Calibration and evaluation of a semi-distributed watershed model of Sub-Saharan Africa using GRACE data
Abstract
Irrigation development is rapidly expanding in
mostly rainfed Sub-Saharan Africa. This expansion underscores
the need for a more comprehensive understanding
of water resources beyond surface water. Gravity Recovery
and Climate Experiment (GRACE) satellites provide valuable
information on spatio-temporal variability in water storage.
The objective of this study was to calibrate and evaluate
a semi-distributed regional-scale hydrologic model based
on the Soil and Water Assessment Tool (SWAT) code for
basins in Sub-Saharan Africa using seven-year (July 2002–
April 2009) 10-day GRACE data and multi-site river discharge
data. The analysis was conducted in a multi-criteria
framework. In spite of the uncertainty arising from the tradeoff
in optimising model parameters with respect to two noncommensurable
criteria defined for two fluxes, SWAT was
found to perform well in simulating total water storage variability
in most areas of Sub-Saharan Africa, which have
semi-arid and sub-humid climates, and that among various
water storages represented in SWAT, water storage variations
in soil, vadose zone and groundwater are dominant. The
study also showed that the simulated total water storage variations
tend to have less agreement with GRACE data in arid
and equatorial humid regions, and model-based partitioning
of total water storage variations into different water storage
compartments may be highly uncertain. Thus, future work
will be needed for model enhancement in these areas with inferior
model fit and for uncertainty reduction in componentwise
estimation of water storage variations.
Origin : Publisher files allowed on an open archive
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