Drainage water reuse: biological, physical, and technological considerations for system management

Previous reviews of drainage water reuse have discussed principles of water reuse and disposal; provided examples of reuse practices; offered reuse criteria for salinity, for trace elements, and for bacteria; discussed mitigation of dissolved trace elements in reuse strategies; and summarized the California experience with a focus on discussion of salinity, sodicity, B, Mo, and Se issues. This review emphasizes recent literature contributing to understanding physical and biological constraints to drainage water reuse. The potential for drip irrigation and, particularly, low-flow/high-frequency systems to enhance the use of drainage water while minimizing the deleterious effects on yield and on water and soil resources is examined using the numeric HYRDUS-2d model. Additionally, an analytical model is used to illustrate physical and biological limitations to drainage water management that result from the self-regulating nature of the soil-plant-water system. The models suggest that crop, soil, irrigation frequency, and delivery systems might be manipulated to reduce the quantity of drainage water, but they also suggest that the nature of the system may seriously constrain the amount of reduction that might be achieved.