Ecoregion and River Characteristics

This ecoregion covers the upper section of the Drakensberg Escarpment, with altitudes between
1 000 and 2 000 m above mean sea level, and high mountainous relief. As a consequence of the range in altitude and relief, there is a large variation in rainfall (600-1 200 mm per year) and mean annual temperature (10-18°C). The dominant vegetation is a combination of mountain grassland (on the upland areas) and afromontane forest (in gorges and lower slopes). These overlie shallow lithosols and well-developed, sometimes leached, mature soils, respectively. The main geological types are quartzites, shales, basalts, andesites, conglomerates, irons, granites and gneiss.

The headwaters of the Sabie River and its tributaries (the Sand, Marite, Mutlumuvi, Motitsi and Mac Mac Rivers) arise in the upper parts of the escarpment. These rivers are cold mountain streams, narrow with moderate to steep gradients, and hence fast flowing. Waterfalls are common, and rocky pools and rapids abound.

Overall good. Invertebrates indicate that the water quality is very good, although the fish populations are somewhat impaired, reflecting a fair to poor state. Some natural riparian forests occur in the upper parts. In general, the ecological state is better in the upper reaches of this ecoregion with increasing degradation further downstream.

Drivers of Ecological Change (Land-use activities)

Forestry activities close to or within the riparian zone are the primary threat to health of the riparian habitats and vegetation. Lack of ground cover underneath the trees causes instability and erosion of soils. If close to the waters edge, this can cause massive destabilisation of the banks, and erosion. Alien vegetation uses more water than indigenous vegetation and is also a threat to natural vegetation and may reduce biodiversity in the riparian zone.

Trout is a threat to in-stream ecological health, through diversion of water for dams and weirs, which impact on the water flows in the area. Trout also preys on, and competes with, indigenous fish species, changing the composition of fish populations, and rivers may become enriched with nutrients from fish feed and waste.