Demands on the water resources of South Africa are ever increasing owing to population growth
and increased development of urban, peri-urban and rural communities. Problems in terms of
water quantity and quality are likely to be experienced during baseflow recessions. It is therefore
imperative that water resources managers not only understand these baseflow periods of
streamflow, but are able to model them with confidence. Research for this study thus included
a comprehensive literature survey of the factors which affect baseflow as well as the approaches
that previous studies have utilised to analyse and model baseflow recession.
The primary aims of this study were to establish a streamflow database, to construct master
recession curves (MRCs) for each catchment under consideration, evaluate the assumption that
South African rivers recede exponentially, to determine a representative set of catchment
characteristics for use in the baseflow recession analysis, to attempt to explain the MRC trends
using these catchment characteristics and to investigate the feasibility of establishing a rule based
model for baseflow recession.
A streamflow database for South Africa was therefore established. This consisted initially of 202
catchments which were deemed to be recording natural streamflow. MRCs were established for
134 of these catchments. Those MRCs which were established indicate that the majority of South
African rivers do not conform to an exponential model of recession. In order to account for the
trends defined by the MRCs, catchment area, average catchment slope, drainage density, mean
annual precipitation, rainfall concentration, rainfall seasonality, two independent estimates of
groundwater recharge and a geological index were calculated for each catchment. Limited
success was achieved when the data set was divided into subsets in order to group catchments
with similar baseflow recession responses. The geological composition of the catchments
appeared to provide the best results in that those trends exhibited by the MRCs could be explained
by the types and proportions of the lithologies present. Owing to the lack of readily useable
results it was concluded that until further results were forthcoming the development of a rule
based model for baseflow recession analysis in South Africa would be premature. The
establishment of a readily accessible database containing streamflows and associated catchment
characteristics lends itself to future research. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1997.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ukzn/oai:http://researchspace.ukzn.ac.za:10413/5416 |
| Date | January 1997 |
| Creators | Hughes, Gregory Owen. |
| Contributors | Schulze, Roland E. |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
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