Irrigation scheduling under saline high water tables [Economic crops, San Joaquin Valley, California]

Approximately 400,000 acres in the San Joaquin Valley are classified as drainage problem areas. Levels of soil salinity detrimental to crop yield exist in these areas because of saline high water tables. One water district serving 264,000 acres needing drainage estimated that their production loss caused by drainage problems was about $17 million in 1981. The traditional way of solving these problems is to install a subsurface drainage system, which removes the excess subsurface water to some disposal facility. Unfortunately, no completely satisfactory method of disposal exists in the San Joaquin Valley. Current disposal methods include discharging drainage water into surface water channels and evaporation ponds. Recommended future plans call for construction of a valley-wide master drain to convey drainage water out of the valley. Regardless of the disposal method, growers in problem areas need to reduce the volume of drainage water discharged by means of proper design and management of their irrigation systems. One aspect of management is scheduling of irrigations.