Sustaining Irrigated Agriculture in Arid Areas:Lessons Learned in the San Joaquin Valley

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.