Zheng Duan

The mountain front recharge (MFR) process significantly influences the movement of water and dissolved organic carbon (DOC) in alpine catchments. However, no existing watershed models can adequately simulate this process, hindering accurate quantification of streamflow and DOC dynamics. To address this gap, this study explicitly incorporated the MFR process into a watershed-scale integrated water–carbon model. The model effectively captured the streamflow and DOC dynamics in a small catchment on the northeast Qinghai-Tibet Plateau, with Nash-Sutcliffe Efficiency values exceeding 0.7 for daily streamflow and 0.5 for monthly DOC concentrations. To our knowledge, this is the first watershed-scale integrated water–carbon model capable of simulating the MFR process in alpine watersheds. The results revealed that the MFR process significantly delayed the DOC export at the catchment outlet compared to the mountain outlet. Specifically, the permafrost-covered mountain area exported 4,172 ± 682 kg yr⁻¹ of DOC with a peak in pre-monsoon. Only 13% of the DOC from the mountain area was directly transported to the catchment outlet, with the remainder entering the alluvial aquifer and later discharged into the mainstream via groundwater. Consequently, the catchment exported 5,412 ± 1,198 kg yr⁻¹ of DOC, with the highest DOC flux observed in summer. These findings highlight the importance of the MFR process in shaping the spatiotemporal patterns of DOC export from catchments.