Assessing the contributions of human activities to runoff and sediment transport change: A method for break point identification in double mass curves based on model fitting

Abstract

Study regionThe upper Yellow River basin, the Wuding River basin, and the Xinshui River basin in China. Study focusThe double mass curve (DMC) is a widely used tool for assessing the contributions of human activities to runoff and sediment transport change. Scientifically identifying break points in the DMC is crucial for the assessment of human activities contribution. This study proposes a DMC break point identification method using model fitting and applies it to three watersheds with different human disturbance intensities, while also highlighting issues that should be considered in the application of DMC. New hydrological insights for the regionCompared to the baseline period, the runoff transport at Toudaoguai, Baijiachuan, and Daning stations decreased by 36.25 %, 43.68 %, and 51.17 %, with human activities contributing 109.64 %, 102.45 %, and 107.85 %, respectively. Human activities contribution was underestimated by 7.21 %, 6.88 %, and 14.45 %, respectively when using break point identification methods only based on runoff. Additionally, the trends in runoff (sediment) transport may not perfectly align with when human activities occur. The effect of human activities and climate change on runoff and sediment transport is not quantified in absolute terms, the human contributions calculated by DMC methods are only relative. The findings of this study can provide a scientific reference for the application of DMC to calculate the contribution of human activities to runoff and sediment transport change.