Regionalized lumped rainfall-runoff (RR) models have been widely employed as a means of
predicting the streamflow of an ungauged watershed because of their simple yet effective simulation
strategies. Parameter regionalization techniques relate the parameter values of a model calibrated to
the observations of gauged watersheds to the geohydrological characteristics of the watersheds. Thus,
the accuracy of regionalized models is dependent on the calibration processes, as well as the structure
of the model used and the quality of the measurements. In this study, we have discussed the potentials
and limitations of hydrological model parameter regionalization to provide practical guidance for
hydrological modeling of ungauged watersheds. This study used a Tank model as an example
model and calibrated its parameters to streamflow observed at the outlets of 39 gauged watersheds.
Multiple regression analysis identified the statistical relationships between calibrated parameter
values and nine watershed characteristics. The newly developed regional models provided acceptable
accuracy in predicting streamflow, demonstrating the potential of the parameter regionalization
method. However, uncertainty associated with parameter calibration processes was found to be large
enough to affect the accuracy of regionalization. This study demonstrated the importance of objective
function selection of the RR model regionalization.
Keywords: parameter regionalization; regional model; Tank model; ungauged watershed; hydrological modeling; lumped rainfall-runoff simulation