Abstract: Urban rivers face the challenge of maintaining environmental flow to ensure the sustainability of the water environment.Taking Taohuaxi River in Chongqing as a case study, this paper determined the environmental flow using the Tennant method.MIKE11 model was employed to simulate changes in river flow enhancement and water quality improvement under different scenarios.This approach aimed to explore the effects of reclaimed water replenishment on environmental flow and compare it with the inter-basin water transfer scheme.The results indicate that urbanization has increased demands on river flow, while the declining trend in dry season flow has exerted significant pressure on the riverine ecosystem.Reclaimed water replenishment can reduce the frequency of river flow falling below excellent and good standards by 44% and 75%, respectively, thereby significantly alleviating both the severity and duration of water shortages during ecologically sensitive periods.Reclaimed water, with water transfer as supplementation, can ensure that the Taohuaxi River satisfies diverse environmental flow requirements.However, the water replenishment may introduce pollution risks to river sections with good background water quality.The effectiveness of flow replenishment and water quality improvement hinges on the quantity and quality of the replenishing water, particularly the effluent standards of wastewater treatment plants.The findings of this study can serve as a scientific basis for decision-making authorities in the development of sustainable protection plans for urban rivers.The methodologies employed may offer references for river management practices in other cities.