Characteristics and influencing factors of water and sediment changes in Jiaojiang River Basin

Under the influence of climate change and human activities, more and more people pay attention to the changes of runoff and sediment processes. It is of great significance to study the characteristics and influencing factors of water and sediment changes in Jiaojiang River Basin, Zhejiang, China, for ecological protection and high-quality development. Based on the long-term monitoring data of precipitation, runoff, sediment transport, and remote sensing images of the basin, we comprehensively analyzed the evolution characteristics of precipitation, runoff, and sediment transport in the basin using various methods, including linear regression trend analysis of hydrological observation data, catastrophe test of hydrological series by Mann-Kendall catastrophe test, sliding T test, anomaly cumulative curve method, double-cumulative-curve method, and periodic analysis of hydrological series by wavelet and power spectrum. Moreover, the linear regression method was used to estimate the contribution rate of human activities and climate change to the sediment transport change in the river basin. At last, the influence of human activities on the water and sediment change in the river basin was discussed. The results show that 2–3 years, 4–5 years, 8–9 years and 15–18 years of precipitation cycles in the two tributaries; runoff cycles of 2–3 years, 8–9 years, 14–15 years and 18 years; and sediment transport cycles of 2–3 years, 8 years, 12–15 years, and 19 years present in Jiaojiang River Basin. The annual precipitation, annual runoff and annual sediment transport of the tributaries Yongan River and Shifeng River had no significant changes, and the annual sediment transport of Yongan River decreased by 28% in the past 63 years from 1957 to 2021. The contribution rate of human activities to the decrease of sediment transport in Yongan River was 86.5%–98.7%, and that in Shifengxi was 50.3%–83.2%. In addition, reservoir construction played a very good role as a buffer. Significant changes in land use/cover reduced the soil erosion in Jiaojiang River Basin with less sediment generation. The vegetation coverage in watersheds of the two tributaries was gradually increasing, which reduced the sediment yield in the watersheds to some extents.