Large-scale applications and regionalization
of SWAT
A regionalization approach based on the principle of
similarity is attractive for large-scale applications
aimed at evaluating BMPs. For example, it could
support the application of SWAT to analyse different
management options needed for the implementation
of the Water Framework Directive (EC 2000) in
Europe. The calibration of such a comprehensive
model as SWAT is still a challenge despite the availability
of technical tools supporting calibration, such
as SUFI-2 (Yang et al. 2008). The objectives of the
paper by Malagò et al. (2015) in this Special Issue
were: (a) to analyse the spatial variation of calibration
parameter sets in two large regions in Europe, the
Scandinavian and Iberian peninsulas, and (b) to identify
the most important hydrological processes in
these regions. This study belongs to a subset of
SWAT papers focused on regionalization of input
parameters (see SWAT literature database). The
results show that (i) the ranges of calibrated snow
parameters are different in the two regions, (ii) the
temperature and precipitation lapse rates are higher in
Scandinavia than in the Iberian Peninsula, and (iii)
the ranges of calibrated soil parameters are very
different in the two studied regions. In addition, it
was found that differences in spatial patterns of analysed
parameters reflect differences in main runoff
generating mechanisms in the two regions: whereas
in Scandinavia snowmelt produces a bulk of surface
runoff in spring, in the Iberian Peninsula runoff
occurs mainly during intensive storms. In addition,
the study investigated strengths and weaknesses of
the step-wise calibration procedure in SWAT when
applied at the pan-European scale.