Important factors in land–atmosphere interactions: surface runoff generations and interactions between surface and groundwater

This paper presents two recent improvements on the current version of the three-layer variable infiltration capacity (VIC-3L) model. One is to include the infiltration excess runoff generation mechanism in the variable infiltration capacity (VIC) by considering effects of subgrid spatial soil heterogeneities, which is consistent with the VIC's earlier subgrid spatial variability treatment for the saturation excess runoff process. The other is to dynamically take into account the effects of surface and groundwater interactions on soil moisture, evapotranspiration, and recharge rate. The new version of the VIC model is applied to a watershed of Little Pine Creek near Etna in Pennsylvania for multiple years. Results show that the new version of the VIC properly simulates the total runoff and groundwater table, and that the two processes affect the partition of water budget for the study site. Although the new surface runoff parameterization and the process for surface and groundwater interactions are developed under the context of the VIC model, the framework and methodology presented in this paper could be applied to other land surface models as well.