Characteristics and influential Factors of Water and Sediment Evolution in Typical Basins of the Lower Reaches of the Minjiang River

To scientifically guide soil erosion control and water resource development in the lower Minjiang River, data from the Yongtai Hydrological Station (1982—2023) in the lower Dazhangxi River Basin were analyzed to exa-mine the distribution and temporal trends of water and sediment. Cyclical characteristics were also investigated across multiple time scales, and the relative contributions of climate change and human activities were quantified. The results reveal an abrupt change in both runoff and sediment transport rate in 2003. Runoff dynamics were primarily influenced by total rainfall, while sediment transport was mainly controlled by erosive rainfall. Compared to the baseline period (1982—2002), the change period (2003—2023) exhibited a 21.6% reduction in runoff and a 60.7% decrease in sediment transport rate, with marked wet-dry alternations. Human activities were the dominant factor driving these reductions, accounting for over 95% of the decreases in both water and sediment. Sediment concentration also declined during the change period. In summary, both water and sediment loads in the Dazhangxi River Basin showed decreasing trends from 1982 to 2023, with a more pronounced decline in sediment transport rate. Thus, human activities should be prioritized in future strategies for water and sediment management and deve-lopment in the basin.