Simulation of water and salt transport in the Kaidu River Irrigation District using the modified SWAT-Salt

Soil salinization is the major factor affecting the sustainable development of agriculture in the Kaidu River Irrigation District (KRID) in Xinjiang Province, China. To better understand water and salt variation regularity in the KRID, this study established a watershed-scale distributed water and salt transport model for the KRID based on the new Soil and Water Assessment Tool with a salinity module (SWAT-Salt). Its point source salt module and irrigation water salt module were modified in the study to obtain more accurate simulation results. Based on evaluation indices, the simulation results of streamflow, salt loading, and crop yield showed that the modified model can more accurately depict water and salt transport processes in the KRID and has good applicability. According to the simulation results, the average annual amount of water and salt entering Bosten Lake through the drainage canal accounted for 15 % and 51 %, reaching 4.29 x 108 m3 and 57.87 x 104 t respectively. The drainage and salt discharge during winter irrigation accounted for 69 % and 74 %, reaching 2.95 x 108 m3 and 42.47 x 104 t, respectively. However, the regions along Bosten Lake had high groundwater and soil salinity, facing a risk of increased salinization and necessitating land or water management to decrease salinization. In conclusion, the modified SWAT-Salt can be applied in agricultural irrigation areas with more diverse irrigation sources and is a useful tool for investigating and assessing watershed-scale salinization, as well as implementing targeted management strategies to reduce salinization.