DESIGN OF AGRICULTURAL DRAINAGE WITH ADAPTIVE IRRIGATION MANAGEMENT

This paper describes a new approach to designing field-scale irrigation and drainage systems in arid irrigated areas. This approach allows for a drainage design that can adjust to irrigation schedules to alleviate waterlogging and salinity problems. This approach has been implemented in a computer model. The computer model contains a feedback loop between the irrigation scheduling and the drainage design components. The modular components of the system are a weather generator, irrigation scheduling, upward flow, salinity of the irrigation water, transient-state drainage design, and crop production. The model modifies the irrigation schedule taking into consideration the effects on the drainage design. The performance of the system is evaluated using the net benefits, as well as explicitly addressing the stochastic nature of irrigation and drainage. The model is constructed so the irrigation and drainage components may be varied individually to study the impact on the whole system. This capability will allow the user to quantify the cost of minimizing drainage water production by modifying the irrigation schedule.