Abstract
Quantifying the uncertainty linked to the degree to which the
spatio-temporal variability of the catchment descriptors (CDs), and
consequently calibration parameters (CPs), represented in the
distributed hydrology models and its impacts on the simulation of
flooding events is the main objective of this paper. Here, we introduce
a methodology based on ensemble approach principles to characterize the
uncertainties of spatio-temporal variations. We use two distributed
hydrological models (WaSiM and Hydrotel) and six catchments with
different sizes and characteristics, located in southern Quebec, to
address this objective. We calibrate the models across four spatial
(100, 250, 500, 1000 $m^2$) and two temporal (3 hours and 24 hours)
resolutions. Afterwards, all combinations of CDs-CPs pairs are fed to
the hydrological models to create an ensemble of simulations for
characterizing the uncertainty related to the spatial resolution of the
modeling, for each catchment. The catchments are further grouped into
large ($>1000 km^2$), medium (between 500 and 1000
$km^2$) and small ($<500km^2$) to examine multiple
hypotheses. The ensemble approach shows a significant degree of
uncertainty (over $100\%$ error for estimation of
extreme streamflow) linked to the spatial discretization of the
modeling. Regarding the role of catchment descriptors, results show that
first, there is no meaningful link between the uncertainty of the
spatial discretization and catchment size, as spatio-temporal
discretization uncertainty can be seen across different catchment sizes.
Second, the temporal scale plays only a minor role in determining the
uncertainty related to spatial discretization. Third, the more
physically representative a model is, the more sensitive it is to
changes in spatial resolution. Finally, the uncertainty related to model
parameters is dominant larger than that of catchment descriptors for
most of the catchments. Yet, there are exceptions for which a change in
spatio-temporal resolution can alter the distribution of state and flux
variables, change the hydrologic response of the catchments, and cause
large uncertainties.