Abstract: Investigating the effects of climate change, land use and cover change (LUCC) and increased CO₂ concentration on catchment runoff is important for acquiring an understanding of ecohydrological processes under changing environment at a basin scale. To analyze these effects, a model is developed through coupling a hydrological model (Distributed Time Variant Gain Model; DTVGM), a global terrestrial biogeochemical model for carbon, nitrogen and phosphorus (CASACNP) and a land use Cellular Automata -Markov (CA-Markov) model. The coupled model is then applied to the Luanhe River basin of Northern China. The model performs well during both model calibration and validation processes. The calibrated model is then used to study the effects of climate change, LUCC and CO₂ enrichment on runoff over the basin. Results show the effects of climate change and LUCC on runoff are stronger than that of increased CO₂ concentration. The annual runoff exhibits a decreasing trend for the period 2020—2049, and shows a reduced runoff as compared to the base year for most of the scenarios. The intra-annual analysis shows a decrease in runoff during wetter months and an increase during drier months. The monthly runoff during flood seasons would be more sensitive in the future as compared to non-flooding seasons.