Study On Rational Allocation Of Agricultural Water Resources In Panzhuang Irrigation District Of Texas Based On System Dynamics Simulation

China’s water resources is nearly the lowest per capita in the world and its spatial distribution is very even, which is not matching with farmland distribution. This kind of phenomenon is very standout in many big, middle and small irrigation districts of China, which causes that unreasonable distribution of water resources exists to varying degrees in the many irrigation districts.Based on Khan et al.(2009) and Zhou(2012), soil water balance model established by Khan et al. is improved in the Panzhuang Irrigation District, Dezhou, Shandong Province and differences of cotton water consumption(Evapotranspiration, ET), irrigated water amount and water use efficiencies(WUE) are studied in the upper, middle, lower reaches of the irrigation district on the one hand. On the other hand, a new reasonable allocation model of water resources is established and interactive relationships of surface water and groundwater of wheat,maize and cotton are studied in the upper, middle and lower reaches of the irrigation. On the basis of these, the best irrigation schedule of differently proportional use of surface water and groundwater is analyzed and reasonable allocation of water resources is realized in the in the upper, middle and lower reaches of the irrigation district.Conclusions are as follows through study:(1) Cotton primarily consumed precipitation and irrigation water in its growing seasons.Besides pre-sowing water, cotton usually needed to be irrigated one times during its growth period in majority of years from 2000 to 2009. Mean water consumption of ten years were628.88 mm,626.89 mm and 641.4 mm in the upper, middle and lower reaches of the irrigation district, respectively. Water consumption and WUE were the largest and the least in the lower and middle reaches, respectively, and they are middle in the middle reaches.(2) Based on reasonable allocation model of water resources of the irrigation district and interactive relationships of surface water and groundwater of wheat, maize and cotton,groundwater depth increased very quickly, which caused groundwater depression and increased irrigation cost if crops were irrigated by groundwater only; groundwater depth was shallow and the capillary rise was big, which resulted in water loss if crops were irrigated by surface water only. In order to avoid these adverse effects, joint irrigation of surface water and groundwater had better be used.(3)Under the 8 scenarios, yields and WUE of wheat, maize and cotton were analyzed in the analyzed in the upper, middle and lower reaches by using the reasonable allocation model of water resources of the irrigation district. Based on groundwater depth, water use efficiency and water total amount control, the best irrigation schedule of differently proportional use of surfacewater and groundwater is analyzed and reasonable allocation of water resources is realized in the in the upper, middle and lower reaches of the irrigation district.