Critical review of SWAT applications in the upper Nile basin countries
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Date
2012
Authors
Kilonzo, Fidelis
Griensven, A. van
Ndomba, P.
Yalew, S.
Journal Title
Journal ISSN
Volume Title
Publisher
European Geosciences Union (EGU) [Society Publisher]
Abstract
The Soil and Water Assessment Tool (SWAT) is
an integrated river basin model that is widely applied within
the Nile basin. Up to date, more than 20 peer-reviewed papers
describe the use of SWAT for a variety of problems in
the upper Nile basin countries, such as erosion modelling,
land use and climate change impact modelling and water resources
management. The majority of the studies are focused
on locations in the tropical highlands in Ethiopia and around
Lake Victoria. The popularity of SWAT is attributed to the
fact that the tool is freely available and that it is readily applicable
through the development of geographic information
system (GIS) based interfaces and its easy linkage to sensitivity,
calibration and uncertainty analysis tools. The online
and free availability of basic GIS data that are required
for SWAT made its applicability more straightforward even
in data-scarce areas. However, the easy use of SWAT may
not always lead to appropriate models which is also a consequence
of the quality of the available free databases in these
regions. In this paper, we aim at critically reviewing the use
of SWAT in the context of the modelling purpose and problem
descriptions in the tropical highlands of the Nile basin
countries. To evaluate the models that are described in journal
papers, a number of criteria are used to evaluate the model
set-up, model performances, physical representation of the
model parameters, and the correctness of the hydrological
model balance. On the basis of performance indicators, the
majority of the SWAT models were classified as giving satisfactory
to very good results. Nevertheless, the hydrological
mass balances as reported in several papers contained losses
that might not be justified. Several papers also reported the
use of unrealistic parameter values. More worrying is that
many papers lack this information. For this reason, most of
the reported SWAT models have to be evaluated critically.
An important gap is the lack of attention that is given to the
vegetation and crop processes. None of the papers reported
any adaptation to the crop parameters, or any crop-related
output such as leaf area index, biomass or crop yields. A
proper simulation of the land cover is important for obtaining
correct runoff generation, evapotranspiration and erosion
computations. It is also found that a comparison of SWAT
applications on the same or similar case study but by different
research teams and/or model versions resulted in very
different results. It is therefore recommended to find better
methods to evaluate the representativeness of the distributed
processes and parameters (especially when land use studies
are envisaged) or predictions of the future through environmental
changes. The main recommendation is that more details
on the model set-up, the parameters and outputs should
be provided in the journal papers or supplementary materials
in order to allow for a more stringent evaluation of these
models.
Description
doi:10.5194/hess-16-3371-2012
Keywords
Citation
Hydrology and Earth System Sciences (Impact Factor: 3.59). 09/2012; 16(9):3371-3381. DOI: 10.5194/hess-16-3371-2012