Hillslope experiments in the north east Cape region to measure and model subsurface flow processes.
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Date
1997
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Abstract
Several hydrological studies claim that available water resources in a catchment are affected
by large scale afforestation, especially where the regional rainfall is considered marginal for
the support of silviculture. Nevertheless, the mechanisms and magnitude of the
perturbations to the receiving water resources due to afforestation are still not clearly
understood. To improve this understanding an intensive hydrological experiment has been
initiated in the small grassed Weatherly catchment of the Mondi, North East Cape Forests.
Details of the soil water dynamics on the Molteno formations in the catchment have been
be studied.
This research presents a description and first results of the establishment of an experiment
which comprises monitoring the water budget of the grassed catchment prior to the
afforestation of the catchment to plantations of exotic trees. The studies currently include,
monitoring the infiltration and redistribution of soil water on a hillslope as well as
monitoring of interflow mechanisms and localised mechanisms of soil water accumulation
influenced by the topography and geology of the catchment. In addition to the intensive soil
water monitoring, specific experimentation has been conducted at various locations on the
hillslope. These comprise macropore flow process studies and 2-dimensional tracer
experiments. Details of these experiments as well as the automated soil water and
groundwater monitoring instrumentation are presented. An intensive soil survey on a 30 m
x 30 m grid as well as a comprehensive measurement strategy of soil physical and hydraulic
properties are highlighted. A review of 2-dimensional numerical hillslope soil water process
models is also presented.
Results from this research show that on hillslopes underlain by Molteno sandstones localised
perched water tables form. These water bodies, upon reaching a critical height above the
bedrock cascade downslope as interflow recharging the water bodies downslope. The
response to infiltration increases downslope and in the toe region interflow occurs readily
in response to rainfall compared to the midslope where substantial rain needs to infiltrate.
Description
Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1997.
Keywords
Groundwater flow., Groundwater--Cape., Groundwater--Mathematical models., Slopes (Physical geography)., Theses--Bioresources Engineering and Environmental Hydrology.