Quantifying the changes in solute transport caused by human influence on river connectivity in inland river basins

River connectivity maintains the transport of nutrients, organic matter, and organisms, serving as a crucial link in global and regional biogeochemical cycles. However, understanding the disturbance mechanisms of human activities on river connectivity and the resulting changes in material migration remains a critical knowledge gap. To address the limitations of current research, this study established an integrated observation network in the Shiyang River Basin (SRB). By employing isotope tracing techniques and hydrochemical analysis methods, the study quantitatively assessed the influence and regulatory mechanisms of surface water connectivity on the migration and transport processes of key solutes in the basin. The results show that: (i) river connectivity is significantly enhanced during summer and autumn when rainfall and runoff are higher, leading to a decrease in solute concentrations, while connectivity is notably weakened during winter and spring, resulting in an increase in solute concentrations. (ii) The construction of dams has led to the fragmentation of rivers within the basin, altering the migration pathways of solutes. Consequently, the transport process of solutes from upstream to downstream, towards reservoirs and irrigation areas, has become increasingly significant. The research quantitatively assesses the substantial influence of anthropogenic activities, especially dam construction, on river connectivity and elucidates the mechanisms through which alterations in river connectivity affect the transport of substances. Given the current intensive construction of water conservancy projects in arid region rivers, the natural river connectivity is gradually weakening, and the migration rate of materials is also slowing down accordingly. This change is not conducive to the sustainable development of the basin ecosystem and requires sufficient attention and in-depth research.