The multiple personalities of water conservation

“Water conservation” means different things to different people and the principles of depletion and diversion are often confounded and misconstrued, particularly when the different perceptions of the value of water and units of analysis are involved. Many public policies and public and private investments have been implemented in the name of conserving water, particularly in irrigated agriculture. Unfortunately, many of these policies and investments cannot make additional water available to new users owing to the nature of closed basin hydrology. The assumption that farmers are low-efficiency irrigators is used to justify transfer of income and wealth to agricultural water users and others through direct investments and cost sharing programs. Instead, these programs serve to sustain and increase consumptive use of water in agriculture and disrupt the existing hydrologic balance. In arid climates, where deficit irrigation is practiced, conventional water conservation measures such as drip irrigation often result in increased depletion at the individual farm level and less water available for other users. This paper discusses water conservation misconceptions, particularly those related to irrigated agriculture in the arid southwestern United States. Deficit irrigation is a common practice throughout the southwest, the region is experiencing rapid population growth and naturally limited water supplies have been exacerbated by current drought conditions. In this paper, the water conservation impacts of drip irrigation, irrigation scheduling and canal lining are discussed in the context of the hydrological assumptions that are used to promote these technologies. The potential of drip irrigation, irrigation scheduling and canal lining to sustain and increase crop evapotranspiration in deficit irrigation environments is illustrated. Given hydrologic conditions, the authors conclude that accurate basin-wide accounting of water use, including equitable distribution based on existing legal entitlements would significantly contribute to water conservation efforts.