Geography
Geomorphology
Drainage Systems in South Africa
- Drainage basin is part of the water cycle = inputs + flow + storage + outputs
- Inputs = precipitation
- Flow = overland in rivers and tributaries or ground water flow
- Storage = lakes and groundwater
- Outputs = river water mouth
- All rivers occur in drainage basins
TERMONOLOGY:
FEATURE DEFINITION
1. River A channeled flow of water.
2. Watershed An area of high land separating 2 or more
drainage basins.
Water flows off a watershed in opposite
directions.
3. Drainage basin The area drained by a main river and its
tributaries.
4. Catchment area The area over which rain falls that is caught
by a drainage basin.
5. River system A main river and all its tributaries.
6. Tributary A river that joins another large river.
7. Interfluve Area of high lying land inside a drainage
basin – often separates tributaries.
8. River mouth Where the river ends as it joins a sea or
lake.
9. Source Where the river begins.
10. Confluence The point where tributaries join the
mainstream or where the 2 rivers join.
11. Overland flow Precipitated water flowing over the surface.
12. Channel flow Surface water that erodes small stream
channels and eventually joins together to
form wider, deeper channels – rivers.
13. Throughflow Water moving through the soil.
14. Permeable rocks Rocks that allow water to seep through
them – aquifers.
15. Groundwater A saturated underground water zone.
16. Water table The upper level of the saturated
underground water zone.
17. Ground water / base flow Water flowing/ moving through the rocks
underground.
, SURFACE RUNOFF, GROUNDWATER AND THE GROUNDWATER TABLE:
GROUNDWATER OCCURS IN 3 ZONES BENEATH THE EARTHS SURFACE:
Infiltration vs Runoff:
Water which enters the drainage system will either infiltrate or become surface runoff due
to the following factors:
FACTOR INFILTRATION RUNOFF
1. Relief Gentle slopes / flat land Steep gradient
2. Soil type Porous Thin, non-porous soils
3. Rock type Permeable aquifers Impermeable rocks
4. Soil moisture Unsaturated, dry soil Saturated, moist soil
5. Vegetation cover Dense vegetation – Little vegetation
interception
6. Rainfall Gentle, soaking rain Heavy thunderstorms
7. Land use Natural / rural areas urban areas – impermeable
surface like tar
8. Evaporation High humidity and low High evaporation
evaporation
Geomorphology
Drainage Systems in South Africa
- Drainage basin is part of the water cycle = inputs + flow + storage + outputs
- Inputs = precipitation
- Flow = overland in rivers and tributaries or ground water flow
- Storage = lakes and groundwater
- Outputs = river water mouth
- All rivers occur in drainage basins
TERMONOLOGY:
FEATURE DEFINITION
1. River A channeled flow of water.
2. Watershed An area of high land separating 2 or more
drainage basins.
Water flows off a watershed in opposite
directions.
3. Drainage basin The area drained by a main river and its
tributaries.
4. Catchment area The area over which rain falls that is caught
by a drainage basin.
5. River system A main river and all its tributaries.
6. Tributary A river that joins another large river.
7. Interfluve Area of high lying land inside a drainage
basin – often separates tributaries.
8. River mouth Where the river ends as it joins a sea or
lake.
9. Source Where the river begins.
10. Confluence The point where tributaries join the
mainstream or where the 2 rivers join.
11. Overland flow Precipitated water flowing over the surface.
12. Channel flow Surface water that erodes small stream
channels and eventually joins together to
form wider, deeper channels – rivers.
13. Throughflow Water moving through the soil.
14. Permeable rocks Rocks that allow water to seep through
them – aquifers.
15. Groundwater A saturated underground water zone.
16. Water table The upper level of the saturated
underground water zone.
17. Ground water / base flow Water flowing/ moving through the rocks
underground.
, SURFACE RUNOFF, GROUNDWATER AND THE GROUNDWATER TABLE:
GROUNDWATER OCCURS IN 3 ZONES BENEATH THE EARTHS SURFACE:
Infiltration vs Runoff:
Water which enters the drainage system will either infiltrate or become surface runoff due
to the following factors:
FACTOR INFILTRATION RUNOFF
1. Relief Gentle slopes / flat land Steep gradient
2. Soil type Porous Thin, non-porous soils
3. Rock type Permeable aquifers Impermeable rocks
4. Soil moisture Unsaturated, dry soil Saturated, moist soil
5. Vegetation cover Dense vegetation – Little vegetation
interception
6. Rainfall Gentle, soaking rain Heavy thunderstorms
7. Land use Natural / rural areas urban areas – impermeable
surface like tar
8. Evaporation High humidity and low High evaporation
evaporation
