Abstract
M.Sc.
The water quality monitoring project undertaken on the Blyde River in Pilgrim's Rest and
surrounding area, provided information on various parameters. These included the macro
variables (pH, temperature, conductivity, dissolved oxygen concentration, oxygen saturation
percentage and turbidity), micro variables (ionic and metal concentrations) and
fauna (fish and invertebrates). Field and experimental data were integrated to form a realistic and
representative picture of the general state of health of the Blyde River.
The macro variables (pH, temperature, conductivity, dissolved oxygen concentration, oxygen
saturation percentage and turbidity) were all within the guideline limits as provided by the
Department of Water Affairs and Forestry. The ionic concentrations (calcium, magnesium,
sodium, chloride and nitrate) were acceptable and conformed to guideline values.
The aquatic macro-invertebrate and habitat quality survey indicated that most of the sampling
sites could be described as good. Sampling site 2 (next to reduction works) was classified as
poor. This is the result of mining activity at this specific site situated at the rock dump at Peach
Tree Creek. The extensive disturbance of the habitat is the result of 130 years of mining
activities.
The metal concentrations in the Blyde River exceeded the guideline limits, except for manganese.
Aluminium toxicity is pH dependent, and increases with a decrease in the pH. The alkaline pH in
the Blyde River acts as a buffer against the aluminium toxicity. The lead concentration in the
Blyde River exceeded the Department of Water Affairs and Forestry guideline limit. Lead is
hazardous to most forms of life. Zinc is toxic to fish and aquatic organisms at relatively low
concentrations. Although nickel is a natural element of the earth and water, mining activities
cause nickel emissions and an increase in the nickel concentrations in water systems. Copper is
regarded as a highly toxic metal if present in high concentrations. Iron is not easily absorbed by
aquatic organisms and because of its limited toxicity and bioavailability, described as a noncritical
element. Chromium is biologically inert.
Despite of a lack of information on the concentrations of metals in the Blyde River before the
onset of mining activities at Pilgrim's Rest, it is clear that the extensive disturbance of the habitat
at Peach Tree Creek and Vaalhoek, and to a lesser extent at Delvers' Creek exists. Present and past mining activities in the Pilgrim's Rest area resulted in the deterioration of the water quality
in the Blyde River. Rehabilitation of the area around the rock dump at Peach Tree Creek will
have to be done to prevent seepage from the rock dump and disturbed area to the river. Measures,
such as the construction of paddocks and berm walls to collect seepage before it reaches the river,
will have to be implemented. The water will then have to be treated before releasing it into the
river.
The acute, sub-lethal toxicity tests with nickel and lead were conducted based on the
concentrations as derived from water samples taken from the Blyde River, during the monitoring
phase of the project. The results of the blood physiological experimentation indicated that normal
physiological functioning were disturbed when fish were exposed to sub-lethal concentrations of
lead and nickel. Results indicated that stimulation of the immune system, osmotic stress and
hypoxic conditions arise after lead and nickel exposure. Hypoxia arises because of a deficiency
in the amount of oxygen reaching bodily tissues. Osmotic stress is a result of affected gill and
kidney functioning. The metabolic variables indicated that the metabolism of trout was affected,
because of stress associated with metal exposure. The nervous system functioning was also,
affected, as derived from the enzymatic variables. Taking these factors into consideration, the
normal functioning and survival of rainbow trout (Oncorhynchus mykiss) is hindered.
The acute, lethal toxicity tests of nickel on rainbow trout (Oncorhynchus mykiss) and chubby
head barb (Barbus anoplus) were performed using nickel concentrations as determined in the
Blyde River. The 100% mortalities recorded, when exposing the fish to these concentrations,
indicated that the Blyde River provides a buffer action against the toxic effect of nickel on the
aquatic organisms. Should this buffer action be disturbed, for instance a sudden drop in water
pH, the toxicity of nickel will increase and have detrimental effects on the aquatic organisms.
Further deterioration of the water quality in the Blyde River should be avoided at all cost. Large
scale yellow fish (Barbus marequensis) were only found at sites below sampling site no 8, which
is alarming and a further confirmation of habitat degradation.
To prevent further degradation of the water quality in the Blyde River annual biomonitoring in
conjunction with experimental studies are suggested to obtain information, which enables
effective managerial decision making. Measurements should be taken to reduce the impacts of
mining and agricultural activities, if future studies indicate further water quality degradation. Objectives regarding the health of the aquatic environment should be set and actions taken to
prevent the impactors from doing further harm.
The Pilgrim's Rest area can be developed for Eco-tourism, and therefore the aim should be to
create awareness of the river and its surroundings and involve people in the conservation thereof.