Simulation and analysis of return flow at the field scale in the northern rice irrigation area of China

To study variations in the field return flow, a field water balance model was established according to the water balance principle, and the field return flow was simulated using system dynamics and tested with field-measured data collected in a trial district in the Hu Lanhe irrigation area in 2016. The main conclusions are as follows: trends of the simulated and measured field water storage and field runoff were consistent. The daily error range between the simulated and measured field water storage values was (−0.1996, 0.2034) mm, and the daily error range between the simulated and measured field runoff values was (−0.2183, 0.1853) mm. Comparison of the trends among the water inflow, the surface return flow, the underground return flow and the total return flow revealed that the greater the water inflow was, the more similar the trends of the surface return flow and total return flow were, with no obvious change in the underground return flow. The total return flow increased with increasing field ridge length and decreased with increasing field ridge height and width. The range of the return flow coefficient of irrigation in 2011˜2016 was (0.5825, 0.6395), and the range of the return flow coefficient of irrigation and precipitation was (0.2734, 0.3386); the impact of irrigation water on the return flow was greater than that of precipitation. The research results are significant to the evaluation and analysis of field return flow and the management of agricultural irrigation water and provide a comparative reference for the study of return water in other areas.