The Umzimvubu catchment on the eastern coastal escarpment of South Africa is sensitive to
anthropogenic influences,with commercial and subsistence agriculture, irrigation, domestic and rural
settlements and forestry compete for water use. An adequate supply of water to the region is seen
as imperative in the light of the recent establishment of forest cultivation. In order to provide a sound
assessment of the impacts of afforestation on the catchment, the subsurface hydrological processes
of hillslopes on the Molteno sedimentary formations of the region must be clearly understood. Since
the runoff hydrograph is, to a large degree, dependent on the subsurface processes, a number of
models that simulate small catchment runoff have been developed. However, recent successful
application of tracer techniques to hydrological modelling has shown that the subsurface processes
are still not fully understood (Schultz, 1999), and whether or not the subsurface processes are
modelled adequately is most often not verified, since there is a lack of relevant data. It is, therefore
imperative that the subsurface component of these small catchment runoff models be improved. This
can be achieved by first observing detailed subsurface water dynamics and assessing these against the
catchment runoff response.
In this dissertation, results from a detailed experiment that was initiated in a 1.5 km2 catchment in
the northern East Cape Province are shown. Nests of automated tensiometers, groundwater level
recorders and weather stations have been placed at critical points around the catchment, and these ,
together with soil hydraulic and physical characteristics are used to define and identify the dominant
hillslope processes. Two crump weirs record runoff from these hillslopes.
The results of this subsurface study highlight the dynamics of surface and subsurface water in the
hillslope transects. It is evident that the subsurface processes are strongly influenced by the -bedrock
topography as well as the soil characteristics, such as macropore flow and deep percolation. Using
the monitored data and 2-D vadose zone modelling, the dominant hillslope processes have been
defined and are used to aid in the selection of critical parameters to be used in estimating the
catchment runoff. Results show that a clear understanding of the subsurface dynamics can lead to a
realistic estimation of catchment scale runoff response. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2000.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ukzn/oai:http://researchspace.ukzn.ac.za:10413/4936 |
| Date | January 2000 |
| Creators | Hickson, Rory Macready. |
| Contributors | Lorentz, Simon A. |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
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