Human related activities have influenced the rivers of the southern Western Cape since
as early as the 1700’s. As there is no detailed information available on ecological status
of the Holsloot River, a tributary of the Breede River, this study aimed to gain insight into
the effect of impacts associated with human activities on the habitat integrity of this river.
The study intended to understand how seasonal changes, catchment characteristics
and events are reflected in the ecological status of habitats along the river by applying
bio-monitoring and river health measurements at selected sites in the upper, middle and
lower reaches of the Holsloot River and compare the results to that of an undisturbed
reference site. Results obtained in this study are compared with data gathered in
2008/2009 to determine if the ecological status of the river had changed in the period
between the two sampling times. The study included assessment of the ecological
status of the river based on standard bio-monitoring protocol (SASS5, IHI, IHAS and
VEGRAI) as well as in situ water quality analysis (pH, dissolved oxygen, electrical
conductivity and total dissolved solids).
The construction of the instream Stettynskloof Dam changed the configuration of the
riparian zone and river channel in the upper catchment area. Agricultural- and other
human related activities, with consequent water abstraction, non-point-source pollution,
loss of riparian vegetation, as well as dense stands of alien invader plants influence flow
patterns and affects river ecology, especially in the dry summer months. Providing
sufficient stream flow and adequate water levels, human related activities can create a
larger variety of habitat types available that can support larger biodiversity and higher
productivity. The level of inundation and stream flow, influenced by water abstraction as
well as irrigation return-flow from extensive drainage systems especially in the dry
months, contribute to the loss of biodiversity in the middle and lower reaches of the
river. Where the upper reaches of the river are largely natural with few modifications, the
habitat integrity deteriorates in the middle reaches so much so that ecosystem
functioning are collectively impaired in lower reaches due to human related impacts.
Sensitive macro-invertebrates found at lower seriously impacted parts of the river
however, were in all probability washed down from lower impacted upstream habitats
and may expectedly be able to again occupy habitats downstream if water quality and
habitat availability improves. / Environmental Sciences / M. Sc. (Environmental Science)
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:unisa/oai:uir.unisa.ac.za:10500/10194 |
| Date | 02 1900 |
| Creators | Le Roux, Anso |
| Contributors | Brand, M. E. (Bokkie), Brown, Leslie R. |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Format | 1 online resource (xvii, 208 leaves) : color illustrations, color maps, color graphs, application/pdf |
| Rights | University of South Africa |
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