THE WATER CYCLE
KEY ISSUES
• Importance of Water
• The Water Cycle
• Water Demand
1. The Importance of Water
Water is the most important substance on earth. It is made up of
two gases at the rate of two parts Hydrogen to one part Oxygen,
hence H2O. It can appear in three different forms, depending on
the temperature. As a solid, we call it ice, as a liquid, we call it
water, and as a gas, we call it water vapour. Seventy per cent of
the earth’s surface is covered by water and 90% of all life found
on earth lives in water. No living thing on earth can survive
without water. Water is the element essential for life, but perhaps
its most amazing quality is its ability to recycle itself. This is called
the Water Cycle.
Spray irrigation is used by farmers to water crops
No. 3 in a series of Educational Fact Sheets
2. The Water Cycle
All rivers and reservoirs from which we extract water are part of a
cycle. Surface water either flows to the sea or evaporates as a gas
to form clouds. These clouds, made up of tiny water droplets,
increase in size and eventually drop. They fall as snow or, melt as
they meet warmer temperatures to fall as rain. Water falling from
the sky in any form is called precipitation.
An example of surface
water flowing through
the countryside in the
form of a river
Once the water hits the earth’s surface, some of it will be
evaporated back into the atmosphere, some will soak into the
surface soils and some will remain on the surface. Some rocks
beneath the soil are permeable, that is, they allow water to pass
through. This is called infiltration, or percolation, as water flows
down through the rock, because of gravity, until it meets an
impermeable barrier such as clay, which does not allow water to
pass through. Here it will collect to form a natural underground
reservoir called an aquifer. The upper level of this saturated zone
(porous rock containing water) is called the water table. If the
water table meets the surface, then water will appear bubbling
up through a spring, forming streams such as those that flow
into the River Wissey in Norfolk.
If the rain falls onto an impermeable surface, it will not soak into
the rock. Instead, it will begin by collecting in puddles on the
surface before it starts to flow downhill, forming rivulets or tiny
streams. As these flow downhill, they become larger, forming
rivers, and as more tributaries (smaller streams) join, they flow
into a lake or the sea. Once the water arrives back in the sea, the
whole cycle begins again with evaporation.
Not all the water will continue this cycle uninterrupted. Some
water will be intercepted. Plants will suck water up through their
roots, passing it through their leaves by the process of
transpiration. Water is also intercepted and used by people. In
effect, they borrow it from the water cycle, returning it when it
has been used.
Cloud
Precipitation
Transpiration
Spring
River
Soil
Infiltration
Water Table
Aquifer
Impermeable Rock
Estuary
Evaporation
Sea
3. Water Demand
Water is an essential commodity of life.
Increasingly large amounts of water are being
used by people. We use water for drinking, cooking,
cleaning and disposal of waste products. On average we
each use about 140 litres of water per day.
In addition to our own use of water at home, there
are national demands for water use from business
and industry, farming and large institutions such as hospitals.
Farmers are dependent on water to grow the crops we eat and
factories need the water in manufacturing processes. It can also
provide a cheap means of transport for large amounts of goods
and cargo, and offers very popular forms of recreation such as
swimming, fishing and boating. It is the role of the water
companies is to provide a clean water supply; the role of the
Environment Agency is to balance the water needs of people
with the needs of the environment. The Agency aims to achieve
secure water supplies and a better water environment.
WATER SUPPLY
It is the role of the Agency to ensure that a balance is maintained,
reducing the effects of droughts, with shortages of water, and
floods with too much water. Within the Agency, it is the
responsibility of the Water Resources Department to maintain
adequate water levels. The Anglian Region has a particular
problem because demand is higher in the summer months when
evaporation is also at its highest. Water supply in the summer is
maintained from groundwater naturally stored in aquifers. In
some places, artificial reservoirs have also been built to even out
supply through the year. Here, water is stored behind huge
dams, creating large lakes such as the one at Rutland Water. This
is then pumped through pipes when and where it is needed.
Did you know?
Here are the basic requirements for
water, and figures for some
countries around the world. Notice
the huge difference between
developed countries and third world
countries.
Basic Daily Water Requirements
litres/person/day
Drinking water . . . . . . . . . . . . . . . .5
Flushing toilets . . . . . . . . . . . . . . .20
Bathing . . . . . . . . . . . . . . . . . . . . . .5
Cooking/kitchen . . . . . . . . . . . . . .10
TOTAL . . . . . . . . . . . . . . . . . . . . . .50
Some Average Consumption Figures
litres/person/day
Gambia . . . . . . . . . . . . . . . . . . . . . .9
Bangladesh . . . . . . . . . . . . . . . . . .17
Germany . . . . . . . . . . . . . . . . . . . .32
GB . . . . . . . . . . . . . . . . . . . . . . . .150
USA . . . . . . . . . . . . . . . . . . . . . . .473
THE WORK OF THE
ENVIRONMENT AGENCY
In order to protect and care for this valuable resource, the
Agency carries out continuous measurements of the amount of
water in the water cycle. This is known as Hydrometry. There are
three main stages in the water cycle where measuring occurs:
• Rainfall
The traditional method of measuring rainfall is still carried out
daily at 500 sites throughout the region. A collecting cylinder is
placed in the open to catch rain and the quantity recorded.
There are also 130 automatic rain gauges, which enable Agency
staff to record not only how much rain is falling, but also when
the rain is falling. Although there are local and annual variations,
the average rainfall across the region is 595 mm per year (the
lowest in the country).
A gauging station
• How do you think we can conserve
water at home or at school? Make
a list putting the most practical
ideas at the top.
Activities
• Design a poster which would
encourage you and your friends
save water in the home.
The volume or amount of water flowing down a river (called
discharge) can be measured and calculated manually, but there
are also 200 gauging stations. These automatic sensors
continuously record the level of water in rivers and estuaries.
Discharge is also measured manually once a month at 350 sites.
• Measuring groundwater
The amount of underground water is measured at 1,300
boreholes, indicating the level of water in the aquifer. By plotting
the results on a graph it is possible to see long term trends in the
amount of groundwater. Levels of water in both rivers and
aquifers fall in the summer months when evaporation is high
(because warm temperatures increase evaporation) but rise as
they are recharged in the winter months.
• Design and make a rain gauge,
and use it to determine the weekly
rainfall in your garden. Try doing
the same at school and compare
the figures with class-mates from
different areas.
If there is a period of heavy rainfall, it does not mean that there
will immediately be a flood. There is a time lag, as it takes time
for the water to runoff the land into rivers, or to soak into the
ground filling the aquifer.
• Try designing a garden which
conserves water. What type of
plants should you plant? What
other considerations should there
be? Can you avoid using a
hosepipe in your garden?
The Environment Agency tries to make sure the future supply of
water can meet demand. This is called Demand Management
and includes:
Have you seen our Web Site?
www.environment-agency.gov.uk
www.environment-agency.wales.gov.uk
Other education factsheets in the series:-
1. RIVER FLOODING
2. COASTAL FLOODING
3. THE WATER CYCLE
4. POLLUTION
5. WASTE CONTROL
6. USES OF THE WATER
ENVIRONMENT
7. ENVIRONMENTAL
MANAGEMENT
8. CONSERVATION
This Factsheet may be copied for
educational purposes
FUTURE POLICY
• Making people more aware of how wastage can be
prevented and encouraging them to report leaks and
unnecessary use of water. For example, a garden hosepipe
can use 220 gallons per hour.
• Using water more wisely can also help protect supplies. For
example, if farmers irrigate their crops in the evening when
it is cooler, loss of water through evaporation is reduced.
Protecting the amount of water in rivers and aquifers is also
achieved through restricting the amount of water allowed to be
taken by the water companies, farmers and industry. Taking
water from rivers lakes or aquifers is called abstraction. The
Agency issues licences allowing people to abstract water from
rivers and underground supplies. This limits the amount of water
that can be taken, and protects the resource from overuse. This is
called Resource Management. Discharge from rivers can also be
maintained by transferring water from one area to another.
Published by the Public Relations
Department of the Environment
Agency, Anglian Region,
Kingfisher House, Orton Goldhay,
Peterborough PE2 5ZR.
Telephone (01733) 371811.
P143
• Why do you think there is such a
big difference between the
average water consumption in
Gambia and the UK?
• River levels and flow
AN-3/99-5K-D-A5YV Printed on Cyclus - a 100% recycled TCF paper
Questions