CHARACTERISATION AND CLASSIFICATION OF HYDROLOGICAL SOILSCAPES OF SOUTH AFRICA PAL le Roux1, JJ van Tol1, BT Kuenene1, SA Lorentz2 and M Hensley1 1 Dept Soil, Crop and Climate Science, University of the Free State 2 School of Bioresources Engineering and Environmental Hydrology, University of KwaZulu- Natal E-mail: LeRouxPA@ufs.ac.za INTRODUCTION Water distribution in the landscape is uneven ranging from freely drained upland, recharge, oxidised and acidic soils; periodically saturated midslope, interflow, redox and variable acid soils and waterlogged wetland, saturation excess responsive, reduced and less acidic soils. These hydrological soil types are topographically linked in a soilscape (hydrosequence, catena or toposequence). The hydrological nature of the soils is interrelated to soil properties including morphology used in soil classification and surveys. The variation in soil water regime is a window to the interaction between the upper and lower vadose zones. Systematic redistribution system implies that systematic hillslope mechanisms in the soil and fractured rock (factors) are controlling processes (flowpaths and storage mechanisms in the soil and fractured rock) which leave very specific signatures in the soil as properties. Therefore, soil maps based on these properties can form the basis for setting up hydrological models for prediction of the hydrological behaviour of catchments. METHODOLOGY Soilscapes (48) on varying geology and in climates varying from arid to sub-humid were surveyed as part of several projects. Soil properties (chemical, water regime and drainage) indicative of control mechanisms, flowpaths and storage mechanisms correlated well with soil and terrain morphology. Conceptual soilscape hydrological response models were developed, characterised and classified according to their measured and inferred hydrological characteristics. RESULTS AND DISCUSSION The relationship of soil properties to hydrology is useful to infer soilscape hydrology as it fit measured data. These soil properties include non-diagnostic properties (lime and base saturation), diagnostic horizons (E and G) and soil forms (Hutton, Cartref). The soilscapes are hydrologically grouped as i) soil flow dominant, ii) fractured rock flow dominant and iii) interactive soil/fractured rock flow. Conceptually group i) soilscapes contributes largely to hydrograph shoulder flow, group ii) more to hydrograph baseflow and group iii) to shoulder and to baseflow. CONCLUSION Hydrological response can be predicted from soil surveys done with the SA soil classification system. Soil maps can contribute significantly to the design of the hydrological response models and predictions in ungauged basins where models cannot be calibrated. Keywords: Hillslope hydrology, hydropedology, soil forms, prediction in ungauged basins.
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