“十四五”时期，我国生态环境保护进入了减污降碳协同治理的新阶段。流域承载了经济社会发展的巨大负荷，排放和消纳了大量温室气体和污染物，在流域尺度上推进减污降碳协同成为当前备受关注的问题。本文阐述了流域尺度上温室气体和污染物的协同减排机制，将流域划分为人工生态系统和自然生态系统，列举了不同生态系统间减污降碳协同的主要路径和重点技术，并以黄河流域、长江流域为例，分析了在流域尺度上减污降碳协同技术的具体应用情况。在负排放技术、农业面源污染控制技术和水体富营养化修复技术的支撑下，本文提出了细化流域水生态环境保护标准、建立监控预警和风险防控系统，构建污染源和温室气体排放源综合整治体系、健全流域管控机制，加大科技支撑力度、积极开展气候变化国际合作等对策建议，助推我国流域减污降碳协同。

China's eco-environmental protection enters a new stage of synergizing the reduction of pollution and carbon emissions during the 14th Five-Year Plan period. Watershed bears heavy loads from economic and social development and emits a large amount of greenhouse gases and pollutants. Therefore, synergizing the reduction of pollution and carbon emissions on a watershed scale becomes an issue of concern. This study expounds on the synergistic mechanism for the reduction of greenhouse gases and pollutants, categorizes the ecosystem of a watershed into artificial and natural ecosystems, and proposes the main pathways and key technologies for these ecosystems. Using the Yellow River basin and the Yangtze River basin as examples, specific applications of the key technologies are summarized. Negative emissions technology, agricultural non-point source pollution control technology, and water eutrophication remediation technology should be further developed. Furthermore, three countermeasures are proposed: (1) refining the water ecological environment protection standards and establishing a risk prevention and control system; (2) establishing a comprehensive treatment system for pollution and greenhouse gas emission sources to improve the watershed management and control mechanism; and (3) increasing investment in science and technology and participating in international cooperation on climate change.