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Lecture 3

ENVS 1000 Lecture Notes - Lecture 3: Disinfectant, Water Cycle, Aquifer

Environmental Studies
Course Code
ENVS 1000

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Lecture 3
Water (Liquid Natural Capitol)
Water is in the air and in our body (60% of our body)
Earth is a water planet and is 71% percent of it is covered with water
However this water is mostly salt water and this limits its usages and more expensive to use the
limited fresh water.
To convert salt water to drinking water is expensive, corrosive and difficult to do.
No species can exist without water
Water changes the surfaces of the Earth (e.g. hill, valley, canyons) due to erosion of the soil,
rain, weathering
Water moderates climates
It is also used to remove and dilute wastes and pollutants
Human usage: withdrawal total amount of water removed from a river, lake or aquifer for any
purpose. Some of this water can be returned to its source.
o Water cycle is one of the most important cycles on the Earth and reuses and renews
water the supply on Earth
o Humans use 54% of the world’s reliable run-off (surface water). In 2025, humans would
have consumed 70%-90% of available surface water.
o Raises two questions: 1) how much water is available and 2) what is the quality of
available reliable water.
Globally, there is a very low amount of fresh water available. 2.6% of all
available water is fresh water and only 0.14% is readily accessible water.
Some areas of the planet lack a good amount of water (less than 1700 cubic
meters/year/person) (e.g. USA, Africa, and lower Asia). Under water stress.
Canada has 20% of all freshwater in the world.
o Some World’s Problems:
Some areas have a lot of water but the largest rivers are far from agricultural
and population centres. It is very expensive to transport to where it is needed.
Lot of precipitation arrives during short periods which cannot and stored
because it is very expensive
Lakes and rivers are shrinking due to climate change
o How do we use our water?
64% of available water is used for industrial purposes such as power plant
A lot of water is being used in the agricultural centers of the USA, not so much
in Canada. In China, most of the water is used for agriculture purposes (87%).
85% of water available is consumed and not returned to its water basin
In Canada, one household would use for showering (35%) and flushing the
Majority of world lives in hydrological poverty. 1 of 6 people doesn’t have
access to clean water.
Poor quality water can lead to diarrhea and kills 2 million children annually.
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