Natural sciences
The earth and beyond
Rivers and their catchment areas
Educator section
Memorandum
Assignment 10:
1. Assignment clear in module. Assignment can lead to an exhibition of collected samples, photos and notebooks.
Follow-up visit for cleaning up is recommended.
Assignment 11:
Listen at least to Wendy Oldfield's song "Acid Rain". Learners take the lead and answer the following question:
"Which environmental issues are addressed and what solutions do we have for the problems?"
Assignment 12:
Help the learners with a framework, e.g.
- The river as an environment wherein plants and animals can live
- light
- visibility
- oxygen
- no poison
- protection against temperature changes
- Life in a river (above-mentioned environment)
- types of plants
- types of animals
- mutual dependence of plants and animals
Leaner section
Content
Activity: to discuss the role of rivers in nature [lo 1.1, lo 1.2]
IN THE LEARNING UNIT DEALING WITH FOSSILS WE SAW THAT THE DRY KAROO USED TO BE A MARSHLAND THAT COVERED APPROXIMATELY THREE-QUARTERS OF THE SURFACE AREA OF SOUTH AFRICA. IT IS CLEAR THAT FRESH WATER HAS PLAYED AN IMPORTANT ROLE IN THE LIVES OF PLANTS AND ANIMALS AS WELL AS PEOPLE FOR MILLIONS OF YEARS.
A RIVER IS MORE THAN WATER!
- Rain absorbs carbon dioxide and oxygen when it travels through the atmosphere. While it travels down a mountain slope, tiny plant particles from the vegetation are also caught up in it. In this way water takes up sufficient soluble nutrients to sustain animals that live in water, as well as plants.
- Rivers are generally endangered. The fact that people need water for survival, places a great deal of pressure on rivers to meet this need and to carry away waste material.
- Rivers are not drainage conduits for the removal of waste: they are complex systems.
- Different plants and animals exist along the different reaches of a river. These organisms utilise the natural materials contained in the river in the natural process of their lives. This ensures that the water in the river is purified continually. Rivers are also able to absorb much pollution.
- This unique characteristic of rivers is largely destroyed by excessive pollution, damming up of water and canalisation.
- The Department of Water Affairs and Forestry acknowledges that rivers are living systems that should be conserved. Healthy rivers are attractive features that provide us with water and make it possible to save money. The capacity for self-purification that is observed in rivers can make it possible to save thousands of rand that would have to be spent on building purification projects, provided that we protect this capacity.
- Rivers need people to protect their interests and to fight for them.
River catchment areas
- The catchment area of a river, is the area between the mountain peaks where the river has its source and the coast where the river mouth is. The area that is drained by a single river forms its catchment area.
- The characteristic feature of any river is determined by the activities (human and natural) that take place in the catchment area. All the water that is precipitated as snow, dew, mist and rain in any particular catchment area flows together in a river. Only a very small quantity of this water is lost through evaporation.
