Economic and agronomic strategies to achieve sustainable irrigation

The achievement of sustainable irrigation in arid regions requires greater attention to waterlogging, salinization, and degradation of ground and surface waters, which are among the problems that continue to threaten productivity and degrade environmental quality. We consider sustainability to be achieved when irrigation and drainage are conducted on-farm, and within irrigation districts, in a manner that does not degrade the quality of land, water, and other natural resources, either on-farm or throughout an irrigated region. Sustainability may also be described as maintaining the productive resources required for irrigation, so that future generations may have the same opportunity to use those resources as we do. Given the increasing importance of irrigated land for food production, the time has come when it is vital to intercept, reuse, and isolate drainage waters within the regions in which they are generated. Adoption of this strategy can be enhanced by policies that require farmers, and irrigation districts, to consider the off-farm impacts of irrigation and drainage. Such policies include linking water rights with salt rights to require the monitoring and management of both irrigation water and the salt loads in drainage waters. We review the knowledge gained since the early 1970s regarding the economic and agronomic aspects of irrigation and drainage, with a focus on drainage water reduction and sequential reuse of drainage water on salt-tolerant crops. Economic incentives that motivate farm-level and district-level improvements in water management are also reviewed. We conclude that adequate knowledge exists for implementing strategies that focus on water use and salt disposal within irrigated regions, and we recommend policies that will motivate improvements in productivity and enhance the likelihood of achieving sustainability.