Book excerpt: In many countries irrigated agriculture consumes a large proportion of the available water resources, often over 70% of the total. There is considerable pressure to release water for other uses and, as a sector, irrigated agriculture will have to increase the efficiency and productivity of its water use. This is particularly true for manually operated irrigation systems managed by government agencies, which provide water for a large number of users on small landholdings and represent 60% of the total irrigated area worldwide. --