RHP South African
River Health Programme
State of the Rivers Report
Crocodile, Sabie-Sand & Olifants
River Systems
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Sabie-Sand River System Crocodile River System Sabie-Sand River System Olifants River System summary ecoregion 4.04 in Sabie-Sand Catchment

The Sabie-Sand River System

Ecoregion 4.03

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.

Present Ecological State

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.

Ecoregion 4.03

The Importance of Riparian Vegetation

Desired Ecological State and Response by Resource Managers

The headwaters of the Sabie River are important wetland areas that regulate water flow and quality. These areas provide habitat for many species of animals and plant. For this reason, a natural health state should ideally be maintained. However, in view of the extensive forestry activities and occurrence of alien vegetation and trout, a good state is recommended as a more pragmatic goal.

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