1. 2. The Operation of the Drainage Basin as an ‘open system’
Aims: Make sure you know what a drainage basin looks like. Its important you understand ALL the key terms. You most know the draiange basin cycle as a hydrological system, its inputs/outputs, flows, transfers and physical influences.

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

3. What is a drainage basin?
Present new information
Please watch this a few times!

4. Prepare for learning
Using the diagram of the drainage basin hydrological cycle to help you; complete the flow diagram by filling in the missing boxes

5. Prepare for learning
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 – ADD THESE NOTES TO TOP OF FLOW DIAGRAM

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

7. 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.

8. The drainage basin cycle
Present new information
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.

9. Present new information

10. Review
Present new information
A Recap of rivers at GCSE?!
Or try and complete if its new to you in your pair
Spend 3 minutes completing the sheet showing the key features of a drainage basin

11. Present new information

12. Flood Plain Stream Channel Groundwater Store Present new information
Features of a
Drainage Basin
Remember key terms
& definitions are
vital and its an open
System!
Stream Channel
Add labels to this diagram
Groundwater Store

13. A Drainage Basin
Present new information

14. Key processes within a drainage basin and factors that impact upon it
Key processes within a drainage basin and factors that impact upon it. Discuss……and add notes against diagrams
Type of precipitation – Orographic, frontal and convectional
Make notes on this – page 7 hodder or Oxford page 14
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

15. Factors affecting ‘inputs’
Present new information
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

16. Impacts of precipitation on the drainage basin hydrological cycle
Present new information
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.

17. Types of precipitation
Present new information
Construct new meaning

18. Heads and tails: Influxes(inflow of water)
Construct new meaning
Convectional rainfall
A period of sustained, moderately intensive rain; it is associated with the passage of depressions
Cyclonic rainfall
Concentrated on the windward slopes and summits of mountains
Orographic rainfall
Water retained by plant surfaces and later evaporated or absorbed by the vegetation and transpired
Interception loss
This is when water trickles along twigs and branches and then down the trunk
Throughfall
Often associated with intense thunderstorms, which occur widely in areas with ground heating such as the Tropics and continental interiors.
Stem flow
When the rainfall persists or is relatively intense and the water drops from the leaves, twigs, needles etc.
Rain shadow
A dry area on the leeward side of a mountainous area (away from the wind). The mountains block the passage of rain-producing weather systems and cast a "shadow" of dryness behind them.

19. AFL: Heads and tails: Influxes(inflow of water)
Convectional rainfall
A period of sustained, moderately intensive rain; it is associated with the passage of depressions
Cyclonic rainfall
Concentrated on the windward slopes and summits of mountains
Orographic rainfall
Water retained by plant surfaces and later evaporated or absorbed by the vegetation and transpired
Interception loss
This is when water trickles along twigs and branches and then down the trunk
Throughfall
Often associated with intense thunderstorms, which occur widely in areas with ground heating such as the Tropics and continental interiors.
Stem flow
When the rainfall persists or is relatively intense and the water drops from the leaves, twigs, needles etc.
Rain shadow
A dry area on the leeward side of a mountainous area (away from the wind). The mountains block the passage of rain-producing weather systems and cast a "shadow" of dryness behind them.

20. Fluxes in the drainage basin
Present new information
Interception is when water is stored in the vegetation. There are 3 main ways: interception loss, throughfall and stem flow Usually greatest at the start of a storm Interception varies depending on the type of tree e.g. dense needles of a coniferous tree allow for greater accumulation of water.

21. Infiltration variations
Apply to demonstrate
Infiltration -
See page 8 of hodder and p13 of Oxford.
Match up the diagrams with the statements to show how different factors can affect infiltration rates

22. Heads and tails: Flows and Transfers
Construct new meaning
Percolines
The storage of water in streams or rivers
Albedo
Lines of concentrated water flow between soil horizons to the river channel
Evapotranspiration
A measure of the proportion of the incoming solar radiation that is reflected by the surface back into the atmosphere and space
Channel storage
The combined effect of evaporation and transpiration
Potential Evapotranspiration
The water loss that would occur if there was an unlimited supply of water in the soil for use by vegetation

23. AFL: Heads and tails: Flows and Transfers
Percolines
The storage of water in streams or rivers
Albedo
Lines of concentrated water flow between soil horizons to the river channel
Evapotranspiration
A measure of the proportion of the incoming solar radiation that is reflected by the surface back into the atmosphere and space
Channel storage
The combined effect of evaporation and transpiration
Potential Evapotranspiration
The water loss that would occur if there was an unlimited supply of water in the soil for use by vegetation

24. Flows and transfers
Apply to demonstrate
Groundwater -
Match up the flow terms with their definitions and then use them to annotate your version of the diagram above.

25. Drainage basin system outputs
Construct new meaning
Potential Evapotranspiration
Evaporation
Drainage basin system outputs
Use page 10 of Hodder text book to complete
Transpiration
Evapotranspiration
Copy and compete the mind map using the information from page 10 of the Hodder text book

26. What are the physical factors affect the drainage basin cycle?
Present new information

27. 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

28. 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

29. Key processes within a drainage basin and factors that impact upon it
Key processes within a drainage basin and factors that impact upon it. Discuss……and add notes against diagrams
Type of precipitation – Orographic, frontal and convectional
Make notes on this – page 7 hodder or Oxford page 14
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

31. 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
On the next 10 slides I’m going to
explain how each factor impacts
upon processes in the drainage
basin. Use your booklet and make
notes along side the images as
we discuss

32. Basin Shape Construct new meaning
Drainage density depends upon both climate and physical characteristics of the drainage basin. Soil permeability (infiltration difficulty) and underlying rock type affect the runoff in a watershed; impermeable ground or exposed bedrock will lead to an increase in surface water runoff and therefore to more frequent streams. Rugged regions or those with high relief will also have a higher drainage density than other drainage basins if the other characteristics of the basin are the same.
Drainage density can affect the shape of a river's hydrograph during a rain storm. Rivers that have a high drainage density will often have a more 'flashy' hydrograph with a steep falling limb. High densities can also indicate a greater flood risk.

33. Relief
Construct new meaning

35. Temperature and Climate
Construct new meaning

36. Temperature &
Climate
Construct new meaning

37. Land Use
Construct new meaning

38. Rocks types
Construct new meaning

39. Geology – What is it and what influence does it have
Geology – What is it and what influence does it have? (this is a coasts slide from last year)!
Construct new meaning
The red line is an imaginary line that can be drawn to separate different types of geology.
Its called the Tees –Exe Line which roughly divides the country into lowland and upland regions.
To the south and east of this line, the landscape, whilst not always flat is certainly lower and is characterised by flat-lying or gently tilted or folded sedimentary rocks. These areas will have underground water stores
North and west of this line are the older, generally harder rocks including igneous and metamorphic rocks and the Palaeozoic and Precambrian sandstones and limestones which usually stand out as upland areas. These areas will have surface water stores.

40. Soil Types
Construct new meaning

41. Tides and Storms
Construct new meaning
Water level fluctuations include astronomical tides, storm surges, and long-term sea level rise or fall. Water level is important in coastal processes and engineering in part because it controls the location of wave influence on shorelines and structures.
Tides- The tide is the slow rise and fall of the ocean waters in response to the gravitational pull of the moon and the sun
Storms Surges - The rise of water level above the astronomical tide as a result of meteorological forcing. This forcing is primarily wind but also includes the barometric pressure and, for some coast allocations, local rainfall runoff.
Sea level rise/fall - The level of the oceans of the world has been gradually increasing for thousands of years. The important change is the relative sea level change, the combined effect of the ocean water elevation and the land-mass elevation change.
All 3 can have dramatic effects on water levels – surplus which can cause flooding or deficit/shortage which can result in droughts

42. Present new information

43. 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

44. Human factors affect the drainage basin cycle
Homework

45. Homework – complete for next lesson
Construct new meaning
Notes! Use your own file paper
See page 11 – 13 = must make notes!!!
Impact on precipitation - cloud seeding
Impact on evaporation and evapotranspiration – changes in land use
Impact on interception – vegetation types and removal of
See page 12 Hodder and see p15 Oxford within handout - read
Impact on infiltration – changes in land use
Impact on groundwater – irrigation practices and abstraction
Draw diagrams where possible to help your understanding.
Deforestation issues in Amazonia.

46. Homework: Reading & Make extra notes! Essential
Construct new meaning
Read the last 5 pages in the handout and highlight - Very important you understand all key processes an concepts.
2. Research these two different drainage basins and print off:
Amazon, Brazil, S. America – see the Amazonia PDF on weebly for help
Ebro, Spain, Europe
Detail needed taken from specification: Large basins such as the Amazon be used alongside smaller, more localised ones, for instance: semi-arid flatlands, agricultural areas, mountainous. This will help students to distinguish between basin morphology and human influences.
Case studies of basins could be used such as the Ebro (Spain) or the Amazon (Brazil).
Need to develop an understanding of how the movement of clouds and precipitation is affected by the land, such as orographic(affected by mountains) rainfall.
Britannica.com has good information on both

47. Inputs - Precipitation
The amount of precipitation, which can have a direct impact on drainage discharge: as a general rule the higher the amount the less variability in its pattern.
There are six key influencing factors on the drainage basin hydrological cycle.
The type of precipitation (rain, snow or hail): the formation of snow, for example, 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 thaw.
Seasonality. In some climates, such as monsoon, Mediterranean or continental climates, strong seasonal patterns of rainfall or snow will have a major impact on the physical processes operating in the drainage basin system.
Intensity of precipitation is also a key factor as it had a major impact on flows on or below the surface. It is difficult for rainfall to infiltrate if it is very intense, as the soil capacity is exceeded
The distribution of precipitation within a basin. The impact is particularly noticeable in very large basins such as the NIle, where tributaries start in different climatic zones. At a local scale and shorter time time scale the location of a thunderstorm within a small river basin can have a major impact temporarily .
Variability can be see in three ways:
Secular variability happens long term, for example as a result of climate change trends.
Periodic variability happens in an annual, seasonal, monthly or diurnal (daily) context
Stochastic variability results from random factors, for example in the localisation of a thunderstorm in a basin.

48. Storage - Interception
Interception is the process by which water is stored in the vegetation. It has three main components: interception loss, through fall and stemflow.
Interception loss from the vegetation is usually greatest at the start of the storm, especially when it follows a dry period. The interception capacity of the vegetation cover varies considerably with the type of tree, with the dense needles of the coniferous forests allowing greater accumulation of water. There are also contrasts between deciduous forests in summer and in the winter.
Meteorological conditions also have a major impact. Wind speeds can decrease interception loss as intercepted rain is dislodged, and they can also increase evaporation rates.
The intensity and duration of rainfall is a key factor too. As the amount of rainfall increases, the relative importance of interception losses will decrease as the tree canopies become saturated, so more excess water will reach the ground.
There are also variations for agricultural crops, with interception rates increasing with crop density.

49. Flows - infiltration
Infiltration is the process by which water soaks into (or absorbed by) the soil. The infiltration capacity is the maximum rate at which rain can be absorbed by soil in a ‘given condition’ and is expressed by mm/hr. The rate of infiltration depends on a number of factors.
The rate of infiltration also depends on the amount of water already in the soil. As surface or overland flow will take place when the soil is saturated.
The nature of the soil surface and structure is also important. Compacted surfaces inhibit infiltration (around 10 mm/hr), especially when rain slash impact occurs
Slope angle can also be significant: very steep slopes tend to encourage overland runoff, with shallower slopes promoting infiltration
The type, amount and seasonal change in vegetation cover are a key factor, with infiltration far more significant in land covered by forests 50mm/hr and moorland 42 mm/hr. Permanent pasture has infiltration rates of mm/hr depending on grazing density.
Soil texture - whether sand, silt, loam or clay - also influences soil porosity, with sandy soils having an infiltration capacity of 3-12 mm/hr and impermeable clays 1-4 mm/hr
Infiltration capacity decreases with time through a period of rainfall until a more or less constant low value if reached.
Loam - a fertile soil of clay and sand containing humus

50. Flows and transfers
Percolation can be regarded as a continuation of the infiltration process; it is the deep transfer of water into permeable rocks. The through flow percolation route is much more likely to be associated with humid climates with vegetated slopes.
Overland flow/surface runoff is the main way that water is transferred to the river channel. For this type of flow to occur, precipitation intensity must exceed the infiltration rate. Circumstances include an intense torrential rainstorm, persistently high levels of rainfall over a long period of time, or the release of very large quantities of melt water from the rapid melting snow. Alternatively, bare, ‘baked’ unvegetated surfaces, which commonly occur in arid or semi arid regions, also lend themselves to overland flow a this type of land has very little infiltration capacity
Saturated overland flow is a much slower transfer process as it results from the upward movement of the water table in the evaporation zone. After a succession of winter storms the water table rises to the surface depressions (like pits in the land) and at the base of hill sides. This leads to saturated overland flow making a major contribution of channel flow.
Groundwater flow is the very slow transfer of percolated water through pervious or porous rocks. It is a vital regulatory component in maintaining a steady level of channel flow in varying weather conditions.
Through flow refers to the lateral transfer of water down slope through the soil via natural pipes and percolines. While slower than direct overland flow, this shallow transfer can occur quite rapidly in porous, sandy soils.
Channel flow takes place in the river once water from all three transfer process - overland flow, through flow or groundwater flow reaches it
percolines- lines of concentrated water flow between soil horizons to the river channel

51. Outputs
Evaporation is the physical process by which moisture is lost directly into the atmosphere from water surfaces and soil. Evaporation results from the effects of the sun’s heating and air movement, so rates increase in warm, windy and dry conditions. Climatic factors influencing evaporation rates include temperature, hours of sunshine, humidity and windspeed, although temperature is the most important factor. Other factors include the size of the water body, depth of water, water quality, type of vegetation cover and the colour of the surface.
Transpiration is a biological process by which water is lost from plants through minute pores and transferred to the atmosphere. Transpiration rates depend on the time of year, the type and amount of vegetation cover, the degree and availability of moisture in the atmosphere and the length of the growing season.
Evapotranspiration is the combined effect of evaporation and transpiration. It represents the most important aspect of water loss to the atmosphere, accounting for the removal of nearly 100% of the annual precipitation in arid and semi-arid areas, and around 75% in humid areas. Obviously over ice/snow fields, bare rock slopes and soils, desert areas and the majority of water surfaces, the losses are purely evaporative.

52. Make a copy of the diagram for revision – learn it!
Review
Make a copy of the diagram for revision – learn it!
Use your diagram to describe how the drainage basin cycle works – complete for revision

53. The Hydrological Cycle
Review
NASA: