1. Two-thirds of the earth's Surface is covered with seas and oceans. But how much of the world's water is suitable for human use?
Only about 2.5 per cent of the water is fresh water. The rest is salt water. However, most of the fresh water is held in glaciers and polar icecaps or locked in deep aquifers, thus not available for human use. The result is that only about 0.25 per cent of the world's water, mostly in rivers, lakes and shallow aquifers, can be used to meet human needs.
2. Which human activity uses the most water?
70 per cent of all water is used for irrigation: half of that is lost through infiltration into the soil and evaporation into the air.
3. How much water does one city-dweller use per day just by taking a shower, flushing the toilet, washing dishes and clothes, etc.?
At the lower end, the city of Hong Kong, China may serve as an example: average daily consumption is about 112 liters per day, per person. At the high end, we can take the example of Bangkok, where average consumption is about 265 liters per day, per person. Only 2 to 5 liters of drinking water are needed per person for daily physiological needs.
4. Guess how much water is used for your daily shower, for a nice bath, and for a toilet flush.
The average shower takes between 50 and 100 liters. A nice bath takes at least 200 liters. A toilet flush takes 5 to 15 liters, depending on the model of toilet.
5. How many tanker trucks would be needed to bring and take away water sufficient for a town of about 10,000 inhabitants?
In our fictive example, each day a convoy of 150 tanker trucks (a queue 3 km long) would be needed to bring the water and again in the water and again in the evening to take away the dirty water.
6. Imagine your tap is leaking drop after drop. How much water is lost from this leaking tap per day?
A leaking tap can lose up to 100 liters per day, which is the equivalent of about eight buckets of water. If the tap keeps dripping over one year, about 35,000 liters of clean fresh water will be lost.
7. What is the estimated number of people globally without access to a safe water supply and modern sanitation facilities?
At the end of 1999, about one billion people lacked access to a safe drinking water supply, while over 2.4 billion people did not enjoy access to modern sanitation facilities. This constitutes over one third of the world's population.
8. How many infant deaths a year in the Asia and Pacific region are caused by contaminated water and poor sanitation?
More than 500,000, together with illness and disability. According to the World Health Organization, diarrhea associated with contaminated water poses the most serious threat to health in the region and about 40 per cent of the total global diarrhea episodes in under-fives during 1990 occurred in the region.
9. How many liters of water are needed to grow on kilogram of chicken and beef?
Rice needs about 1,900 liters. Rice is the most thirsty grain crop. One kilogram of chicken needs 3,500 liters of water, and one kilogram of beef needs a staggering 100,000 liters of water. The animals themselves drink little of this water - most of it used to grow their feed.
10. How many liters of water are needed to make one liter of beer, one kilogram of wool, and one kilogram of paper?
Brewing a litter of beer takes an average of 25 liters, producing a kilogram of wool takes 150 liters, and making a kilogram of paper takes an average of 300 liters of water.