Using hydropedological characteristics to improve modelling accuracy in Afromontane catchments

Abstract

Study region: Three Afromontane catchments in the Cathedral Peak experimental research site, within the uKhahlamba-Drakensberg escarpment, KwaZulu-Natal, South Africa. Study focus: Gaining insight into the hydropedological behaviour of catchments enables a deeper understanding of the unique lateral flow dynamics of a landscape and how these affect the hydrological cycle. This study aimed to highlight the importance of understanding the hydropedological behaviour of soils to improve modelling accuracy. New hydrological insights: Two sets of SWAT+ models were set up for each catchment. The default lateral time, which is the measure of the time required for water to flow through the catchment before being discharged into the stream, was used in the first set up. Specific lateral time inputs, derived from hydropedological soil maps, were utilised in the second model set up and the results compared against observed streamflow. The specific lateral time inputs were based on measured hydraulic properties of the soils coupled with the location of hydrological response units within hydropedological soil maps created for each catchment. The specific lateral time inputs improved modelling accuracy in all statistical parameters used, R2 (i.e., 0.550–0.903), PBIAS (i.e., 19.742–18.239), ST DEV (i.e., 63.42–51.81), NSE (i.e., 0.316–0.864) and KGE (i.e., 0.630–0.807). This study has highlighted that relevant soil information, based on reliable site-specific data, is essential in hydrological modelling.