Page 1 of 22
Prepared & brought
To you with love by
IGCSE / O’LEVEL
GEOGRAPHY TOPIC NOTES
TOPIC:
Rivers and Waters
We offer students for 100% free with Notes & Handouts for all subjects, full online books
library, lecture interactive explanatory video tutorials, discussion hub with online classes
and study groups which students can join, can post questions troubling them while other
students and our tutors from different schools, academic backgrounds and countries all
over the world can help with necessary help through comments or private messages.
***** Free quality, education for all!!*****
Page 2 of 22 All rights reserved no part of these Notes handouts or any other CIOHS resources may be
reproduced for any commercial uses or edited in any form without prior copyright permission from CIOHS. However genuine printing, sharing without editing copyright water marks and branding is allowed. Feel free to contribute to our resources and services as we are currently looking for contributors and volunteers who are willing to help us as a non profit organization to make our impact and touch students lives from all over the world.
PREFACE & MESSAGE FROM CIOHS CEO, FOUNDER AND DEVELOPER
Warm greetings to you and it is my utmost pleasure and joy if you are reading this message,
as it means our goal and vision to help every student from around the world is being
achieved. As a student who grew up and studied experiencing difficulties in accessing quality
study materials like notes, handouts and textbooks, good career guidance, assistance and
help on problematic areas I felt very moved and captivated with the zeal and passion to
solve this problem. Therefore it is my pleasure presenting this technovation to all students
from around the world irrespective of age, sex, race, location and etc. Henceforth I wish all
students the best in their endeavors. My message and words to them are happy studying,
feel free to use CIOHS whenever you feel the need to do so and don’t hesitate to
communicate with us. We are there to serve you and help you achieve your academic goals
if you need any resources in line with resources and services we offer. This platform took
me lots of time, dedication and sleepless nights working on it so iIt will be my pleasure
seeing students benefiting at large from this service, so please consume this benefit wisely
for your benefit and future, please don’t abuse it.
Thank you
From
Collins Jimu (CIOHS CEO, Founder and Developer)
Page 3 of 22
RIVERS AND WATER
Key Terminology
• Condensation: The cooling of a gas so that it changes into a liquid, for instance
as water vapour cools, it condenses to become water droplets, which, when heavy enough, fall as rain.
• Confluence: Where two rivers meet and join to form one larger river.
• Delta: A build up of sediment at the point where a river meets a sea or lake, due
to the water velocity slowing and the river having less energy to carry the sediment.See later section for details.
• Drainage Basin:The area of land drained by a river and its tributaries.
• Estuary: The point at which a river begins to meet the sea. The river will be
tidal, meaning that it will have both salt water and fresh water in it.
• Evaporation: Water that is warmed, usually by the sun, so that it changes into a
gas (water vapour).
• Evapo-transpiration: The combination of evaporation and transpiration.
• Fluvial: relating to a river, from the Latin for water.
• Groundwater: see Percolation
• Hydrology: The study of water
• Infiltration: The downward movement of water that seeps into the soil or a
porous rock.
• Mouth: The end of the river, where it meets the sea, or a lake.
• Overland Flow: When water flows over the surface of the ground. This occurs
Page 4 of 22
• Percolation: The movement of water through the soil or underlying porous
rock. This water collects as groundwater.
• Precipitation: Waterfalling to Earth in any form: e.g. rain, sleet, hail, snow, and
dew, all are encompassed by the term precipitation.
• Surface Run-off: see Overland Flow
• Throughflow: the movement of water with in the soil sideways, towards the
river.
• Transpiration: The water loss from vegetation into the atmosphere.
• Tributaries: rivers running into the main one, that form part of the same
drainage basin system.
• Velocity: The speed of the flow of the river.
• Watershed: The imaginary dividing line between neighbouring drainage
basins.
The drainage basin system (as part of the water cycle)
The drainage basin of a river forms an integral part of the entire hydrological cycle (also known as the water cycle), which is shown in the diagram below. The drainage basin acts as an open system,with a number of inputs, outputs, stores and transfers.
The main input into the system is precipitation, mainly as rainfall, but also as things such as snow, sleet and hail.
This water is then transferred through the system by the processes of infiltration,percolation, overland flow and throughflow.
Page 5 of 22
Finally the water will reach the river, which is the primary out put to the system. However water will also have already been lost due to the processes of
evaporation, transpiration and evapo-transpiration.
These are also shown in the diagram below: Drainage patterns
As water flows downhill into rivers it can createa number of different drainage patterns. These are primarily influenced bythe underlying geology (rock type) of the area
Centripetal
• The rivers flow inwards towards a point.
• Occurs due to the underlying rock forming a basin.
• Examples include the Sea of Galilee
Dendritic
• The rivers form a tree shape, with the primary river forming the trunk.
• Occurs in areas where the rock type is uniform (it is all the same)
• Examples can be found commonly throughout the world, and include the Mississippi, in the United States.
Page 6 of 22
• The rivers run parallel to each other downhill.
• The underlying rock is uniform and the surface is flat
Radial
• The rivers flow outwards from a central point.
• The underlying rock has been uplifted to become a dome, or may be a cone of a volcano.
• Examples include the uplifted granite dome of Dartmoor, or the perfect volcanic cone of Mt. Taranaki in New Zealand.
Trellis
• The river and its tributaries run parallel to each other, before turning at right-angles to meet up.
• The underlying rock is an alternating structure of resistant and less resistant rock.
• The main river, which flows in the direction that the underlying rock dips, is called the Consequent River. The tributaries flowing into it are called
Subsequent Rivers.
• Long profiles
Page 7 of 22
•
• Cross profiles
• The cross profile of the river channel changes throughout the course of
the river. In the upper section the channel tends to be quite narrow, and comparatively deep. The bottom and sides are littered with many boulders and rocks, causing a great deal of friction for the water flowing past them. This slows the water down and means that this is where the river is
flowing the slowest.
• In the mid course of the river has a wider channel, which is deeper than
the one in the upper reaches, and the water flows faster, as it has less material to slow it down. The river may begin to meander in this section.
• The lower course sees the river flowing at its fastest until it slows down
when it meets the sea. The channel is very wide, deep in places where the water is flowing quickest, and smooth sided.
River profiles overview
Upper Course Mid Course Lower Course Long Profile Steeply sloping towards the lower sections of the river.
Shallow slopes towards the mouth of the river.
Almost at sea level, very gently sloping towards its mouth.
Cross Profile Steep sided v-shaped valley. Thin river channel, deep
V-shaped valley remains with a wider valley floor and the river begins to meander across it. The
Page 8 of 22
in places. river channel begins to widen and become deeper.
deep and smooth sided.
River processes
River processes shape the land in different ways as the river moves from its source to its mouth. Erosion, deposition and materials rivers carry all contribute to how rivers shape surrounding land.
Erosion
Erosion involves the wearing away of rock and soil found along the river bed and banks. Erosion also involves the breaking down of the rock particles being carried downstream by the river.
The four main forms of river erosion
• Hydraulic action - the force of the river against the banks can cause air to be
trapped in cracks and crevices. The pressure weakens the banks and gradually wears it away.
• Abrasion - rocks carried along by the river wear down the river bed and
banks.
• Attrition - rocks being carried by the river smash together and break into
smaller, smoother and rounder particles.
• Solution - soluble particles are dissolved into the river. Transport
Rivers pick up and carry material as they flow downstream.
The four different river transport processes
• Solution - minerals are dissolved in the water and carried along in solution.
• Suspension - fine light material is carried along in the water.
• Saltation - small pebbles and stones are bounced along the river bed.
Page 9 of 22
Rivers need energy to transport material, and levels of energy change as the river moves from source to mouth.
• When energy levels are very high, large rocks and boulders can be
transported. Energy levels are usually higher near a river's source, when its course is steep and its valley narrow. Energy levels rise even higher in times of flood.
• When energy levels are low, only small particles can be transported (if any). Energy levels are lowest when velocity drops as a river enters a lake or sea (at the mouth).
Deposition
When a river loses energy, it will drop or deposit some of the material it is carrying.
• Deposition may take place when a river enters an area of shallow water or when the volume of water decreases - for example, after a flood or during times of drought.
• Deposition is common towards the end of a river's journey, at the mouth.
• Deposition at the mouth of a river can form deltas - for example, the
Mississippi Delta.
River landforms
River landforms can be divided into upper, middle and lower course features. These include steep V-shaped valleys, oxbow lakes and flood plains,
respectively.
Upper course features
Upper course river features include steep-sided V-shaped valleys, interlocking spurs, rapids, waterfalls and gorges.
Middle course river features include wider, shallower valleys, meanders, and oxbow lakes.
Page 10 of 22
Upper course river features
As the river moves through the upper course, it cuts downwards. The gradient here is steep and the river channel is narrow. Vertical erosion in this highland part of the river helps to create steep-sided V-shaped valleys, interlocking
spurs, rapids, waterfalls and gorges.
• As the river erodes the landscape in the upper course, it winds and bends to avoid areas of hard rock. This creates interlocking spurs, which look a bit like the interlocking parts of a zip.
• When a river runs over alternating layers of hard and soft rock, rapids and waterfalls may form.
Middle course features Meanders
Page 11 of 22
• As the river erodes laterally, to the right side then the left side, it forms large bends, and then horseshoe-like loops called meanders.
• The formation of meanders is due to both deposition and erosion and meanders gradually migrate downstream.
• The force of the water erodes and undercuts the river bank on the outside of the bend where water flow has most energy due to decreased friction.
• On the inside of the bend, where the river flow is slower, material is deposited, as there is more friction.
• Over time the horseshoe become tighter, until the ends become very close together. As the river breaks through, eg during a flood when the river has a higher discharge and more energy, and the ends join, the loop is cut-off from the main channel. The cut-off loop is called an oxbow lake.
Oxbow lake
Page 12 of 22
Lower course features
In the lower course, the river has a high volume and a large discharge. The river channel is now deep and wide and the landscape around it is flat. However, as a river reaches the end of its journey, energy levels are low and deposition takes place.
Floodplains
The river now has a wide floodplain. A floodplain is the area around a river that is covered in times of flood. A floodplain is a very fertile area due to the
rich alluvium deposited by floodwaters. This makes floodplains a good place for agriculture. A build up of alluvium on the banks of a river can create levees, which raise the river bank.
Deltas
Deltas are found at the mouth of large rivers - for example, the Mississippi. A
delta is formed when the river deposits its material faster than the sea can remove it. There are three main types of delta, named after the shape they create.
Arcuate or fan-shaped - the land around the river mouth arches out into the sea
Page 13 of 22
The Niger Delta
Cuspate - the land around the mouth of the river juts out arrow-like into the sea.
Page 14 of 22
Bird's foot - the river splits on the way to the sea, each part of the river juts out
into the sea, rather like a bird's foot.
The Mississippi Delta RIVER BASINS
The uses of river basins
For thousands of years, rivers have been the focal point of people's activities. Some of these are listed below:
• Rivers provide a source of fresh drinking water, a source of food (fishing) and a
Page 15 of 22
• Flood plains provide areas of rich, fertile alluvial soil. Hence areas like the
Canterbury plains in New Zealand are intensively farmed.
• Rivers can act as a very effective power source. Initially waterwheels were used to power factories during the Industrial revolution. Latterly the development of hydroelectric power has meant a great increase in the building of dams to trap the water of a river and its drainage basin.
• Rivers have always been seen as a convenient way of waste removal. This has led to many rivers becoming very polluted and in some cases, dangerous.
• Estuaries commonly have been used for industry, which has been able to build
its factories on the flat flood plain land. This location is ideal for many industries, such as oil refineries, as they then have easy access to the sea for transporting their goods. The land is flat, cheap and easy to reclaim. Usually a local labour source is not too far away. The ship building industry used also to be found in the estuaries of many of the great rivers around Britain, such as the Clyde and the Mersey. Now only a few remain.
Page 16 of 22
As humans have increasingly used and abused river basins so management and planning of them has become increasingly important.
• Flooding is the most common thing to have to plan around. In many cities the
flood plain has not really been built on. Oxford, Exeter and Salisbury are all good examples of where this is the case.
• To prevent the impact of flooding schemes have been introduced in many of these places. These methods can be very successful, or can cause greater problems further downstream. In Exeter, flood relief channels and raised riverbanks have been used to diminish the flood risk. The scheme in place is aimed at countering a "once in one hundred years" flood, and has been severely tested a couple of times.
• Building dams across rivers can also cause problems. Obviously there are the advantages of creating a large reservoir, which can be used for drinking water or as the source of water for a hydroelectric power scheme. The reservoir will often also be used for recreational purposes. However the building of a large dam can also cause problems by affecting the flow of water further down the river, by flooding areas of farmland and even towns or villages,and by affecting entire ecosystems.
• The Tucurui Dam in the Northern Brazilian rainforest did just this, flooding an area of 2875 square kilometres. It was built to provide power for local
industries, but at quite a price. The lake it created displaced 40,000people, and is estimated to have destroyed hundreds of species of animals and plants, some of which may never have been actually known about.
• Rivers are used for the dumping of waste, such as sewage, agricultural waste, chemicals and oil. All will greatly harm the wildlife of the river as well as
causing potential problems for humans when they drink the water. Schemes and by-laws have been introduced to try to prevent the pollution of our rivers.
The global demand for water
Page 17 of 22
Water usage of LEDCs and MEDCs
What the water is used for depends on the country.
• In general, LEDCs (like Bangladesh and Malawi) will have most of their water used in agriculture (farming) and little in industry or domestic use. Bangladesh has farming as a large part of its economy so a large percentage of their water is used for that purpose.
• MEDCs (like the UK) have a more significant use of water for domestic reasons. MEDCs also tend to have a higher percentage for industrial use.
• There are exceptions. The USA is an MEDC, but it still has a high amount of water used for agriculture because there is also lot of farming across the country.
Water used per person
The amount of water used per person in each country changes dramatically. The bar chart shows the total amount of water used per person in selected countries.
Page 18 of 22
What is water used for in LEDCs and MEDCs? Agriculture
• In MEDCs irrigation is mechanised. Sprinklers or timed irrigation feeds are
used. Where agriculture is common, vast amounts of water can be released at the touch of a button.
• In LEDCs irrigation channels are prone to losing water through evaporation.
Industrial use
• Industries in MEDCs can be on a large scale, and so demand a lot of water. The steel industry is an example of an industry which needs a large water supply for manufacturing purposes.
• LEDCs have smaller scale cottage industries. They demand less water in the
production of items. However as more multinational companies locate in LEDCs there will be more demand on water. For example, in India, drinks manufacturers use over a million litres of water a day to produce drinks.
Domestic water use
• In MEDCs there are a lot of facilities which demand water use. For example, showers, baths, washing machines and swimming pools.
• In LEDCs many people do not have access to piped water and so use it more sparingly. Water may be brought to the home from a well or stream.
As a country becomes more wealthy, there will be an increase in its demand for water. Higher levels of industrialisation and more domestic goods such as
washing machines all lead to an increase in demand for water. With greater wealth there is also more demand for spas, golf courses and even baths and showers.
Management of water usage in MEDCs
There are problems in supplying water in MEDCs. These are:
Page 19 of 22
• the seasonal changes in supply
• broken pipes when transporting water
Both water supply and the demand for water need to be managed.
Managing water supply
In the UK there is a big issue with water supply. Areas which receive high amounts of rainfall tend to be sparsely populated.
One third of the UK population live in south-east England. This is also the driest area in the UK.
Ways to manage the water supply include:
• making sure the broken pipes are mended (as water loss from broken pipes
can be as much as 30 per cent)
• using reservoirs and dams in one area to pipe water into large urban areas
• making sure that the water supply is of good quality - reducing fertiliser use on farms helps this
In December 2010, over 40,000 people had water supply problems in Northern Ireland. One reason was because the water pipes were quite old - some over 60 years old. This meant that when there was a spell of very cold weather, many pipes could not cope and the pipelines failed.
Managing water demand
The demand for domestic water can be monitored. Households with water meters in the UK use less water in general than those without. Households can also conserve water. Ways to do this are:
• having a shower instead of a bath
• collecting rainwater to use on the garden rather than tap water
• recycling bath water to flush the toilets with
Page 20 of 22
Industries can also look to recycle waste water. For example, when using water for cooling in steel-making, the water can be recycled again and again in the process.
In agriculture, drip-feed irrigation systems could be used rather than sprinkler systems.
Management of water usage in LEDCs
There are problems in supplying water in LEDCs. These are:
• lack of availability of clean water
• diseases spread via the water supply
• water pollution
Managing water resources
One in eight people of the world population do not have access to safe water. 60 million children are born each year in LEDCs who do not have access to safe water.
In LEDCs using appropriate technology is usually the best way to manage supply.
• Wells, dug by hand, are a common way of accessing water, but the supply
can be unreliable and sometimes the well itself can be a source of disease.
• Gravity-fed schemes are used where there is a spring on a hillside. The water can be piped from the spring down to the villages.
• Boreholes can require more equipment to dig, but can be dug quickly and usually safely. They require a hand or diesel pump to bring the water to the surface.
In addition to locating new sources of water, some strategies help to reduce the need for water. These include:
• harvesting (collecting) rainwater landing on buildings
Page 21 of 22
• improving irrigation techniques
• growing crops less dependant on a high water supply
• minimising evaporation of water
As LEDC cities grow, so does the demand for water. The problem doesn't end when water supplies have been improved and pipes put in place. The water has got to come from somewhere, and the source of supply may be scarce. It is LEDCs which have the lowest access to safe water
Managing safe water
Without safe water, people cannot lead healthy and productive lives. Areas which are in poverty are likely to remain in that way. One example where non-governmental charities have helped break this cycle is in Nigeria.
In Nigeria only 38 per cent of people have access to sanitation. A community led total sanitation project (CLTS) was started by one non-governmental charity. In one year, the project helped 2.5 million people gain access to
Page 22 of 22