Submitted to: ASABE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: 4/10/2009
Publication Date: 6/21/2009
Citation: Ayars, J.E. 2009. Sustaining Irrigated Agriculture in Arid Areas: Lessons Learned in the San Joaquin Valley. ASABE Annual International Meeting. 095522. Interpretive Summary: Irrigated agriculture has a significant role to play in feeding the world population. It currently provides 35% of the food produced on only 17% of the world’s arable land. However, there are negative environmental impacts associated with irrigation that need to be considered and managed. The major impacts are the salination of land and the discharge of drainage water containing salt and possibly other toxics which can harm the environment. Over the past 19 years farmers in the San Joaquin Valley have been developing methods to minimize the environmental impact while maintaining productivity. Results from field research has demonstrated that reducing the field length in surface irrigation, reducing pre-plant irrigation times, and use of sprinklers for pre-plant irrigation and the first seasonal irrigation have significantly reduced the drainage water volume. Use of sprinkler and drip irrigation has also resulted in significant reduction in deep percolation and drainage water. A sequential biological evaporation system that reuses drainage water for irrigation and thus reduces the drainage volume in combination with improved irrigation management has been shown to be an effective disposal methodology. These are all techniques that are easily implemented and are applicable for use throughout the world.
Technical Abstract: The conventional wisdom is that drainage is required to sustain irrigation in arid and semiarid areas. However, disposal of saline drainage water is a problem throughout the world that is challenging the sustainability of irrigated agriculture. The presence of elements besides salt in the drainage water may create environmental hazards. Selenium in the drainage water in the San Joaquin Valley resulted in the closure of drains and the elimination of saline drainage water disposal on approximately 400,000 ha of land of on the West side of the Valley. The use of pressurized irrigation systems, drip and center pivot, has significantly reduced deep percolation losses. Reusing saline drainage water for irrigation has also been implemented and contributes to the reduction in drainage volume. Using subsurface drip irrigation in areas with shallow ground water has been shown to be sustainable and not require drainage. On farm disposal of saline drainage water has also been developed as an interim solution. The combination of improved irrigation system design and management has significantly reduced the volume of drainage water needing disposal. This paper discusses these technologies and the effects on drainage water disposal and the required level of drainage needed to sustain irrigated agriculture.