3. Learning Objectives
At the end of the lesson, you should be able to:
1.Understand the causes and effects of water pollution;
2.Identify major water pollution problems in streams and
lakes;
3.Identify major pollution problems affecting
groundwater and other drinking water sources
4.Understand the major water pollution problems
affecting oceans; and,
5.Think of ways how to best deal with water pollution.
4. Water
• Plays a key role in determining the earth’s
climates
• 71% of Earth’s surface is saltwater
• Removes and dilutes some of the pollutants
and wastes that we produce
• Sculpts the planet’s surface, creating
valleys, canyons, and other land features.
7. Freshwater
• Contains very low levels of dissolved salts - -
- less than about 500 ppm (0.05%).
• One of our most poorly managed resources
8. Water Access
• Global Health Issue – 4,100 people/day die from
waterborne infectious diseases
• Economic Issue – 52% of the world’s people
have water piped to their homes.
• National and Global Issue – increasing tensions
within and between nations over access to
limited freshwater resources
• Environmental Issue – excessive withdrawal of
freshwater from rivers and aquifers has resulted
in falling water tables, dwindling river flows,
among others.
9. Earth’s Water Composition
• 0.024% - readily available to us as liquid
freshwater stored in accessible underground
deposits and in lakes.
• 96.5% - salty oceans
• 1.7% - frozen polar ice caps and glaciers
10. Groundwater
• The freshwater in underground spaces
• Zone of saturation – depth where spaces are
completely filled with freshwater.
• Water Table – on the top of groundwater zone,
and falls in dry weather or when we remove
groundwater from the zone faster than nature
can replenish it.
• Aquifers – deeper down geological layers, like
large elongated sponges where groundwater
seeps through porous layers
• Most aquifers are replenished, or recharged,
naturally by precipitation that sinks downward
through exposed soil and rock.
13. Aquifer
• Most aquifers are renewable resources
unless the groundwater they contain
becomes contaminated or is removed faster
than it is replenished.
• Aquifers provide drinking water for nearly
half of the world’s people
14. Aquifers
• Deep aquifers – aka fossil aquifers,
were filled with water by glaciers that
melted thousands of years ago.
• These are nonrenewable
15.
16. Surface Water
• The freshwater from rain and melted snow
that flows or is stored in lakes, reservoirs,
wetlands, streams, and rivers.
• Surface runoff – precipitation that does not
soak into the ground or return to the
atmosphere by evaporation
• Watershed or drainage basin – the land
from which surface runoff drains into a
particular stream, lake, wetland or other
body of water.
17.
18. Scarcity
• Freshwater scarcity stress – it is a measure based
on the amount of freshwater available compared
to the amount used for human purposes.
• By 2050, some 60 countries, many of them in
Asia, with ¾ of the world’s population, are likely
to be suffering from such freshwater scarcity
stress.
• By 2059, 45% of the earth’s land surface could
experience higher level of drought called extreme
drought.
19. Extracting Groundwater
• Test wells and satellite data indicate that water
tables are falling in may areas of the world
• The rate at which water is being pumped out of
most of the world’s aquifers (mostly to irrigate
crops) is greater than the rate of natural
recharge from rainfall and snowmelt.
22. Overpumping Aquifers
• Overpumping aquifers contributes to limits on
food production, rising food prices, and widening
gaps between the rich and poor in some areas.
• It will then lead to rising hunger and social unrest.
• Withdrawing large amounts of groundwater
sometimes causes the sand and rock to collapse,
resulting to land subsidence.
23. Dams
A dam is a structure built across a river to control its
flow.
Reservoir – artificial lake created behind the dam.
24. Purpose of Dams
The purpose of a dam-and-reservoir system is to
capture and store the surface runoff from a river’s
watershed, and release it as needed to control floods,
to generate electricity (hydropower), and to supply
freshwater for irrigation and for towns and cities.
25. Drawbacks
This engineering approach to river management
has displaced 40 million to 80 million people from their
homes and impaired some of the important ecosystem
services that rivers provide.
28. Water Transfer
In some heavily populated dry areas of the world,
governments have tried to solve water shortage
problems by transferring water from water-rich areas
to waterpoor areas.
29.
30.
31. Conversion of Salt Water
to Freshwater
Desalination is the process of removing dissolved
salts from ocean water or from brackish(slightly salty)
water in aquifers or lakes.
- Distillation – heating salt water until evaporation
- Reverse Osmosis – forcing saltwater through a
membrane filter with pores
34. Major Problems of
Desalination
▪ High Cost
▪ Use of Chemicals kills marine organisms
▪ Produces huge quantities of salty
wastewater
35. Major Problems of
Desalination
▪ High Cost
▪ Use of Chemicals kills marine organisms
▪ Produces huge quantities of salty
wastewater
36. Flooding
A flood happens when freshwater in a
stream overflows its normal channel and
spills into the adjacent are, called the
floodplain.
- Removal of water-absorbing vegetation
- Draining of wetlands
