Higher Geography
N6
Hydrosphere
Name: _______________
NOTES BOOKLET
1
Unit: Physical Environments
Outcomes and Assessment Standards
Outcome 1
1
Use a range of mapping skills and techniques in physical
environment contexts by:
1.1. Interpreting complex geographical information from at least two
sources
1.2. Annotating a geographical resource
1.3. Presenting complex geographical information
1.4. Analysing geographical information
Outcome 2
2
Draw on and apply knowledge and understanding of the
processes and interactions at work within physical
environments on a local, regional or global scale by:
2.1 Giving detailed descriptions and detailed explanations of a
process/ interaction at work in a physical environment
2.2 Giving detailed descriptions and detailed explanations of the
impact of weather systems and/climate within a physical
environment
2.3 Giving detailed descriptions and detailed explanations of a
complex issue in a physical environment
2
Hydrosphere Checklist
By the end of this topic you should be able to:

draw a diagram to show the global hydrological cycle

describe the global hydrological cycle shown on a diagram

explain how balance is maintained within the hydrological cycle

explain how water moves within drainage basins.
Use an OS map to:

describe the physical characteristics of a river and its valley

compare and contrast the physical features of two rivers and their valleys

Annotate a base map to show the physical characteristics of a river and its
valley.
With the aid of a diagram(s):

explain the effects of flowing water in terms of erosion, transportation
and deposition in the upper, middle and lower course of a river

Describe and explain the patterns shown on a river hydrograph.
Skills

annotate sketches and diagrams to describe and explain river features

construct and analyse river hydrographs to show the relationship between
rainfall and river flow

describe methods used to collect river-flow data: e.g. measuring depth,
width, speed, gradient

describe methods used to present river-flow data: e.g. labelling sketches,
drawing cross-sections, showing speed, drawing graphs including scatter
graphs to show relationship between speed and gradient

Comment on the accuracy of statements which refer to river
characteristics.
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Physical Environments: Hydrosphere
Introduction
The word ‘hydro’ means water. Hydrology is the scientific study of water at the
earth’s surface and its links with the atmosphere. Without water there would be
no life on earth. Water is therefore a very important aspect.
Only 3% of the water on earth is fresh water and only a third of that (1%) is
available to us:

97% is sea water

2% of water is locked away in glaciers and ice caps

1% is fresh water and available for human use (ground water, lakes
and river).
Although a person can live without food for more
than a month, a person can only live without water
for approximately one week! 70% of the world’s
population do not have pure water. Everyday 25,000
people die from waterborne diseases! For Example
the average Kenyan uses around 4 litres of water
per day. One person in New York, however, consumes 680 litres per day!
Water is therefore essential to life and human beings rely on the continual cycle
of water known as the Hydrological cycle.
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What is the Global Hydrological Cycle?
The Hydrological Cycle describes the continuous movement of water on, above
and below the Earth’s surface. It is a closed system. The hydrological cycle is a
major cycle which links all the elements of our environment. The model involves a
continual circulation of water between the oceans, the atmosphere, vegetation
and the land. It is what we call a closed system. In other words, no water can
enter or leave the system.
1. Evaporation: Solar heat evaporates water into the air from the Earth's
surface. Land, lakes, rivers and oceans send up a steady stream of water
vapour;
2. Transpiration: plants and trees release water vapour through transpiration
and this rises into the atmosphere.
3. Condensation: The water vapour in the atmosphere raises, cools and
condenses to form clouds. This spreads over the surface of the planet
before falling down again as precipitation
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4. Precipitation: Clouds pass over high ground and begin to fall as
Precipitation. Water falls on land and is the main source (input) for rivers,
lakes, groundwater and glaciers.
5. Surface runoff: water enters river courses and is found on the land
surface e.g. lakes and rivers. This water eventually flows into the sea to
complete the cycle.
6. Infiltration: This is the process by which water seeps into the soil and sub
soil which eventually can become saturated.
7. Water Table: the level that the soil is saturated is known as the Water
Table
8. Percolation: Water continues to move into the ground through soil to sub
soil creating groundwater. Groundwater is water that is stored in rocks
underground
Task 1: Complete the following task in your booklet
Explain, with the aid of annotated diagram the global hydrological cycle (6)
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The River Drainage Basin System
In the Hydrological cycle, rivers are the critical link between the atmosphere and
oceans. Rivers and their tributaries form networks which transport water and
erode materials, sometimes at high speeds and in vast volumes from land to sea.
The area around a river is called a Drainage Basin.
A drainage basin is part of the hydrological cycle and may be viewed as an
individual system with inputs, storage and outputs. A drainage basin is the
catchment area of a stream and tributaries. The boundary is called the
watershed. The drainage basin can be seen as a system:
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Inputs
Output
Moisture entering the system i.e. precipitation.
All moisture which leaves the system i.e. by
evaporation.
This is the movement through the system, e.g.
Transfers
within the air, precipitation, ground seepage and
infiltration.
Storage
Moisture contained within the system e.g. in soil,
lochs, ice, rivers and ground.
Task 1: Thinking Skills
(a) On your diagram of the hydrological cycle identify inputs, storage,
flow/transfer and output by selecting a colour in the key.
(b) On your diagram of the water catchment add the statements from the
PowerPoint in the correct location.
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Main characteristics of the drainage basin system
Inputs:

The main input to the drainage basin is through precipitation
Storage:

Stored water is held within the drainage basin system in lakes/lochs this is
known as surface storage.

Water can also be stored by being absorbed by soils and stored by trees
this is known as interception.

The amount of water that can be stored as groundwater depends on the
rock type underlying the soil. If the rock is porous (like a sponge) the
water may be held .

Human activity can also interrupt the flow of water as water can be
dammed by HEP to create reservoirs to produce electricity or fresh water;
furthermore increased forestry plantations in a catchment will store more
water.
Transfers/Flows:

Water transfers through tributary and river courses known as surface
runoff.

Water can transfer by infiltrating through soil and transfer through the
soil known as through-flow

Water can then percolate through rock this is known as infiltration. The
water transfers through the rock this is known as groundwater flow.

During periods of heavy rainfall the soil and sub-soil may become saturated
resulting in an increase in surface run-off.
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
Sub rock may be impermeable (can’t hold water) meaning it contribute to
the groundwater flow
Output:

Evapotranspiration is the combined return of water into the atmosphere by
evaporation and transpiration. Evaporation is the water loss from the
ground or water surfaces due to the heat from the sun. Transpiration is
water loss from vegetation.

River courses eventually return water through the drainage system
through surface runoff and condensation
Task 2
Discuss the movement of water within a drainage basin with reference to the
four elements above (7)
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The Drainage Basin System:
Erosion, Transportation & Deposition
There are three main processes in the way that a river ‘works’. These are:
1. Erosion
2. Transportation
3. Deposition
1. Erosion
The amount of erosion a river can achieve depends on its energy or discharge. A
river’s energy increases with its volume, velocity and seasonal flow.
Erosion in a river is caused by 4 processes:

Attrition – when boulders, rocks and pebbles crash in to each other and
bits break off therefore being rounded and reduced in size.

Abrasion– the wearing away of the river bed and the banks by the river’s
load. This is the main method of erosion.

Hydraulic Action – the sheer force of the river breaks off particles from
the river bed and banks.

Corrosion (Chemical Solution) – dissolving of minerals from the rocks.
A river’s valley is deepened by vertical erosion – entirely a river process. A
river’s valley is widened by lateral erosion – affected by weathering on the valley
sides and by the river on the river banks.
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2. Transportation
A river transports its load in 4 ways:

Traction – dragging of pebbles, gravel along its bed.

Saltation – bouncing of the load.

Suspension – light sediments of silt and clay are held in suspension by the
river’s turbulence (the greater the turbulence, the greater the size of
particles which can be held).

Solution – chemicals are dissolved in the water.
3. Deposition
Sediments are transported by a river until it has insufficient energy to move
them further and deposition takes place.
A river may lose its energy where:
 There is a decrease in gradient.
 There is widening or meandering of its channel.
 There is an increase in load.
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Profile of a River Drainage Basin
A drainage Basin can be divided into three sections – the Upper, Middle and
Lower courses.
The Upper Course
The upper stretches of a river are rocky, often being covered with
Channel shape
boulders of different shapes and sizes. The river channel is usually
narrow and fairly straight.
Valley features
The valley is a V-shape in the upper course, meaning it is very narrow.
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As the river is fast flowing it has a high amount of energy to erode.
This erosion usually happens vertically as the river bed cuts down into
Main processes
the valley floor. The main types of erosion operating in this stage of
the river are hydraulic action and corrosion, due to the fast flowing
nature of the water. Potholes form where pebbles and cobbles,
rotated by swirling eddies, grind deep holes in the bedrock.
The gradient is usually very steep in the early stages causing the
Gradient
river to be fast flowing. This encourages the main work of the river
to be erosion.
Under normal conditions the discharge is fairly low.
Discharge
Rivers load
Boulders of varying shapes sizes occupy the river bed. Large stones
and rocks travel down the river channel by traction and saltation.
The Middle Course
Channel shape
Valley features
Main processes
The channel is now wider and deeper and has smoother banks and
floor.
The valley sides are less steep and there is a more gentle gradient
As the valley has flattened out the river starts to expend its energy
horizontally rather than vertically.
The gradient becomes less steep but the river remains fast flowing
as it has a smoother channel to flow through. Erosion and deposition
can now be found in the middle course. Erosion mainly takes place on
Gradient
the outside of meanders where the current is faster and the river
has more energy. Deposition takes place on the inside of meanders
where the current is slow flowing and therefore does not have the
energy to carry it’s load.
Discharge
The discharge of the river increases as more tributaries flow into
the main channel.
Traction and saltation still play an important part in transporting the
Rivers load
rivers load. However, more of the rivers load is ground down through
attrition so that silt and clay sized particles are carried in suspension
and are increasingly deposited.
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The Lower Course
Channel shape
Valley features
Main processes
Gradient
Discharge
Rivers load
The channel is now at its broadest and deepest.
Due to lateral erosion valley sides may be several kilometres away.
The valley is dominated by wide floodplains.
Deposition is now the dominant process particularly during floods
when the rivers load is spread out over the valley floor.
The gradient is now very gentle and in some cases may appear totally
flat. This encourages deposition to take place.
The discharge of the river is at its greatest as large volumes of
water pour out into the sea.
The river’s load is carried entirely in suspension and solution
consisting mainly of fine sediments.
Task 1: Profile of a River
Complete the profile of a River task
Task 2:
Explain the effects of flowing water from the upper to the lower course of the
drainage basin.
Discuss in terms of erosion, transportation and deposition. (8 marks)
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Human Impact on the Hydrological Cycle
Human demands on the world’s fresh water
supplies have greatly increased through time due
partly to population increase. Domestic use also
makes huge demands upon fresh water
resources, especially in developed countries. By
far the largest percentage of water in these
countries is used for just three main purposes –
flushing toilets, washing and bathing. The other
main uses of water are:
-
in industry
-
in the food and drink industry
-
in agriculture (irrigation especially)
Interference in the Hydrological Cycle
In order to cater for ever-increasing human demands for fresh water, it is
necessary to ‘intervene’ with the hydrological cycle to meet human requirements.
Humans tend to extract water at run off stage (from rivers and streams) or
storage stage (groundwater and lakes). However this is much more difficult in
areas where the climate is dryer and water is in short supply.
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Deforestation
Within Developed countries a major land use in the drainage basin system is
forestry as a result forests are deforested for commercial purposes. In
Developing countries forests are deforested for a number of reasons. Within the
drainage basin system trees store water, however, if trees are cut down less
water is stored and therefore there is an increase in surface run off and through
flow. There is also a decrease in evapotranspiration resulting in less water being
added to the cycle and an overall increase in river flows.
Irrigation
Water is used in farming to irrigate land and crops to increase farming output.
Farmers take water from the water table and aquifers to irrigate their land.
Furthermore, farmers store water to use for irrigation purposes. This can reduce
water flow within the drainage basin.
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Urbanisation
Increased urbanisation results in the removal of natural vegetation with the
replacement of impermeable surfaces such as concrete which will ultimately
increase surface runoff through the system. Man-made drainage and sewage
systems returns water back in the drainage basin system much quicker which
results in higher river levels. Furthermore the amount of water that is quickly
returned into the drainage system results in less water entering the ground
water storage reducing the water table.
Dams, Reservoirs and HEP
Due to increasing demand for fresh clean water and in renewable energy sections
of the drainage basin are dammed to store water within a catchment. The water
is stored and used for drinking water and HEP. As a result the water is
intercepted and cannot complete the hydrological cycle. This then reduces the
flow of water through the drainage system.
Task 1:
Analyse how human activity, such as those shown on Diagram Q2A, can impact on
the hydrological cycle.
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Hydrographs
A hydrograph may be used to show how the water flow in a drainage basin
(particularly river runoff) responds to a period of rain. This type of
hydrograph is known as a storm or flood hydrograph and it is generally drawn
with two vertical axes. One is used to plot a line graph showing the discharge
of a river in cumecs (cubic metres per second) at a given point over a period of
time. The second is used to plot a bar graph of the rainfall event which
precedes the changes in discharge.
A Hydrograph has a number of main characteristics:

Precipitation – shown as a bar graph but sometimes not always shown

Base Flow – flow supplied by groundwater. This is the normal flow of the
river
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
Rising Limb – represents the rapid increase in the height of the river due
to precipitation. Various factors can affect how quickly the rising limb
rises.

Peak discharge shows the highest point of the river flow

Quick flow/Storm Flow – flow supplied by overland flow and soil through
flow. This gives the peak flows.

The falling limb shows the river level returning to normal
Task One:
Using the data given on page 8, construct a hydrograph in the graph template provided.

Rainfall (mm) will be presented as a bar graph

Discharge (m3/s) will be presented as a line graph
Interpretation and Analyse of Hydrographs
You will be expected to interpret a hydrograph and to give a detailed analyse of
its shape. There are a number of factors which influence the shape (rising limb)
of a hydrograph.
A steep rising limb and short lag time can be caused by:
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Graph B
Graph A
A
B
Steep slopes
Gentle slopes
No Trees
Forested
Impermeable rocks
Permeable rocks
Urbanised
Fields
Intense thunderstorm
Light steady rain
A gentle rising limb and long lag time can be caused by:
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Task Two:
Analyse the Hydrograph you created and explain in detail the factors which have
influenced its shape. (8 marks)
When answering these types of questions you must not only describe the
features of the hydrographs, but explain why the hydrographs have certain
shapes. You should think about what effects on the hydrograph the following
have:
 Size of the drainage basin
 Steepness of the slopes
 Rock or soil type (Permeable or Impermeable?)
 Stream density
 Vegetation
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