Effects of precipitation increase and land use changes on hydrological and sediment dynamics in the Nenjiang River basin, Northeast China

The Nenjiang River basin, located in Northeast China, is a vital agricultural region characterized by dynamic hydrological and sediment processes influenced by climate variability and human activities. This study explores the interplay between precipitation increases and land use changes on runoff and sediment dynamics using data from 8 hydrological and 12 meteorological stations over a 50-year period (1970 to 2020). Employing statistical analysis, the double mass curve method, and Budyko theory, the research aims to identify trends, regional differentiation, and contributing factors. The results reveal significant spatial and temporal variability in runoff and sediment trends. In the basin’s upper reaches, increased precipitation is the dominant driver of enhanced runoff, accounting for more than 60% of the observed changes. Conversely, in the middle and lower reaches, land use changes, particularly agricultural expansion and urbanization, emerge as the primary contributors to altered runoff and sediment yields. The study highlights 1998 as a pivotal year because a catastrophic flood reshaped river morphology, altering sediment transport pathways and intensifying the runoff-sediment relationship. Additionally, land reclamation in the 1980s and urbanization after 2010 markedly influenced the basin’s hydrological and sedimentary processes, both with positive effects, such as improved flood management in some areas, and negative consequences, including accelerated soil erosion and sediment deposition in others. These changes pose challenges for sustainable land and water resource management in the black soil region, which is critical for China’s food security. This study demonstrates the persistent impact of extreme flood events on the hydro-sedimentary dynamics of a large agricultural basin. These findings offer valuable references for managing river systems under the dual pressures of land use change and climate extremes.