Effects of driving factors at multi-spatial scales on seasonal runoff and sediment changes

The changes in runoff and sediment are the most active parts of river systems. Identifying the effect of precip-itation, vegetation coverage (VC), landscape metrics, land-use and land-cover changes (LUCC) on runoff and sediment variations is essential for understanding hydrological processes and the environmental evolution mechanisms of watersheds. This study selected four watersheds located in the Qinling Mountains in China to quantify the effects of different driving forces on runoff and sediment variations at different scales. The results showed that VC increased significantly in the study watersheds (p < 0.05) by more than 16 % since 1990. Obvious increases in forest area were the main features of land use change after 2000. The annual sediment transport and sediment concentration in the wet season showed downward trends. The change of underlying surface contributed more than 58 % to reductions in runoff and sediment concentration in controlled watersheds in Xiangjiaping and Jingziguan. The factors influencing runoff and sediment variations displayed obvious spatial and temporal differences. The 2000 m buffer scale could better explain the runoff and sediment variations than other spatial scales. Rainfall and VC were the main factors affecting runoff and sediment variations at different spatial scales during the wet season, while the aggregation index at the watershed-scale and VC were the main influencing factors in the dry season. Moreover, the intersections between precipitation and landscape pattern, between precipitation and LUCC & VC, and between landscape pattern and LUCC & VC in the dry season and wet season were-31.9 %,-27.6 %,-29.0 % and-18.7 %,-11.1 % and-2.3 %, respectively. Therefore, multi -scale differences in the impact of driving factors and the group relationships between measures should be considered for effective runoff and sediment regulation.