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Evaluation of macro-invertebrates as bio-indicators of water quality and the assessment of the impact of the Klein Plaas dam on the Eerste RiverBredenhand, Emile 12 1900 (has links)
Thesis (MScAgric (Conservation Ecology and Entomology)--University of Stellenbosch, 2005. / A semi-arid country, like South Africa, with unpredictable seasonal rainfall, is subject
to great scarcity in water and an ever-increasing demand from the rising human
population. Therefore, efficient reservoirs as well as monitoring methods are needed
to manage the South African water supply.
This study was undertaken on the Eerste River in the Western Cape, South Africa,
focusing on the impact of the Klein Plaas dam system on the benthic
macroinvertebrates. The study also examined the use of benthic macroinvertebrates
as bioindicators of water quality with special reference to the South African Scoring
System Version 5(SASS5) that is currently being used nationally.
The impoundment of the water, as well as the inter-basin transfer programme and the
experimental cage-culture trout farm, all play a significant role in the disturbance
impact of the dam on the Eerste River system. The disturbance is manifested as a
drop in water quality that can be seen in the distribution of keystone species, changes
in the riparian vegetation, as well as in physical-, chemical-, and biomonitoring
evaluations.
The study also indicated that the SASS5 is effective, but needs some adjustments,
such as inclusion of a prediction phase, finer spatial-scale methodologies and greater
consideration of the rarity of species.
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An ecological assessment of the Holsloot River, Western Cape, South AfricaLe Roux, Anso 02 1900 (has links)
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)
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