Abstract
Although soils form an integral part of landscape hydrological processes, the importance of soil information in hydrological modelling is often neglected. This study investigated the impact of soil information on streamflow modelling accuracy and hydrological process representation. Two different levels of soil information were compared to long-term streamflow in the upper Goukou catchment (230 km2), South Africa, over a period of 23 years using the Soil Water Assessment Tool (SWAT+). The land-type soil map (LTSM) dataset was less detailed and derived from the best, readily available soil dataset for South Africa currently. The hydrological soil map (HSM) dataset was more detailed and was created using infield hydropedological soil observations combined with digital soil-mapping techniques. Monthly streamflow simulation was similar for both soil datasets, with Nash–Sutcliffe efficiency and Kling–Gupta efficiency values of 0.57 and 0.59 (HSM) and 0.56 and 0.60 (LTSM), respectively. It is, however, important to assess through which hydrological processes were these streamflow values generated as well as their spatial distribution within the catchment. Upon further assessment, the representation of hydrological processes within the catchment differed greatly between the two datasets, with the HSM more accurately representing the internal hydrological processes, as it was based on infield observations. It was concluded that hydropedological information could be of great value in effective catchment management strategies since it improves representation of internal catchment processes.
Highlights
Soils are a primary control mechanism in determining hydrological processes within a landscape by partitioning precipitation into the different components of the water balance.This is the result of the ability of soils to absorb, store, and transmit water at different spatial and temporal scales [1]
Hydrological processes in the soil determine the volume, variability, and residence times of water resources within a landscape, which in turn affects the functionality and diversity of ecosystems [2]
The land-type soil map (LTSM) dataset contained a greater variety of soils (11 soil types vs. 6 in the hydrological soil map (HSM) dataset) and a wider array of hydrological soil properties based on pedotransfer functions
Summary
Soils are a primary control mechanism in determining hydrological processes within a landscape by partitioning precipitation into the different components of the water balance. This is the result of the ability of soils to absorb, store, and transmit water at different spatial and temporal scales [1]. Hydrological processes in the soil determine the volume, variability, and residence times of water resources within a landscape, which in turn affects the functionality and diversity of ecosystems [2]. Soil information employed in hydrological modelling has remained relatively crude compared
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