Developing hydrological response models for selected soilscapes in the weatherly catchment, Eastern Cape Province

Abstract

Soil acts as a first order control and determines the flowpaths of water exiting a catchment. The long term interactive relationship between water and parent material has resulted in present soil morphology. The soil chemical properties react faster than morphological properties to a change in pedological processes predominantly controlled by the water regime in soil. Flowpath characteristics, from very fast to very slow, determines the resultant soil chemistry. Soils can act as flow path or as a storage mechanism of water in the soilscape. Soils were grouped according to their hydrological response. Recharge soils are soils, which serve as conduits of infiltrated water and recharge underlying fractured bedrock. Interflow soils were divided into deep interflow and shallow-interflow responsive depending if the lateral movement of water was in the deep subsoil or in an E horizon close to the surface. Responsive soils, due to the saturated nature, will saturate quickly after infiltration inducing overland flow. The soil chemical properties for representative profiles of a soilscape were described, characterised and interpreted. Pedological processes were inferred from the soil morphology, chemical properties and water regime measurements in soil profiles. Chemical properties were used to verify if the morphological properties are in phase with the current water regime. Annual duration of saturation (ADs>o.7),which is defined as 70% saturation of porosity was also used to support the chemical property deductions. A conceptual hydrological response model was constructed using soil morphology as an ancient indicator of flow paths, which was improved using chemical properties as recent indicators of the current water regime. The current water regime was verified with real time snapshots of hydrology using hydrometric data.