Incorporating vegetation dynamics noticeably improved performance of hydrological model under vegetation greening

Numerous hydrological models calculate actual evaporation as a function of potential evaporation (PET) and soil moisture stress. There are some limitations for such empirical equations since they do not consider vegetation changes, and therefore cannot account for the different responses of soil evaporation and plant transpiration to changes in environmental factors and cannot be used for evaluating the impacts of vegetation changes. Here, we investigated whether incorporating a physically based evaporation scheme into a grid-based hydrological model can improve the accuracy of hydrological simulations. The original and modified hydrological models were evaluated in a basin which has experienced rapid vegetation greening. The model evaluations were performed using streamflow observations, soil moisture observations and water balance-based evaporation estimates. Results indicated that the modified model can provide better evaporation simulations than the original model during the period of vegetation greening. The streamflow and soil moisture simulations by the modified model over the same period benefitted significantly from the improvement in evaporation simulations and exhibited better consistency with in situ observations than the original model. This study underscores the importance of including vegetation change information in evaporation estimates and demonstrated that the physically based evaporation equation can be used in hydrological models to improve the hydrological simulations under vegetation greening conditions.