The world’s water
Water quality and the availability of freshwater resources are two of the major environmental issues confronting humanity today. In a way, they can be considered as the single most important issue since water related problems affect the lives of several million people. In the coming years, difficulties relating to water shortages will effectively concern everyone and enormous sums of money will have to be invested in water management. Despite this effort, it will be difficult to improve the situation of 33% of the total world population who do not have access to water, and some 50% of whom lack basic sanitary conditions.
This ‘hydric stress’ already affects 1.7 billion individuals and could affect 5 billion individuals by 2025. Floods and drought kill more people and create more environment damage than any other form of natural catastrophe. The international community is currently combining efforts to improve water management and distribution around the world to ensure a secure future for those populations threatened by the scarcity of freshwater.
|1 • evaporation
7 underground drainage
Water is a natural resource vital to plant, animal and human life. All
life is impossible without it as it regulates the metabolism
of every living organism. 70% of the world’s surface is covered with
water but only 3% is freshwater of which 79% is in the form of polar ice
and 20% exists as inaccessible underground sources. Only 1% is easily available
from rivers, lakes and wells.
Under the impact of solar energy, water in lakes and oceans evaporates to the atmosphere in the form of water vapour. When the temperature drops, water vapour condenses and forms clouds, if the temperature drops still further, then the water contained in the clouds falls to earth as rain. Surface water in lakes, rivers and underground reserves originate from this rainfall. Surface or underground water sources finally rejoin the seas and oceans, thereby completing the cycle.
Water availability influences domestic life as well as the development of pastoralism or certain agricultural techniques. In drylands more than anywhere else, the availability of water is a vital requirement. These areas are characterized by a high rate of evaporation, and surface waters (rivers, lakes) generally tended to disappear relatively quickly. People therefore had to develop different ways to access underground sources (aquifers) to re-route the flow toward areas that require it, particularly the oaes. Rainwater penetrates the earth as it flows and replenishes the underground reserves, the presence of trees, bushes and other plants help limit water loss (run-off).
People have invented diverse solutions to access, use and distribute water; they include the following:
4. Douguia in Chad: a water pump at a local school.
In certain regions of the world, freshwater is abundant
and is consumed in large quantities, however, in other
regions, the slighest water drop is treated as precious.
© Amélie Dupuy
Due to human activities, water use is continually rising and varies considerably in different countries according to lifestyles and water availability:
• Industrialized countries use on average
300 litres/per person/day, according to their lifestyle
• Developing countries consume a lot less water, between 10 to 30 litres/pp/day
Water scarcity and poor water quality threatens public health, food and energy production and the regional economy. It is estimated that 40% of the world’s population (80 countries) suffer water shortages. In the drylands, pratically all water reserves are utilized and are often threatened with dessication or pollution.
To be fit for consumption (potable), water should be transparent, should
not contain soil/earth or silt in suspension and should not be polluted.
Pollution has diverse origins: chemical substances (salts, metals, diverse
minerals), agricultural and human waste (fertilizer, pesticides,
manure, dung, washing water), bacteria, diverse larvae, etc.
Water can also be an agent for the spread of numerous diseases such as typhoid, poliomyelitis, dysentery and cholera.
In hot countries where high temperatures encourage germ proliferation, it is recommended to boil water to kill germs, rendering it fit for drinking and food preparation. The inaccessibilty and scarcity of potable water are important causes of mortality in developing countries: less than 50% of the population have ready access to potable water. Diseases related to water quality account for the death of almost
13 million people a year of which 5 million children die every year from dysentery.
the class divides up into several teams. Each team receives a receptacle filled to the top with water. The receptacle should be of the same size.
One after the other, your team-mates have to carry the receptacle across a predefined obstacle course, spilling as little as possible.
The team who has spilled the least is pronounced the winner.
Do you know of ways to save water, maybe at home? Describe the techniques and add them to your notebook, then share them with your classmates.
The best of them will be noted on a sheet of paper and pasted to the wall chart.
Place several large receptacles outdoors to collect water during the rainy season. Measure the quantity of rainwater daily.
What do you think the rainwater could be used for?
Discuss this in class.
Set up a water assembly in your class. Designate roles among yourselves, some will play the role of the villagers, others could be the water deciders.
The water ‘master’ calculates the daily consumption of water for drinking, washing, cleaning, gardening etc.
The different actors devise together techniques for reducing water consumption.
Measure the quantity of water used in your home on a daily basis. Ask one of your parents to help you.
Compare your results with those of your classmates.