Abstract
The Nyl River floodplain is one of the jewels in the arid Limpopo Province. The
conservation and protection thereof is thus vitally important. The Nyl River
Floodplain is an ephemeral floodplain and the largest of its type in South Africa.
The wetland is a Ramsar site and provides habitat for a number of endangered
species of birds and animals. The aims of this project were to (1) assess the
water and sediment quality in the Nyl River system, (2) to determine baseline
levels of pollution, (3) to develop a rapid wetland assessment protocol for
biomonitoring and (4) to provide a framework for wetland management.
Eighteen sites in the Groot Nyl and Klein Nyl rivers, as well as in some of the
larger tributaries were selected. Water and sediment were sampled and analyzed
to determine metal and nutrient levels. Bacterial analysis also took place at five
of the sites along the course of the system. The results obtained from the water
analysis indicate that bacterial levels in the system are cause for concern.
Although metal levels in the water and the sediment are higher than Target
Water Quality and Sediment Guideline Ranges, the metal levels remained
relatively constant throughout the system. The metal levels indicated that they
pose no potential threat to the system. The comparison between the present and
historical ecological state indicated that nutrient levels are increasing in the
system. The levels of toxic ammonia did not increase and thus the water quality
in the system can thus be classified as fair.
The sequential extraction of the sediment indicated that the majority of the metals
in the sediment are not readily bioavailable. They were released by the fourth
and fifth fractions and will only become available in the presence of strong
reducing or oxidizing agents. Organic contaminant levels were also analysed in
the sediment. The results indicated traces of PCB’s (Poly-chlorinated Biphenyls)
and pyrethroids (Cypermethrin), but concentrations were too low to quantify.
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The third aim of the project was to develop a Wetland Assessment Protocol. A
draft version of the protocol was developed using a modified version of the South
African Scoring System version 5 (SASS5). Due to the lack of biotopes in the
system, the vegetation biotope was chose as sampling habitat. Aquatic
invertebrates were collected and a total score was given to each sampling site.
The total site rating was determined using a combination of the SASS5 scoring
system, a newly developed habitat assessment system and a human impact
assessment system, The Wetland assessment protocol identified changes in
water quality, but more refinement is required on a system with a greater
pollution gradient.
The fourth aim of the project was to set up a draft framework for wetland
management. The framework is based on the National Estuary Programme of
the USEPA. It has been interpreted and adapted for use in wetlands, in a similar
way to which USEPA ecological risk assessment guidelines have been adapted
for the South African scenario.
This research project was thus able to (1) provide baseline values for the Nyl
River System, (2) to produce a first draft of a Wetland Assessment Protocol and
(3) provide a framework for wetland management. It is envisaged that the
information in this thesis will provide useful information in the protection and
management of the Nyl River.
Prof. J.H.J. Van Vuren