| Most of regions in our country have an arid, semi-arid or semi-humid climate and the water required for crops is obtained mainly through irrigation systems. Water is one of the most important inputs essential for the production of crops. Scheduling water application is very critical to make the most efficient use of irrigation system. The process of water consume of the crop is important to layout and design for irrigation engineering.Irrigation process of paddy is interrelated with precipitation and evaporation in irrigation area. Because data of precipitation and evaporation is basal data of weather station, it can be obtained easily. But the length of precipitation and evaporation is limited usually, this article try to simulate the process of precipitation and evaporation with method of stochastic hydrology by statistical parameter of factual sequence. Through analysis of prevalent stochastic model, seasonal planar AR(1) have advantage of brief framework and ripe theory and method. This model can reflect seasonal variability of precipitation and evaporation preferably. Consequently, this article adopt seasonal planar AR(1) to simulate the process of precipitation and evaporation.The seasonal planar AR(1) form is used in illustration analysis of Zao He irrigation area. Furthermore, the form parameter is calculated, and form can be examined. The examination result indicates that the independence of the sequence residual error and the function of the form satisfy the request. According to the actual circumstance of the irrigation area, the function relation between water required of rice and evaporation from water surface quantity is established, and the process of requirement water of the rice with sequence of precipitation and evaporation is calculated. Then, irrigation scheduling of rice is determined by water balance method, furthermore. Compared with actual series of irrigation water process about rice, the simulated result was in agreement with it.
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