Abstract:
Study region: This study was conducted in Soutloop River Catchment, Northern Cape, South
Africa.
Study focus: Although hydrologic models play a critical role in the management of natural resources
in arid areas, their application is challenged by the scarcity of data for calibration and
validation. Therefore, this study aimed at to configure, calibrate and validate SWAT model in a
data-scarce catchment by using the regionalization with physical similarity approach. This approach
uses dual calibration and validation procedure, i.e., one in the donor catchment (by using
SWAT-CUP (SWAT Calibration and Uncertainty Programs) and the other on the study catchment
(by manual calibration and verification).
New hydrological insights for the region: Based on the sensitivity analysis, sixteen parameters were
calibrated by SWAT-CUP. The result from the uncertainty analysis indicated acceptable values of
both the R-factor (0.8**) and P-factor (0.7**). The model performance evaluation also showed
acceptable ranges of values (e.g., NS was 0.76** and R2 was 0.78**). However, the main calibration
and validation process was conducted outside the target catchment, though it was assumed
that the donor and target catchments have similar hydrological responses. Therefore, the
study suggested further inspection methods to minimize the model uncertainty in the study
catchment. This study enables researchers to exploit the river eco-regional classifications of
South Africa to apply hydrologic models to estimate the components of water balance in arid/
semi-arid catchments.
