Model calibration using hydropedological insights to improve internal
hydrological processes within SWAT+
Abstract
Soils affect the distribution of hydrological processes by partitioning
precipitation into different components of the water balance. Therefore,
understanding soil-water dynamics at a catchment scale remains
imperative to future water resource management. In this study the value
of hydropedological insights to calibrate a processes based model. Soil
morphology was used as soft data to assist in the calibration of the
SWAT+ model at five different catchment sizes (48 km
2, 56 km 2, 174 km
2, 674 km 2 and 2421 km
2) in the Sabie River catchment, South Africa. The aim
of this study was to calibrate the SWAT+ model to accurately simulate
long-term monthly streamflow predictions as well as to reflect internal
soil hydrological processes using a procedure focusing on hydropedology
as a calibration tool in a multigauge system. Results indicated that
calibration improved streamflow predictions where R 2
and Nash-Sutcliffe Efficiency (NSE) improved substantially, R
2 improved by 2 to 8% and NSE from negative
correlations to values exceeding 0.5 at four of the five catchment
scales compared to the uncalibrated model. Results confirm that soil
mapping units can be calibrated individually within SWAT+ to improve the
representation of hydrological processes. Particularly, the spatial
linkage between hydropedology and hydrological processes, which is
captured within the soil map of the catchment, can be adequately
reflected within the model structure after calibration. This research
should lead to an improved understanding of hydropedology as soft data
to improve hydrological modelling accuracy.