Coupling optimization model embedded groundwater dynamic model for distribution of pumping wells in well irrigation area

Abstract: It is important to study the method of well layout to reduce the irrigation energy consumption and to promote the sustainable utilization of water resources. This paper aimed to explore the suitable layout method of well to reduce the water consumption in well-irrigation area. The optimization model of well layout was constructed with the minimum cost of water intake, in which the groundwater dynamic model (Modflow-2000) was embedded. And the data were exchanged through the common parameters of the 2 models, thus forming the coupling model of well layout. Based on the measured data, the trend of the observation value of the water level was consistent with that of the calculated value at different time after the corresponding parameters of the model were determined. And the mean value of the absolute relative error was 0.88%, and RMSE (root mean square error) value was 0.135 3 m, which could meet the accuracy requirements of the optimal allocation of groundwater resources. It showed that the model could reflect the actual change trend of groundwater level in irrigation area. Finally, taking Tongliao well-irrigation area in Inner Mongolia as the research object, the golden section search method was used to find the optimal positions of the pumping wells. The fluctuation of the water level in wells showed that the irrigation quota in the research area was too large and the irrigation water should be reduced to keep the water resource balance. The results of single well optimization were different from those of the existing well-spacing method. It was found that there were no irrigation wells in the northeastern uncultivated land and villages, and the optimal well location was not in the center position of adjacent 2 wells in the single well optimization results. From the results of global optimization, there was a great change in the distribution of wells compared with the current method of well spacing. And the cumulative value of drawdown in single water extraction could reduce by 5.96 m, and the average value of drawdown could reduce by 0.134 m, which had a certain effect on the decrease of energy consumption in the community. The groundwater movement is a complex system and the model generalization is simpler. Moreover, there is a certain gap with the real flow field. But the application of the coupling model to the optimization of the distribution of well group can also be explained to some extent. The optimization process of single well has reached automatic optimization, and the Modflow-2000 model averagely needs to be operated 10 times in single operation. Meanwhile, the time for single well is about 8 min long. But the process of multi-well optimization is cumbersome. If the model scenario is set to the foundation pit dewatering and the well is set around the foundation pit, the coupling model can optimize the dewatering of the foundation pit; if the water injection is adjusted, the coupling model can also optimize the layout of the artificial recharge well.