Rivers and Catchments
There are four main perennial rivers that have their source in the Great Escarpment region of the Biosphere: the Selati, Makutswi, Blyde and Sand Rivers. These join the Olifants (except for the Sand) and form the Lower Olifants Catchment Basin flowing into Mozambique through the Kruger National Park (the Komati Catchment in the case of the Sand).
Main catchment systems of the Kruger National Park
Each of these rivers has numerous perennial and non-perennial tributaries flowing into them. Not only is the escarpment area an important catchment, but all the rivers are a lifeline to the drier savannah regions. These rivers are an important source of water to rural communities, agriculture, mining, domestic use in towns, wild animals, recreational activities and they also create habitats for a diverse range of other aquatic organisms.
Greater Limpopo ecosystem showing perennial rivers of the Olifants and Komati catchments
Each of the eleven perennial rivers that flow through the Biosphere Reserve has some degree of conservation status. At some stage, most of the rivers flow through a protected area for at least part of the way. However, because water is one of the most precious resources, these rivers are insufficiently protected. There are projects such as the Olifants River Forum which help to create awareness and nurture a caring and responsible attitude amongst the communities and industries depending on the water of the Olifants River. The core areas of the Biosphere Reserve certainly contribute towards the conservation of these valuable systems, but unfortunately greater efforts are required.
The Blyde River is a major contributor to the Olifants River in terms of volume and quality of water. In fact many ecologists feel that if it were not for the Blyde River little or no water would reach Mozambique via the Olifants River in times of drought. The Blyde River is classified as one of the few 'A' rivers in the country, which means that it is considered to be close to a 'pristine' river. It also contributes 65% of the fish diversity in the Biosphere Reserve.
An initiative to have the Blyde River declared an International RAMSAR Site (recognising critical to the 1971 Convention on Wetlands) by UNESCO is presently underway.
The Blyde River, with its Afromontane setting and unique biodiversity, is presently the subject of a RAMSAR application
The riparian forest along the Blyde River, above its confluence with the Olifants River, is probably the most extensive natural riparian forest of its kind in South Africa and is of considerable conservation value.
This riparian forest is classified as Lowveld Riparian Forest and forms part of one of the smallest forest types within South Africa. Comparable riparian forests over much of its distribution within the eastern half of South Africa are mostly fragmented or transformed by alien plant invasions.
The forest along the Blyde River is extensively developed within the last few kilometres above its confluence with the Olifants River. This fragile area is only around 100 Hectares in extent. The Lowveld Riparian Forest creates an important habitat and refuge for specialised fauna and flora such as the Vulnerable Pelís Fishing Owl whose habitat in South Africa is dwindling rapidly.
This Blyde River section which exclusively contains the Lowveld Riparian Forest is also an important refuge area for several fish species and several other animals which have largely disappeared from the Olifants River due loss of habitat.
Large or poorly planned development initiatives in the forested areas can eliminate the wilderness effect of this unique area by fragmenting the riparian zones and reducing available habitat. This type of disturbance will also decrease or displace the faunal component and will increase the spread of alien invasive plants.
Poorly planned development can further destabilise the riverbanks, which are already under stress due to the loss of sediments in the system as a result of the releases of sharp peaked and silt free floods from Swadini Dam. The destabilisation of this river can also pose a danger to human lives and will have a negative impact on the capacity of this area to function as a refuge.
All development in the area should take cognizance of this valuable asset in terms of biodiversity and conservation of our natural heritage, and any development should be directed towards utilizing this area without destroying the aspects which makes this area unique.
These concerns have led to the establishment of the Blyde-Olifants Conservancy, a forward thinking attempt to protect this scarce natural resource for future generations.
The Olifants River (Rio dos Elefantes) drains a catchment area of 54,575 square kilometres, making it the biggest river flowing through the Kruger National Park. Although abstraction for irrigation and other uses, as well as changes in the catchment characteristics, have decreased the runoff from the catchment, this river has only twice stopped flowing.
A large proportion of the two-and-half million people living in the Olifants catchment lives in rural third-world conditions, being concentrated mainly in settlements with limited infrastructure. Improvements in their living standards and increased urbanization will have a dramatic impact on the water requirements for domestic use.
There are 30 major dams in the basin. Most of these are used mainly for primary water supply or for irrigation purposes. The decrease in runoff caused by afforestation is limited and restricted primarily to the Blyde River sub-catchment.
Mining activities and power stations are scattered across the basin. The concentration of industrial development, power-stations, rapid urbanisation, irrigation activities, soil erosion mainly due to overgrazing and runoff from rural towns and villages of the Olifants River, all cause serious deterioration in water quality.
Mining and industrial activities at Phalaborwa, just outside the western border of the Kruger National Park (KNP), are also a major source of pollution. Extremely low flows aggravate water quality problems and cause certain aquatic habitats to disappear. High salinity, pollution by heavy metals and high silt loads are the main concerns for conservation and have contributed to the disappearance of at least 5 fish species from the Olifants River (Deacon, 1994).
The high silt loads are generated when sediment-laden releases from the Phalaborwa Barrage are made and have been the cause of massive fish kills downstream in the KNP.
Through the involvement of the Water Quality Management Division of the Department of Water Affairs and Forestry, a system of management rules evolved in the Phalaborwa vicinity to address the water quality problems. These include the re-circulation of seepage water to the source industries, the establishment of purification plants, and the redirection of polluted water from the Selati River (a tributary) into the Phalaborwa Barrage to achieve maximum dilution. In spite of these measures the water is often still so polluted that the KNP has to resort to boreholes for potable water use at Olifants and Satara rest camps.
The problem of water pollution in the Olifants River from the Phalaborwa mines and industries is a crucial one, which is being addressed at several forums at present. Appropriate management actions are continuously identified and implemented to achieve the end goal of rehabilitation of the Olifants River.
The Sabie River (with a catchment of 7,096 square kilometres) is the only river in the Kruger National Park that has never stopped flowing. Furthermore, the water of the Sabie River is still of excellent quality, these factors being reflected in the high biodiversity which still occurs alongs its range. In this regard the Sabie River provides an excellent example of a river that has been utilised for purposes other than nature conservation without serious effects to its ecology.
In spite of the effects of gold mining, intensive irrigation farming covering almost ten thousand hectares, forestry (82,000 ha), much cattle farming and high-density rural populations in its catchment, it still remains a biologically rich river. It is considered to be the river that is the least affected by activities outside the Park.
During recent years however, the flow became very low and the resultant drop in the general water table in the primary channel of the river led to tree mortalities in various reaches of the river. During the exceptionally dry period experienced during the 1991/92 and 1994/95 rainy seasons, flows of as little as a tenth of a cubic metre per second occurred in the eastern part of the river. This phenomenon is related to a combination of factors, namely, the exceptionally low rainfall experienced during these years, the presence of commercial irrigation farming, and the increase of informal, uncontrolled irrigation from the river and the occurrence of very large areas of exotic forests in the upper catchment areas.
As the pressure on the Sabie River increases, it can be expected that more storage dams in the upper catchment will be considered. Development is regulated and the forestry sector continues to clear wetlands of exotic trees in the upper catchment.