Water from various origins is used to supply irrigation: Surface water from close resource or transported on long distance, groundwater from shallow water tables or from deep aquifers as well. Multiple resources may be available at the same place, differing in operation cost, in quantity and in quality. Other usages may compete with irrigation. Therefore, an assessment of the total amount of water available during an irrigation season is essential for determining the optimal consumptive as well as non-consumptive use, the latter remaining available for a second usage. Dependent on the local conditions, groundwater irrigation may be more efficient than surface water schemes. Both may be used together on the same spot. However, especially in arid and semi-arid conditions, there is often a need to stop over-exploitation and ensure sustainable use by technological and institutional interventions so that, where possible, storages could be used during the drought periods.

Sustainable water management at both resource and system level is not only an important requirement in support of global food production, but also for the livelihood of the rural population and for environment. In addition there is the important aspect of integrated river basin management where irrigation is generally the major water user. In quite numerous systems there is 'over' irrigation, which may result in waterlogging, salinization and wasting of water. On the other hand 'deficit' irrigation may result in yield reductions and salinization of the root zone. Therefore a crucial question is what would be optimal water development strategy and management approach in irrigation under the local conditions. The WG will be exploring the subjects under its scope from perspective of”schemes” and thus is relevant to the Thematic Area.

Scoping Document