Monday, November 13, 2006 - 11:00 AM
99-6
Hydropedological Applications in the WRB: An Example from the Weatherley Catchment, South Africa.
Soils play a dominant role in the hydrological system. Managing water supply therefore requires intimate knowledge of soils and its impact on water in the landscape. The World Reference Base (WRB) defines various reference soil groups, but these are mainly aimed at applications for arable agriculture. The purpose of this paper is to determine the feasibility of hydropedological interpretations for WRB classification, based on data from the Weatherley catchment in the northern Eastern Cape Province of South Africa. Twenty-eight soil profiles were classified based on the WRB, their water content was monitored weekly for nine years (1997-2005), and the annual duration of water saturation in each soil was calculated. One Alisol, 1 Luvisol, 2 Albeluvisols, 2 Arenosols, 3 Cambisols, 3 Lixisols, 3 Planosols, 4 Ferralsols and 9 Gleysols were identified in this catchment. Depth-weighted whole profile average annual duration of water saturation increased in the following order: Arenosols 3% ± 2% (mean ± standard error), Cambisols 20% ± 1%, Alisols 28% ± 1%, Ferralsols 28% ± 3%, Albeluvisols 35% ± 6%, Luvisols 43% ± 7%, Gleysols 55% ± 2%, Lixisols 55% ± 2%, and Planosols 57% ± 1%. Note that these soils had similar climate and vegetation within the study catchment. Our data indicated that Arenosols are excessively drained and that Gleysols, Lixisols and Planosols were continuously wet, irrespective of inter-annual rainfall variation. Water saturation in Cambisols, Alisols, Ferralsols, Albeluvisols, and Luvisols was not significantly different. Water saturation in Luvisols and Albeluvisols were highly dependent on inter-annual rainfall, wetting excessively during wet years and drying considerably during dry years, while water saturation in Cambisols, Alisols and Ferralsols seemed to be less dependent on annual rainfall variation. It appears that the WRB classification offers sufficient differentiation to allow for hydropedological interpretations. Future research should focus on the quantification of these relationships.
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