PlR abstract by HC12091410117

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									 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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