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Chapter 4: Water Supply- Will our taps run dry? (Credits (What is water…
Chapter 4: Water Supply- Will our taps run dry? 
Global Distribution of Water
Oceans
The world's oceans are all interconnected in a single,enormous body of water
This is divided into five oceans,according to the continents they are close to
Pacific Ocean (155,557,000 sq km)(located between the Southern Ocean, Asia and Australia and the Western Hemisphere)
Atlantic Ocean (76,762,000 sq km)(located between Africa, Europe, the Southern Ocean and the Western Hemisphere)
Indian Ocean (68,566,000 sq km)(located between Africa, the Southern Ocean, Asia and Australia)
Southern Ocean (20,327,000 sq km)(extends from the coast of Antarctica to 60 degrees south latitude)
Arctic Ocean (14,056,000 sq km)(extends between Europe, Asia and North America and most of its waters are north of the Arctic Circle)
The Pacific Ocean is the largest,covering about one-third of the total area of the earth's surface
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Groundwater
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Ice caps,glaciers,rivers and lakes
Introduction
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An ice cap is thick,continuous mass of ice which covers large areas of land
A glacier is a body of ice that moves down a slope due to gravity.Glacier form when snow accumulates and and is compacted to form ice.The size of glaciers can range from a football field to a river 160 km long.
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A river is a large natural stream of fresh water flowing along a definite course into another water body
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River
As the river flows downstream,precipitation,groundwater and other smaller streams add to the flow
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Together,a river and its tributaries make up a river system
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At the mouth,the river flows into another body of water such as a lake or the ocean
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The source of a river may be a lake,a spring or a melting glacier
Lake
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The Great Lakes of North America is the largest group of freshwater lakes on earth,consisting...
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Introduction
Water
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However,most of the earth's water is in the ocean,which is too salty to use or drink
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In fact,about 71% of the earth's surface is covered with water
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What is water shortage?
The hydrological cycle
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It refers to the continuous movement of water from the earth surface to the atmosphere and back again
Along the way,the water takes on different states (solid,liquid or gas)
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The hydrological cycle:
1.Evaporation........................................................................................................................Heat from the sun causes water from lakes,rivers,oceans and the surface layers of soil to change to water vapour.This process is called evaporation.Plants also give out water vapour through their leaves in a process known as transpiration
2.Condensation.......................................................................................As the water vapour rise into the atmosphere,it cools.At cooler temperatures,water vapour becomes water droplets through condensation
3.Precipitation..........................................................................................These water droplets gather together to form clouds.When more water droplets gather,the clouds get too heavy.Thus,water falls back to the earth's surface in a process called precipitation.Precipitation includes all forms of water such as rain and snow
4.Infiltration and groundwater flow....................................................... Some of the water that falls onto the ground may seep into the soil.This process is called infiltration.Water that infiltrates deep into the ground,and is contained in the soil and the underlying rocks,becomes groundwater.
5.Surface runoff......................................................................................................... The rest of the water that is not absorbed into the ground flows over earth's surface,down hills and mountains into rivers,lakes and eventually seas.This water is known as surface runoff
Uses of water
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Water footprint
What is water footprint?
Water footprint refers to the total volume of water (in cubic metres) used to produce the goods and services for a person in a year. This includes all domestic and economic uses of water
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Water shortage
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Example: New Delhi,a city in India
Residents in New Delhi,a city in india,was facing water shortage due to the country's growing population
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According to official estimates,New Delhi's water demand in the peak summer months has reached more than 4.35 million cubic metres a day. However,the city is getting only about 3.22 million cubic metres a day
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Which locations in the world are facing water shortage?
Introduction
As fresh water is distributed unevenly across the world,the amount of fresh water available per capita can vary tremendously around the world
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Why does water shortage occur?
Demand factors
Population growth
Introduction,world population
The world population grew from 1.6 billion in 1990 to 3.1 billion in 1960.This increased by almost two times to 6.1 billion in 2000
As world population grows at at an increasing rate,so does the need or water.Water consumption for agricultural will thus increase
Production of animal products is extremely water-intensive.Beef production uses a large amount of water to grow the grain needed to feed cattle
Worldwide demand for water is doubling every 21 years,or faster in some countries.Water supply cannot keep up with such demands
1900=~16.667(3 d.p.) km3/billion people (~1.5 billion people,25 km3 per year) 2010=~35.714(3 d.p.) km3/billion people (~7 billion people,250 km3 per year) Difference=~19.047 (3 d.p.) km3/billion people (5.5 billions people,225 km3 per year)
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Example: Most of the world's population growth take place in less developed countries,mostly Asia and Africa.
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Affluence
Introduction
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Affluent countries are usually developed countries such as the United States of America,Europe,Japan and Australia
People living in these countries use more water than those in less developed countries (e.g. India,China,Vietnam).
In other words,developed countries have a greater water footprint
Water consumption has increased twice as fast as population growth in the last century because of affluence
For example,the United States of America has an enormous water footprint that is more than double that of Vietnam.
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With more money,people may also start to consume goods that are produced using more water and live a lifestyle that consumes more water
Water used for ornamental and leisure purposes Water is used for ornamental purposes such as fountains and leisure purposes such as swimming pools.Much of this water,however,is lost via evaporation or leakage
Piped water Millions of people worldwide will change their water source from the village well to piped water for showers and flush toilets
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More water-intensive appliances used People can afford water-intensive appliances such as washing machines and dishwashers.
More goods purchased People can spend more on goods such as clothing.The textile industry is one that uses a lot of water.For example,manufacturing one cotton T-shirt requires 400L of water
Between 2007 and 2025,water consumption is predicted to rise by 50% in less developed countries and 18% in developed countries.Much of the increase come from the poorest countries as more and more people move from rural areas to cities.
Supply factors
Seasonal rainfall
Introduction
In some countries,however,rainfall can vary greatly from month to month.This affects the supply of fresh water available for use.
In Singapore,the amount of rainfall is generally the same every month and the annual percipitation is more than 2000mm
Although India has a high annual precipitation of more than 1200mm,its rainfall is unevenly distributed throughout the year
Most rainfall is received between June and September during the southwest monsoon season,leaving the rest of the year dry
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Example: India
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In 2009,the monsoon rains did not come on time,leading to widespread drought.The drought caused sugar production to be so low that India had to import sugar
In 2012,the monsoon rains were below average in the first half of the season,causing large parts of the country to experience drought.City such as New Delhi faced water shortage.The heavy rains eventually came in August but it was too late for many rain-dependent farms
With more than half of India's population engaged in the farming ,the timing and amount of rainfall are crucial for the harvesting of crops
Climate Change
Irregular distribution of rainfall throughout the year in some regions will be intensified by climate change
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In recent years,the earth's average temperature is predicted to rise due to the increase in greenhouse gases in the atmosphere.This is also known as global warming.Green house gases trap heat.
This increase in temperature will cause a change in rainfall patterns and more extreme weather-related hazards such as floods and drought.
If nothing is done,it is predicted that the severe droughts now occurring once every 50 years could occur every second year by 2100
Water pollution
Introduction
Pollution is the introduction of substances into the natural environment(air,water,land) that results in unpleasant or damaging effects to the environment and human health
Some common pollutants include garbage,chemicals and waste water
These can come from agricultural,industrial and other human activities
Houses: Oil,grease,litter,soap, and anything else that goes down the drain are all washed into the river
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Example: The Ganges River,the largest river in India
Introduction
More than 400 million people live along the river,making it the most populated river basin in the world
The river provides water for drinking,bathing and irrigation.It also holds spiritual significance as it is seen as a sacred river
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Pollution
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Most of the industries near the river have inadequate waste treatment facilities and dump their waste directly into the river
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In many places,water shortage is caused by both natural and human factors.As a result,many people spend a large proportion of their time searching for clean water.There are serious consequences to lacking such an essential and precious resource
Introduction
Through the hydrological cycle,our precious water resource is continually replenished
However,with the growing demand for water,there is more pressure on this resource than ever before
More and more water is needed to meet the needs of growing population and people who are adopting more affluent lifestyles
At the same time,water supply can decrease due to pollution and the uncertainty of seasonal rainfall
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