Optimizing Ecological Water Use: Simulation of Soil Water Transport in Desert Riparian Forests of the Lower Tarim River Under Overflow Irrigation

To enhance the utilization efficiency of limited ecological water, this study conducted field ecological irrigation experiments in a typical desert riparian forest in the lower reaches of the Tarim River. Based on the experimental data, a soil water transport model under the overflow irrigation mode was constructed using the HYDRUS-2D (version 2.04) model. Based on the model, numerical simulation scenarios of different irrigation schemes were designed to provide key evidence for the scientific utilization of water resources in the ecological restoration of desert riparian forests. Simulation results indicate that (1) more irrigation water does not necessarily yield better results. When the total irrigation volume is the same, conducting overflow irrigation in two separate applications significantly outperforms a single concentrated irrigation in terms of soil moisture replenishment and maintenance, with an optimal interval of 20 h between applications. (2) For single overflow irrigation, the optimal water depth is 5 cm. (3) For two-stage irrigation, the available water resources and core objectives must be considered. When water is plentiful, and it is necessary to replenish moisture in the lower soil layers, the 5 cm + 5 cm scheme is optimal; if irrigation water is limited, the 3 cm + 3 cm scheme is more efficient. These schemes can effectively activate the seed bank in the surface soil while supplying water to the root systems of desert riparian vegetation, thereby promoting the restoration and growth of desert vegetation and achieving the goal of ecological sustainability.