Managing irrigation and drainage in saline environments

Abstract

Disposal of saline drainage water is one of the most vexing problems facing irrigated agriculture. The sustainability of irrigation will require that cost-effective and environmentally acceptable methods be found for disposal of saline drainage water. Oftentimes, drainage water contains fertilizers, pesticides and toxic trace elements in addition to salt. Currently, disposal is accomplished by discharging drainage water into streams, lakes and rivers with significant negative environmental impacts; this is a practice that can no longer continue. As water supplies to agriculture become limited there will be increased use of degraded water for irrigation, which adds additional contaminants to the drainage water. There is a need to develop an alternative drainage water disposal strategy. One alternative disposal strategy is the concept of biological concentration of salt and ultimately disposal of a small volume of drainage water into either an evaporation pond or a spray evaporation facility. Bioconcentration facilities developed in California and Australia are called Integrated On-Farm Drainage Management (IFDM) in California or Serial Biological Concentration (SBC) in Australia, respectively. These systems represent the integration of the accumulated knowledge related to irrigation management, salt management, reusing saline drainage water, and drainage water management. The successful operation of these facilities requires an integrated approach to irrigation and drainage system design and management with irrigation management improved to the highest practical levels. New salt management concepts need to be evaluated or implemented to include using halophytes in production systems and accepting higher levels of salinity in the soil profile in general agronomic production. Drainage water management is implemented to include managing water table position and implementing new design and construction techniques for subsurface drainage systems. Additional facilities are required to provide disposal capability either as an evaporation pond or a spray evaporation facility. We review the concepts associated with the design and operation of bioconcentration systems highlighting the requirements for success and the limitations of these particular facilities. © CABI Publishing 2007.