OPTIMAL STOCHASTIC MULTICROP SEASONAL AND INTRASEASONAL IRRIGATION CONTROL

Optimal seasonal multicrop irrigation water allocation and optimal sto chastic intraseasonal (daily) irrigation scheduling are carried out us ing a two-stage decomposition approach based on a stochastic dynamic p rogramming methodology. In the first stage the optimal seasonal water and acreage allocation among several crops or fields is defined using deterministic dynamic programming with the objective of maximizing tot al benefits from all the crops. The optimization is based on seasonal crop production functions. Seasonal crop production functions are obta ined using single-crop stochastic dynamic programming, which incorpora tes the physics of soil moisture depletion and the stochastic properti es of precipitation. In the second stage optimal intraseasonal irrigat ion scheduling is performed using a single-crop stochastic dynamic pro gramming algorithm, conditional on the optimal seasonal water allocati on of stage one. Optimal daily irrigation decision functions are obtai ned as a function of root-zone soil moisture content and the currently available irrigation water. The methodology is applied to a case stud y characterized by four crops in which both the optimal irrigation app lications and the optimal acreage for each crop are determined.