Controlled drainage for improved water management in arid regions irrigated agriculture

In arid regions, controlled drainage is the next logical step towards improving water management in irrigated agriculture and reducing the environmental impacts of subsurface drainage flow. Controlled drainage has been practiced in humid areas for a long time. In this paper traditional subsurface drainage system design procedures are described, followed by alternative design criteria for arid regions and suggestions for system design to include control structures that enable better drain system management. The suggested changes include reducing the installation depth of laterals, accounting for crop water use from shallow ground water in the design, and relaxing the mid-point water depth requirement. Active control of drainage systems in arid irrigated regions is a developing concept that is currently being evaluated around the world. Research in the U.S. and Australia has demonstrated that water tables in irrigated areas can be effectively controlled with various types of structures. Control has resulted in reduced volumes of drainage water and total salt loads discharged. Salt accumulation in the root zone is a consideration in adopting controlled drainage, but other research has demonstrated that it is possible to manage salt accumulation through careful water management.