In the past several decades, climate change and human activities have influenced hydrological processes, and potentially caused more frequent and extensive flood and drought risks. Therefore, identification and quantification of the driving factors of runoff variation have become a hot research area. This paper used the trend analysis method to show that runoff had a significant downward trend during the past 60 years in the Second Songhua River Basin (SSRB) of Northeast China. The upper, middle, and lower streams of five hydrological stations were selected to analyze the breakpoint of the annual runoff in the past 60 years, and the breakpoints were used to divide the entire study period into two sub-periods (1956–1974 and 1975–2015). Using the water–energy coupling balance method based on Choudhury–Yang equation, the climatic and catchment landscape elasticity coefficient of the annual runoff change was estimated, and attribution analysis of the runoff change was carried out for the Fengman Reservoir and Fuyu stations in SSRB. The change in potential evapotranspiration has a weak effect on the runoff, and change in precipitation and catchment landscape were the leading factors affecting runoff. Impacts of climate change and land cover change were accountable for the runoff decrease by 80% and 11% (Fengman), 17% and 206% (Fuyu) on average, respectively; runoff was more sensitive to climate change in Fengman, and was more sensitive to catchment landscape change in Fuyu. In Fengman, the population was small, owing to the comparatively inhospitable natural conditions, and so human activities were low. However, in Fuyu, human activities were more intensive, and so had more impact on runoff for the Lower Second Songhua River compared to the Upper Second Songhua River.

中文翻译：

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量化气候变化和当地人类活动对第二松花江流域径流下降的贡献

在过去的几十年里，气候变化和人类活动对水文过程产生了影响，并可能导致更加频繁和广泛的水旱灾害风险。因此，径流变化驱动因素的识别和量化成为研究的热点。本文采用趋势分析方法表明，东北第二松花江流域（SSRB）近60年来径流呈显着下降趋势。选取5个水文站的上、中、下游河流，分析近60年年径流量的断点，利用断点将整个研究期划分为两个子期（1956-1974年和1975年） –2015）。基于Choudhury-Yang方程的水能耦合平衡方法，估计了年径流变化的气候和流域景观弹性系数，并对SSRB丰满水库和扶余站的径流变化进行了归因分析。潜在蒸散量的变化对径流的影响较弱，降水和流域景观的变化是影响径流的主导因素。气候变化和土地覆盖变化的影响导致径流平均分别减少80%和11%（丰满）、17%和206%（扶余）；丰满地区径流对气候变化更为敏感，扶余地区对集水区景观变化更为敏感。丰满地区人口稀少，自然条件相对恶劣，人类活动较少。然而，在扶余，人类活动更加密集，