In South Africa many watercourses are dry for much of the year and tend to be under-valued. However, even the smallest watercourses have great ecological value, not least because they ultimately feed into streams and rivers (which are simply larger watercourses). It’s easy to spot dry watercourses as the vegetation will be taller and denser than that of the surrounding area. This is because there is more available groundwater along watercourses.
The riparian (river edge) vegetation and the underground water makes watercourses ecologically valuable to many animals. Trees and shrubs provide food, shelter and nesting sites. Since watercourses cross relatively long distances they connect different components of an ecosystem. These corridors are important to animals that need to use different habitats at different times of the year. It’s therefore important not to break the continuity of a watercourse.
Where watercourses cross relatively level ground, they usually have floodplains beyond the banks of the actual channel. The floodplains are sensitive to over-exploitation and need to be conserved or carefully managed as they play an important role providing fertile areas and good grazing.
- Do not grade, deepen or fill watercourses.
- Avoid excessive abstraction (use) of groundwater from watercourses. Optimise water use by implementing best practices such as drip irrigation. If possible, store water in the rainy season to reduce the need for pumping water in the dry season.
- Do not create permanent structures below one-in-50-year flood lines and as few as possible below one-in-100-year flood lines.
- Do not store hazardous materials, including chemicals, fertilisers and fuel, near watercourses or on floodplains. And don’t create waste dumps within watercourses or on floodplains.
- Provide special protection for all wetlands and reed beds on floodplains, because these will help to slow down run-off water during flash floods, reducing damage.
- Do not allow waste, fertilisers and silt to run directly into watercourses.
- Set aside an undisturbed buffer zone on both sides of watercourse channels. This should be at least 30m wide, preferably 50m or more. These zones help to protect watercourses against polluted run-off, and provide enough space for the development of riparian vegetation.
- If you wish to rehabilitate or modify a water course, consult the Mondi Wetlands Trust for advice.
Benefits to you
- Improved water quality downstream and in dams.
- Good relations with downstream neighbours.
- Recharged groundwater.
- Protection against erosion and flash floods.
The importance of vegetation
Allow natural, indigenous vegetation to grow up on the banks of watercourses, as the health of rivers and streams is largely dependent on the condition of the riparian vegetation. This stabilises the banks, filters incoming run-off, shades the water and keeps it cool, and provides the right kind of organic nutrients, mainly in the form of leaf litter, to sustain aquatic life.
Eradicate alien vegetation from watercourses. Alien species tend to flourish in these areas and prevent the growth of indigenous species. Dense stands can dry up watercourses and create an environment inhospitable to both plants and animals.
Source: Harrison, J. & Young, D. 2010. Farming for the Future: Farming Sustainably with Nature. Animal Demography Unit, University of Cape Town. Contact the Mondi Wetlands Trust on www.wetland.org.za