ABSTRACT
Abstract Colorado River water is the only available source of irrigation and drinking water in the Imperial Valley. As much as 345,375 ha-m (2.8 million ac-ft) of Colorado River water are used every year to irrigate more than 202,342 ha (500,000 acres) of land in the Imperial Valley. The recently proposed water transfer draft between Imperial Irrigation District and the San Diego County Water Authority calls for transfer of up to 49,337 ha-m (400,000 ac-ft) annually of Imperial Valley's allotment of Colorado River water. This study was conducted to evaluate the potential availability of water for transfer and the economic value of conserved water from two on-farm water conservation measures; 1) implementation of tailwater return systems and 2) implementation of pressurized irrigation systems. Implementation of tailwater return systems is limited to field crops grown on heavy clay soils and implementation of low-volume irrigation systems is only feasible on specific vegetable crops. The implementation of tailwater return systems will reduce surface runoff from the current Valley-wide average of 16.8% (of delivered water) to approximately 5% and may yield a maximum potential savings of approximately 24,454 ha-m (198,253 ac-ft) of water. The implementation of low-volume pressurized irrigation systems may yield a maximum potentials savings of approximately 12,237 ha-m (99,209 ac-ft) of water. The use of low-volume irrigation systems requires high capital investment and significant changes in cultural practices. It also yields higher value of conserved water as compared to tailwater recovery systems. Costs associated with decline in yield and increase in soil salinity should be considered in determining the economic value of water. Keyword: Irrigation management, water availability, water conservation, water transfer.
