Drainage Systems in South Africa
Terminology 2
Drainage Systems in SA 3
River systems 3
Drainage basin & catchment area 3
What happens to precipitation that falls in drainage basin 3
Features of Drainage Basin 4
Important watersheds in SA 4
Surface runoff & groundwater 5
Factors determine how much water enters drainage basin will become surface runoff & how much
will infiltrate underground 5
Relief 5
Soil type 5
Rock type 5
Soil moisture 5
Vegetation 6
Rainfall 6
Land use 6
Water table 6
Types of rivers 7
Permanent rivers (perennial) 7
Exotic rivers (perennial) 7
Periodic rivers (non-perennial) 8
Episodic rivers (non-perennial) 8
Drainage patterns 9
What is a drainage pattern 9
Patterns depend on geology / topography of area in which they are found 9
Radial 9
Trellis 9
Rectangular 10
Centripetal 10
Patterns that develop independently of the rock structure / gradient 10
Dendritic 10
, Deranged 11
Parallel 11
Drainage density 12
Formula 12
Factors influence drainage density 12
High evaporation rates 12
Regions with high rainfall 12
Large amount infiltration 12
Hardness of rock in basin 12
Discharge of a river 13
What does discharge of river depend on 13
What influences the way in which water flows 13
Laminar flow 13
Turbulent flow 13
Factors influencing laminar & turbulent flow 14
River’s load 14
Flow speed 14
Narrow channel 14
Deep channel 14
Wide, level channel 14
Flow speeds in river channel 15
1
, Terminology
Catchment area
Drainage area supplies water to a river. Interfluves
This water comes from rainwater and Ridges of high ground between
flows down the slope as well as from individual channels
underground water, which seeps into
the river. Overland flow
Rainwater flowing over the surface
Drainage basin
The area drained by a river system Channel flow
Water flowing in a river channel
Source
The place where a river begins Throughflow
Water flowing through the soil
Mouth
Where the river flows into a sea or lake Permeable rocks
Rocks that allow water to seep in
Surface runoff
Rainwater flowing over the surface Impermeable rocks
Rock without pore spaces / cracks
Watershed through which water is able to pass
High ground separates one drainage
basin from the adjacent drainage basin Groundwater
Underground water
Stream / river network
Individual streams & rivers that are Groundwater flow
connected Water flowing through underground
rocks
Tributaries
Individual river channels forming the Water table
stream network Upper surface of groundwater
Confluence Base flow
Point where one river in network joins Groundwater that seeps into a river
another
2
Terminology 2
Drainage Systems in SA 3
River systems 3
Drainage basin & catchment area 3
What happens to precipitation that falls in drainage basin 3
Features of Drainage Basin 4
Important watersheds in SA 4
Surface runoff & groundwater 5
Factors determine how much water enters drainage basin will become surface runoff & how much
will infiltrate underground 5
Relief 5
Soil type 5
Rock type 5
Soil moisture 5
Vegetation 6
Rainfall 6
Land use 6
Water table 6
Types of rivers 7
Permanent rivers (perennial) 7
Exotic rivers (perennial) 7
Periodic rivers (non-perennial) 8
Episodic rivers (non-perennial) 8
Drainage patterns 9
What is a drainage pattern 9
Patterns depend on geology / topography of area in which they are found 9
Radial 9
Trellis 9
Rectangular 10
Centripetal 10
Patterns that develop independently of the rock structure / gradient 10
Dendritic 10
, Deranged 11
Parallel 11
Drainage density 12
Formula 12
Factors influence drainage density 12
High evaporation rates 12
Regions with high rainfall 12
Large amount infiltration 12
Hardness of rock in basin 12
Discharge of a river 13
What does discharge of river depend on 13
What influences the way in which water flows 13
Laminar flow 13
Turbulent flow 13
Factors influencing laminar & turbulent flow 14
River’s load 14
Flow speed 14
Narrow channel 14
Deep channel 14
Wide, level channel 14
Flow speeds in river channel 15
1
, Terminology
Catchment area
Drainage area supplies water to a river. Interfluves
This water comes from rainwater and Ridges of high ground between
flows down the slope as well as from individual channels
underground water, which seeps into
the river. Overland flow
Rainwater flowing over the surface
Drainage basin
The area drained by a river system Channel flow
Water flowing in a river channel
Source
The place where a river begins Throughflow
Water flowing through the soil
Mouth
Where the river flows into a sea or lake Permeable rocks
Rocks that allow water to seep in
Surface runoff
Rainwater flowing over the surface Impermeable rocks
Rock without pore spaces / cracks
Watershed through which water is able to pass
High ground separates one drainage
basin from the adjacent drainage basin Groundwater
Underground water
Stream / river network
Individual streams & rivers that are Groundwater flow
connected Water flowing through underground
rocks
Tributaries
Individual river channels forming the Water table
stream network Upper surface of groundwater
Confluence Base flow
Point where one river in network joins Groundwater that seeps into a river
another
2
