Evaluating Spatiotemporal Variations in the Impact of Inter-basin Water Transfer Projects in Water-receiving Basin

Inter-basin water transfer (IBWT) has been widely applied to solve the water resource crisis in water shortage areas, and its impact on the ecological environment of water-recipient areas has gained increasing attention in recent years. In this study, based on the Soil and Water Assessment Tool (SWAT) model, the average monthly channel flow and water environmental capacity (WEC) with or without IBWT projects were simulated and quantified in the Fenhe River basin of China. The results showed that the IBWT projects significantly improved the flow of 63% of channels, and the increase in the dry season (80%) was much higher than that in the wet season (20%). The changes in the ideal WEC were positively correlated with the channel flow, while the remnant WEC showed different change trends in different channels and seasons. Spatially, the remnant WEC decreased in a few upstream channels and increased in the downstream channels. Seasonally, IBWT projects had different seasonal effects on the remnant WECs of total nitrogen (TN) and total phosphorus (TP). In the dry season, the remnant WEC of TN decreased by 2% after IBWT, while the remnant WEC of TP increased by 140%. In the wet season, the remnant WEC of TN increased by 4%, while the remnant WEC of TP decreased by 80%. Through a long-term simulation of IBWT projects, this study reduced the uncertainties caused by random changes in the hydrological environment. These results could provide effective guidance for management after the construction of IBWT projects.