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The water movement research in irrigation districts is important for food production. Many hydrological models have been proposed to simulate the water movement on the regional scale, yet few of them have comprehensively considered processes in the irrigation districts. A novel physically based distributed model, the Irrigation Districts Model (IDM), was constructed in this study to address this problem. The model combined the 1D canal and ditch flow, the 1D soil water movement, the 2D groundwater movement, and the water interactions among these processes. It was calibrated and verified with two-year experimental data from Shahaoqu Sub-Irrigation Area in Hetao Irrigation District. The overall water balance error is 2.9% and 1.6% for the two years, respectively. The Nash–Sutcliffe efficiency coefficient (NSE) of water table depth and soil water content is 0.72 and 0.64 in the calibration year and 0.68 and 0.64 in the verification year. The results show good correspondence between the simulation and observation. It is practicable to apply the model in water movement research of irrigation districts.

Percolation is one of the important factors in the field water cycle, which affects designing irrigation schedules and increasing water productivity. However, the measurement of percolation is both costly and time-consuming. This study established a point-scaled system dynamic model (SDM) for water movement in the root zone of winter wheat in Shijin Irrigation District (SID) and proposed a semi-distributed method to extend the SDM from the point to regional scales (SM). Observations of soil moisture of the root zone (0-2 m) of winter wheat from 2007 to 2009 were used to evaluate the SDM and SM. Both could accurately simulate soil water movement during the winter wheat growth period (R 2 > 0.6, RMSE < 0.032). Meanwhile, three extreme scenarios and sensitivity analysis were also applied to ensure the stability and plausibility of the SDM. The distribution of percolation indicated that irrigation was the main reason for percolation. Furthermore, well irrigation reduced the percolation when compared with canal irrigation. Meanwhile, wells were the main water source (56.3%) for the SID and percolation consumed about 22.1% income water. Future study should focus on improving simulation accuracy for spatial variability and consider the lateral exchange of soil water for regions with hills and mountains.