Simulation And Applications Of Maize Evapotranspiration Base On SIMETAW Model

Accurate estimatemation of crop evapotranspiration is importantfor improving the regional agricultural water use efficiency, which is great significant for rationally use of water resources. In this study, we checked and modified the SIMETAW Model with the research result of field experiment in Fuxin of Liaoning province. The maize evapotranspiration of this region was simulated and analysed with the validated modelThe main research conclusions showed as follows:(1) By comparing the data of the field experiment with simulation result, the difference between the simulation result and the meaused result is error allowed, which indicated that the modified SIMETAW Model can simulate the change course of Maize Evapotranspiration (ETC) accurately, and the model couble be practicable in Fuxin erea.(2) The simulation for maize evapotranspiration (ETC) in different year shows that the variation of maize ETC is bigger in wet year, while is the least in normal year; the level of profit and loss is-26.3% in poor rain years,-10.8% in normal years, and 15.2% in wet years; The simulation for effective rainfall (ET,) and irrigation amount (ETaw) in different years shows the maize ETr is 365.7 mm in wet years, 309.8 mm in nomal rain years, and 253.8 mm in dry years; From the season point, the water loss in June, July and August is the least, slightly surpluse in July.(3) With couple analysis based on the precipitation and water-demand of ETC simulation shows that across different years, the change of the coefficient of water-demand simulation month by month is basically consistent. However, the couple degree of the precipitation and water-demand is inconsistent in the same year. In the wet years, both the coefficient of water-demand simulation and the couple degree of precipitation and water-demand in each month distribute as a parabola type, and they are basic anastomosis, all with a peak value as 85.08% in July; in normal year type, both the couple degree of precipitation and water-demand in each month decrease to some degree, and reach the peak value in advance in June, which results in the inconsistent of both the couple degree of precipitation and water-demand and the coefficient of water-demand simulation, and the couple degree decrease to 73.57% in the entire grow season.(4) The estimate on yield and economic benefit under different model years shows that with the increase of precipitation, irrigation yield drops slowly, rainfed yield inceases gradually. When the precipitation in grow season exceed 500mm, the irrigation and rainfed yield is gradually consistent. In the dry year, the increase potential of irrigation is larger, higher irrigation production can be obtained if it is irrigated timely and properly. When the precipitation is below 300mm (accumulated probability as 75%), rainfed yield is relatively low.(5) The simulation with SIMETAW model on ET0, ETc, ETr, ETaw under different climates shows big difference, which indicates that the climate change result in the maize being sensitive to water, and active measures should be carried out to resolve the bad effect on maize production from climate change.