance des pratiques des irriguants