Spatio‐Temporal Consistency and Variability in Parameter Dominance on Simulated Hydrological Fluxes and State Variables

Abstract Hydrological parameters are used to tailor simulation models to the specific characteristics of a catchment so that models can accurately represent processes under different catchment conditions. In the case of the mesoscale Hydrological Model (mHM), its parameters are estimated via transfer functions using the Multiscale Parameter Regionalization (MPR) approach. In this study, the spatial and temporal variability in the sensitivity of transfer function parameters (TFP) and their relationships to corresponding simulated processes are investigated to understand how these TFP control simulated hydrological fluxes and state variables. Daily dominant model parameters are identified for 102 German catchments as a study domain with temperate climate using a temporally resolved parameter sensitivity analysis. This approach allows the comparison of spatial and temporal variability of TFP dominance. Three simulated hydrological fluxes and one state variable are used as target variables for the sensitivity analysis: runoff, actual evapotranspiration, soil moisture (SM), and groundwater recharge. The analysis leads to consistent and plausible patterns of parameter dominance in space. An evapotranspiration parameter dominates actual evapotranspiration and SM. Runoff and recharge are mainly controlled by soil texture, subsurface, and percolation parameters. The relevance of spatial versus temporal variability varies among model parameters and target variables. In some cases, parameter sensitivities are related to the magnitude of corresponding processes. Low spatial and temporal variability of dominant parameters is explained by MPR. In light of these results, a joint spatio‐temporal analysis is recommended to better understand how model parameters drive simulated states and fluxes in hydrological models to improve process accuracy.