Geoscience Reference
In-Depth Information
GCMs. It is therefore obvious that the GCMs cannot explicitly capture the fine
scale structure that characterizes climate variables in many regions of the world
that is required to run impact models. This becomes particularly problematic for
important climate variables like precipitation that have high variability in space and
time. Due to their coarse spatial resolutions and their inability to include mesoscale
atmospheric features in their large scale circulation, the GCMs do not simulate the
precipitation fields with adequate fine scale details to be applied to impact models
such as hydrological models. Hence, before the GCM output information of certain
key variables like rainfall can be used to drive the impact models at a regional or
a local scale, there is an intermediate step which requires the 'downscaling' of this
large scale GCM information to regional scale information. One of the techniques
that is employed to this end is what is called as regional climate modelling that
uses a high resolution limited area climate model, also called Regional Climate
Model (RCM), for climate simulations. Later, the output from this RCM, usually
precipitation and temperature, are used as input for hydrological models.
This chapter describes a study that assesses hydrological responses over a couple
of river basins in one of the most climate vulnerable regions, the Mekong River
basin in Southeast Asia. This study uses the output of a regional climate model as
the input to the popular hydrological model Soil Water Assessment Tool (SWAT).
Sensitivity analysis has been carried out to sort out the most affected parameters
to modelling scheme and observed discharge. Shuffled Complex Evolution (SCE)
algorithm is employed to calibrate SWAT model's most sensitive parameters.
Minimum discrepancy between the observed and the simulated runoff results in an
optimal set of values for the calibration parameters.
The following section describes the study region, the Sesan catchment, which is
a small part of the Lower Mekong Basin. The hydrological model and the regional
climate model that were used for this study and the modelling approaches are also
described.
17.2
Study Catchment and Hydrological Model
17.2.1
Sesan Catchment
The catchment considered in this study is the Sesan catchment, lying over the
central highland region of Vietnam between
107
ı
19
0
Eand
108
ı
38
0
Eand
13
ı
33
0
N
15
ı
15
0
N. Together with SrePok and SeKong rivers, the catchment forms
the main river system of Sub-Area 7 (SA7) of Lower Mekong Basin. Detailed
information about the SA7 region is available from the Mekong River Commission
and
Search WWH ::
Custom Search