|Ayars, James - Jim|
Submitted to: CAB International United Kingdom
Publication Type: Review Article
Publication Acceptance Date: 3/14/2007
Publication Date: 7/3/2007
Citation: Ayars, J.E., Christen, E., Hornbuckle, J. 2007. Managing Irrigation And Drainage In Saline Environments. CAB Reviews: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resourcs 2007 2, No. 040. Interpretive Summary: Environmentally responsible disposal of saline drainage water is critical to sustain irrigated agriculture in arid and semi-arid lands. As environmental regulations become more restrictive, it has become increasingly more difficult to discharge drainage water in surface water systems. One alternative is to discharge into evaporation ponds as the ultimate disposal point. This is possible in Australia but not in California due to the presence of toxic trace elements in the drainage water in California but not Australia. Another alternative that has been researched in both California and Australia is biological concentration of salt through successive reuse of drainage water for irrigation. In the process the volume of drainage water is reduced and the concentration of salt is increased due to the loss of water. This process is described along with the theoretical and practical basis for the operation of this type of system. In California the system is called Integrated on-Farm Drainage Management (IFDM) and in Australia it is called serial biological concentration (SBC). Successful operation of these systems will result in zero discharge of saline drainage water into the environment. These systems are economically feasible only if the highest levels of irrigation management are practiced. This minimizes the throughput of drainage water and the area required for disposal. It also maximizes the area that can to be allocated to growing the most profitable crops.
Technical 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 surface streams, lakes, and rivers with significant negative environmental impacts a practice that can no longer continue. As water supplies to agriculture become limited there will be increased use of degraded water 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 saline drainage water into either an evaporation pond or a spray evaporation facility. Bio-concentration facilities were developed in California, USA and Australia and are called integrated on farm drainage management (IFDM) in California or serial biological concentration (SBC) in Australia and there is a limited history of operation. 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. Irrigation management has to be improved to the highest practical levels. New salt management concepts have to be evaluated or implemented to include using halophytes and accepting higher levels of salinity in the soil profile. Drainage water management is implemented to include managing water table position and implementing new design and construction of subsurface drainage systems. Additional facilities are required to provide disposal capability in either an evaporation pond or a spray facility. We review the concepts associated with the design and operation of bio-concentration systems highlighting the requirements for success and the limitations of these particular facilities.