Climatic and anthropogenic controls on contemporary and historic sediment sources in a lake-connected watershed: Insights from a hierarchical geochemical and compound-specific stable isotope (CSSI) fingerprinting approach

Understanding historical sediment sources and their drivers is essential for effective watershed management. This study provides a novel, century-scale assessment of sediment source dynamics by integrating geochemical and compound-specific stable isotope (CSSI) fingerprinting in the Zarivar Lake watershed, Iran. We measured tracers in potential sources, riverine sediments, and a lake sediment core. Consensus Ranking (CR) and Consistent Tracer Selection (CTS) were used to optimize the tracer combinations for robust source apportionment. This integrated approach identified channel banks (0.39 ± 0.09), uncultivated subsoil (0.29 ± 0.10), and irrigated farming (0.16 ± 0.07) as the dominant sediment sources from 1950s to 2018. Four distinct episodes of sedimentation fluctuations were identified: (i) an early-1930s peak linked to channel modifications; (ii) an early-1940s peak associated with extreme rainfall and mass movements; (iii) mid-1970s to 1980s peaks driven by deforestation and climatic extremes; and (iv) a sharp post-2008 decline following check dam construction, demonstrating the efficacy of sediment flux reduction. The findings reveal that changes in sediment loads were primarily governed by anthropogenic activities, while precipitation often acted as the primary amplifier of these impacts. This research underscores the power of a hierarchical geochemical-CSSI approach to provide a source-specific, century-scale perspective that is critical for designing effective conservation strategies in anthropogenically modified watersheds facing climate change.