1. Today we are learning this content:
5.2 (a, b and c)

2. What is a drainage basin?
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Please watch this a few times!

3. A drainage basin can be defined as the area of land drained by a river and its tributaries.
On a smaller scale (variable from regional to local depending on the size of the drainage basin) the drainage basin is a subsystem within the global hydrological cycle. It is an open system as it has external inputs and outputs that cause the amount of water in the basin to vary over time. These variations can occur at different temporal scales, from short term hourly through to daily, seasonal and annual.
The drainage basin can be of any size, from that of a small stream possibly without tributaries up to a major international river flowing across the borders of several countries.

4. Flows in a Drainage basin Make sure you know all
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Flows in a Drainage basin
Make sure you know all
KEY TERMS in this diagram
You must make a key terms
List!

5. The Drainage Basin Hydrological Cycle Present new information
You must make
Sure you know what
Each key term means
Remember its an
OPEN SYSTEM!
It has INPUTS into the
System and OUTPUTS
Leaving the system
This all happens as part
Of the bigger closed
Hydrological system.

6. The drainage basin cycle
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The drainage basin is a subsystem within the global hydrological cycle. It is an open system with external inputs and outputs that cause the amount of water in the basin to vary over time.
The time taken for these changes to occur can be from hours to years)
A drainage basin is often referred to as the catchment (the area of land drained by a river and its tributaries).
The boundary of the drainable basin is defined by the watershed (the highland which divides and separates water flowing to different rivers).
Drainage basins can be any size, from a small stream to major rivers across international boundaries.

7. Present new information

8. Key processes within a drainage basin and factors that impact upon it
Key processes within a drainage basin and factors that impact upon it. We will covering these in the lesson.
Type of precipitation – Orographic, frontal and convectional
Basin size and shape – look at this briefly but again in a few lessons
Drainage Density – amount of river tributaries/channels
Relief - steepness of the land
Temperature and Climate
Land Use – rural vs urban
Rock Type including permeable vs impermeable rocks and aquifers
Soil Type including the structure of it and texture
Tides and Storms

9. Types of precipitation (Hodder page 7)
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Construct new meaning

10. Factors affecting ‘inputs’
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Precipitation
For precipitation to form it requires the following conditions:
Air cooled to saturation point with a relative humidity of 100%
Condensation nuclei, such as dust particles, to facilitate the growth of droplets in clouds
A temperature below dew point
Rainfall amount
Type of precipitation
Seasonality
Impacts of precipitation on the basin
Distribution within basin
Intensity of precipitation
Variability of rainfall

11. Impacts of precipitation on the drainage basin hydrological cycle
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Complete LL sheet 5.2 a) – use page 8 of the SUG/page 7 and 10 Hodder
Extra info on this slide
Impacts of precipitation on the drainage basin hydrological cycle
The amount of rainfall can have a direct impact on drainage discharge
The type of precipitation e.g. the formation of snow, can act as a temporary store and large fluxes of water can be released into the system after a period of rapid melting resulting from a thaw.
Seasonality. In some climates such as monsoon, Mediterranean or continental seasonal patterns of rainfall or snowfall can have a major impact on the physical processes within the drainage basin
Intensity of precipitation has a major impact on flows on or below the surface. It is difficult for rainfall to infiltrate if rain is intense as soil is saturated and has no capacity.
Variability of rainfall
Secular variability happens long term e.g. result of climate change trends
Periodic variability happens in an annual, seasonal or daily basis
Stochastic variability results from random factors e.g. localised thunderstorms
6. The distribution of precipitation within a basin. This is more noticeable in large river basins e.g. Rhone or Nile which have tributaries that start in different climatic zones.

12. Construct new meaning Physical factors affect the drainage basin cycle
Complete the Heads and Tails
Relief
Has a role in influencing the type and amount of precipitation overall and the amount of evaporation, i.e. the major inputs and outputs. It also has an impact of the vegetation type.
Climate
Determines the amount of infiltration and throughflow and, indirectly, the type of vegetation
Vegetation
Can impact on the subsurface processes such as percolation and groundwater flow (and, therefore, on aquifers). Indirectly, it can alter soil formation
Geology
Can impact on the amount of precipitation. Slopes can affect the amount of runoff
Soils
The presence or absence of this can have a major impact on the amount of interception, infiltration and occurrence of overland flow, as well as transpiration rates.
Construct new meaning

14. Rocks types
Construct new meaning

15. Basin Size Construct new meaning
Drainage density is the total length of all the streams and rivers in a drainage basin divided by the total area of the drainage basin. It is a measure of how well or how poorly a watershed is drained by stream channels.
Basin Size

16. Soil Types
Construct new meaning

17. Complete LL sheet 5.2 b) – use Hodder page 11 and the SUG page 10.
Use the sheet and the Hodder text book to answer the 12 mark response at the bottom of the page. (This is homework)

18. Present new information

19. Present new information
There are lots of ways in which people can disrupt the water and drainage basin cycles.
For example:
Farming and irrigation
Deforestation
Abstraction
Construction of dams
Building river defences
Overpopulation
Pollution from industry
Pollution from fertilisers
Global warming
Urbanisation

20. The Hydrological Cycle
Review
Useful link and summary clip:
NASA:
Now complete LL sheet 5.2c)
Use the sheet to write a model response for the 8 mark question.