2. OUTLINES OF LECTURE
⚫Introduction.
⚫ Water on and in the Earth Accessible Fresh
Water.
⚫ How much of Earth's water is available for
our uses.
⚫Water Purposes.
⚫Water Cycle.
⚫Sources of water.
⚫Water pollution.
3. Introduction
Water is a basic natural resource required by all human
beings. On a global scale, 1.1 billion people do not have
access to safe drinking water. 80 percent of all illnesses
in developing countries are attributed to unsafe
drinking water and the spread of waterborne diseases.
There are 2.2 million deaths each year that result from
unsafe drinking water, 90 percent of whom are
children under five years of age. Man requires a
minimum body intake of water that varies from 2.8 - 13
liters per day depending on the climate and the
temperature. The water is normally taken in food and
drink, and the intake must balance the water loss from
the body.
4. If there is no intake of water into the body, death can
ensue in 7-10 days. Water is also essential to man for
maintaining personal hygiene and freedom from
disease.
Tounderstand water, we must understand its
characteristics, and roles:
Water has a high capacity to absorb and store heat.
Water is the universal solvent.
Water has a high surface tension.
Water is the onlycompound whose solid form is
lighter than its liquid form.
Sunlight penetrates water to variable depths,
permitting photosynthetic organisms to live below
the surface.
5. Wateris essential to life and a nominal supplyof
clean-safe drinking water is required for the
sustenance of life. Concern regarding safe-clean
drinking watercommenced atthe turn of the
21th century,of the total volumeof water 70.8 %
on the planetearth, the human bodyabout 70
%. Mostof the water97% found as salt water
(Oceansand seas), theotheras freshwaterabout
3 %. The fresh wateravailableasannual stream
flow is 0.00034% of the total global water.
8. By viewing these pie charts above, we can see how water
is distributed. The left-side pie shows where the water
on Earth exists; about 97 percent of all water is in the
oceans. The chart shows the distribution of that three
percent of all Earth's water that is freshwater. The
majority, about 69 percent, is locked up in glaciers and
icecaps, mainly in Greenland and Antarctica. You might
be surprised that of the remaining freshwater, almost
all of it as ground water, the ground below you is
saturated with water. Of all the freshwater on Earth,
only about 0.3 percent is contained in rivers and lakes—
yet rivers and lakes are not only the water we are most
familiar with, it is also where most of the water we use in
our everyday lives exists.
9. How much of Earth's water is available for our uses
What forms does it exist? You can best see how water is
distributed by viewing these pie charts. The right-side
pie chart shows that over 99 percent of all water
(oceans, seas, ice, most saline water, and atmospheric
water) is not available for our uses. And even of the
remaining fraction of one percent (the small blue slice
in the top pie chart), much of that is out of reach.
Considering that most of the water we use in everyday
life comes from rivers (the small dark blue slice in the
pie chart), you'll see we generally only make use of a
tiny portion of the available water supplies. The pie
shows that the vast majority of the fresh water available
for our uses is stored in the ground (the large grey slice
in the second pie chart).
10. WATER PURPOSES
In addition to personal use, water is required for many
other purposes namely:
1. Public water supplies- Most of these supplies are
used by domestic households for drinking, cooking,
dishwashing, general cleaning, laundry, personal
washing and bathing, lavatory f lushing, car washing
and garden watering.
2. Industrial
processes
treatment
water Supplies - Various industrial
require large quantities of water for
purposes, steam raising, material
processing and the disposal of waste.
11. WATER PURPOSES
3.Cooling water is used in large quantities for the
generation of electricity.
Thiswater is usuallyobtained from rivers, lakesand rivers.
4.Water for Agricultural purposes –The agricultural uses
comparatively large quantities of water for dairy processing,
animal hygiene. The Horticultural industry uses water for
land irrigation, glasshouse watering and marketable
vegetable.
5.Water for amenity and recreational purposes. This
includes streams, rivers, reservoirs, estuaries, canals, and
coastal waters. This water is used for all types of water
sports such as swimming, fishing, boating, sailing, skiing as
a means of transport forpleasureor Commercial purposes.
12. Water Cycle
Water never leaves the Earth. It is constantly being
cycled through the atmosphere, ocean, and land. This
process, known as the water cycle, is driven by
energy from the sun. The water cycle is crucial to the
existence of life on our planet.
During part of the water cycle, the sun heats up liquid
water and changes it to a gas by the process of
evaporation. Water that evaporates from Earth’s oceans,
lakes, rivers, and moist soil rises up into the
of evaporation from plants is
(In other words, it’s like
called
plants
atmosphere.
The process
transpiration.
sweating.)
13. As water (in the form of gas) rises higher in the atmosphere, it
starts to cool and become a liquid again. This process is called
condensation. When a large amount of water vapor
condenses, it results in the formation of clouds.
When the water in the clouds gets too heavy, the water falls
back to the earth. This is called precipitation.
When rain falls on the land, some of the water is absorbed
into the ground forming pockets of water called groundwater.
Most groundwater eventually returns to the ocean. Other
precipitation runs directly into streams or rivers. Water that
collects in rivers, streams, and oceans is called runoff.
The input to the hydrological cycle on land is precipitated
water falling as rain, hail or snow. When this water reaches the
ground some of it is evaporated, or runs off into the sea,
streams and rivers, and the remaining enters the ground water
system.
14.
15. Sources of water
Man obtainswaterfromtwochief sourcesof supply:
1. Surface water- this is drawn from streams, rivers, lakes and
storage reservoirsexample (Household tanks).
Surfacewater,especiallyin rivers has threefunctions.
Riversprovidea sourceof waterforall users,
They are also used for the removal of effluent discharges from
industrial plants and sewage works (only after crucial
treatment).
Rivers also have a recreational and amenity role in providing
facilities for fishing, swimming, boating and sailing in the
countryside and towns. If the rivers ecosystem is polluted then,
the recreationaland amenityfunctionsarediminished.
The quality of surface water, the degree of pollution present,
and fluctuations in the volume of water available are crucial
factors that determine the volume of water supplies available
forall users.
16. Sources of water
2. Ground water – This is drawn from underground aquifers
through boreholes and wells.
Aquifers or water bearing rock layers (ground water) can be
used as an alternative to surface water. Aquifers provide a
natural storage for ground water, and they exist in rock strata
such as sandstone, some limestones and chalk, sited above
impermeable rock. Water is abstracted by wells or bore-holes,
and it is replenished by ground water infiltrating from around
the wateraquifer. Aquiferscan be polluted in two ways:
(i) If they are sited in coastal areas where the porous rock is
below sea level, there may be an intrusion of sea water, when
the level of fresh water falls below a critical point in theaquifer.
(ii)Pollution can occur if an aquifer is supplied by ground water
that has percolated through polluted ground or a land tip.
17. WATER POLLUTION
Definition:
- Water pollution is the contamination of water bodies
(e.g. lakes, rivers, oceans, aquifers and groundwater).
This form of environmental degradation occurs when
pollutants are directly or indirectly discharged into
water bodies without adequate treatment to remove
harmful compounds.
- Basically water pollution is induced by human
activities which cause pollutants to enter natural
waters.
18. -To the general public, pollution is evident in terms of
the observed appearance of the water eg. A river is
polluted if the water is turbid, has foam on the
surface, has an objectionable smell, and does not
support fish and other living organisms.
Water pollution is a major global problem that
requires ongoing evaluation and revision of water
resource policy at all levels (from international down
to individual aquifers and wells). It has been
suggested that it is the leading worldwide cause of
deaths and diseases, and that it accounts for the
deaths of people daily.
19. In addition to the acute problems of water pollution
in developing countries, industrialized countries
continue to struggle with pollution problems as well.
Water is typically referred to as polluted when it is
impaired by anthropogenic contaminants and either
does not support a human use, such as drinking
water, and/or undergoes a marked shift in its ability to
support its constituent biotic communities, such as
fish.
20. Natural phenomena such as volcanoes, algae blooms,
storms, and earthquakes also cause major changes in
water quality and the ecological status of water. Most
water pollutants are eventually carried by rivers into
the oceans. In some areas of the world, the influence
can be traced up to one hundred miles from the
mouth by studies using hydrology transport models.
21. The specific contaminants leading
water include a wide spectrum
to pollution in
of chemicals,
pathogens, and physical or sensory changes, such as
elevated temperature and discoloration. While many
of the chemicals and substances that are regulated
maybe naturally occurring (calcium, sodium, iron,
manganese, etc.), the concentration is often the key in
determining what is a natural component of water,
and what is a contaminant. High concentrations of
naturally-occurring substances can have negative
impacts on aquatic flora and fauna. Oxygen-depleting
substances may be natural materials, such as plant
matter (e.g. leaves and grass) as well as man-made
chemicals.
22. Other natural and anthropogenic substances may
cause turbidity (cloudiness) which blocks light and
disrupts plant growth, clogging the gills of some fish
species. Many of the chemical substances are toxic.
Pathogens can produce waterborne diseases in either
human or animal hosts. Alteration of water's physical
chemistry includes acidity(change in pH), electrical
conductivity, temperature, and eutrophication.
Eutrophication is an increase in the concentration of
chemical nutrients in an ecosystem to an extent that
increases in the primary productivity of the
ecosystem.
23. Depending on the degree of eutrophication,
subsequent negative environmental effects such as
anoxia (oxygen depletion) and severe reductions in
water quality may occur, affecting fish and other
animal populations.
Water is a unique substance, because it can naturally
renew and cleanse itself, by allowing pollutants to
settle out (through the process of sedimentation) or
break down, or by diluting the pollutants to a point
where they are not in harmful concentrations.
24. However,
difficult
this natural process takes time, and is
when excessive quantities of harmful
contaminants are added to the water. And humans are
using more and more materials that are polluting the
water sources that we drink from. The list of
pollutants is long and the signs of water pollution
surround us, but the point is this: we are dumping
contaminants into the small portion of water on the
planet that is fit fordrinking.
