Evaluating functions of the passive storage on modeling hydrological and isotopic processes

To explore the influence of passive storage and isotope information on model accuracy and uncertainty, we developed a coupled flow-isotope model with hillslope-depression units and fast-slow flow systems. The new model was applied to simulate the discharge and isotope process in the Chenqi catchment, which is located in Guizhou Province of south-western China. The simulation results of 14 different schemes (adding passive storage to different units and flow systems of the model) suggested that passive storage can significantly improve the accuracy of isotope simulation and adding passive storage to the hillslope unit is the best scheme. The maximum simulation accuracy Kling-Gupta efficiency of the best model for both discharge and isotope could reach 0.8 and 0.69. Through the comparison and analysis between the calibration results of targeting discharge and isotope showed that isotope information has a certain constraint effect on the model parameters and the internal apportionments of hydrological components. Together, the number and location of passive storage significantly affect the simulation accuracy of isotopes and the constraint effect of isotopes on the uncertainty of the model.