1. DRAINAGE BASIN [GRADE 12 GEOGRAPHY]

2. THE DRAINAGE BASIN SYSTEM
Drainage Basin: the area drained by a river system or stream network.
Watershed: High ground separating one drainage basin from another.
Stream Network: Individual river channels join together to form a stream network.
Interfluves: The ridges of high ground, i.e. spurs, found between individual channel.

3. DRANAGE BASIN

4. WATERSHED

6. INTERFLUVE
A minor watershed
A watershed within a drainage basin.

7. CONFLUENCE
Where two rivers join

8. TRIBUTARIES
A smaller stream that joins a bigger stream

9. DISTRIBUTARIES
A large river that flows into a number of smaller rivers e.g. at a delta

10. FACTORS PRODUCING INCREASED RUN-OFF
Gradient
Steep
Vegetation
Sparse
Rock type
Impermeable
Soil
Not porous, clayey
Soul moisture
Wet soils
Evaporation rate
Low e.g. overcast
Amount of rainfall
Lots
Types of rainfall
Thunderstorms

11. FACTORS PRODUCING DECREASED RUN-OFF
Gentle
Dense
Permeable
Porous, sandy
Dry
High
Little
Soft soaking rain

12. BASE FLOW

13. WATERTABLE The upper level of the zone of saturation
More or less follows the undulations of the landscape
Where it intersects with the surface, rivers, lakes or oases are formed

14. BASEFLOW

15. GROUNDWATER ZONES

16. GROUNDWATER ZONES

17. GROUNDWATER ZONES (in detail)

18. WATER SUPPLY
Water is one of the most powerful earth carving forces there is.
Run off = precipitation – [surface retention + infiltration + evaporation + evapotranspiration + interception]

19. SHEET/LAMINAR FLOW

20. TURBULENT FLOW

21. RIVER SOURCE
Where a river rises or begins

22. RIVER MOUTH

23. TYPES OF RIVERS
Permanent
Periodic
Episodic
Exotic

24. PERMANENT RIVERS
Always has base flow as even the dry season water table is above the river bed
Found on the south and east coast of South Africa

25. PERIODIC RIVERS Flow only in rainy season
Dry season water table is below the river bed
Found on plateau of South Africa

26. EPISODIC RIVERS Flo only after a heavy rainfall
Wet season water table is also below the river bed
River never enjoys base flow
Found in dry western parts of South Africa

27. EXOTIC RIVERS
Rise in a high rainfall area where there is plentiful run off and base flow
Travel through dry areas where there is very little run off and no base flow
Orange and Nile river

28. OTHER IMPORTANT DEFINITION
Interfluve
Confluence
Water table
Tributaries
Permeable rock
Distributaries
Impermeable rock
River rises
Base flow
River mouth
Through flow
Aquifer
Artesian basin