Seventy- five percent of the planet is covered by oceans, seas, lakes, swamps and this fact makes the earth watery planet on Earth. There is also frozen water in the polar ice caps and mountains and only 1% of the water is suitable for human needs. Ninety seven percent is salt water in the oceans and 2% is ice.
Water in details
For water to be regarded as pure it must comprise of various elements. Water must be colourless, odourless and tasteless. The water we find in our environment generally has a bluish tint which can only be detected at layers of considerable depth. Rivers often look green or brown because of the sand or mud in them.
Pure water is made up of hydrogen (two elements) and oxygen (one element) making the total of H2O. These two invisible gases combine to form a liquid or solid substance we can see. While they remain in gaseous form such as steam or water vapour they are not always visible. This automatically implies that water can be in form of three forms;
1. Solid e.g. ice, hail, snow or frost (when frozen into ice at O degrees Celsius.)
2. liquid e.g. oceans, rains, clouds, mist, tap water, or dew
3. gas e.g. steam, air or water vapour
Water is liquid only over a narrow temperature ranging between O degrees Celsius and 100 degrees Celsius. This means if the earth was just a little closer to the sun most of the water would turn into water vapour and if it was just a little further away most of it would turn into solid substance or ice.
As we have already studied that the planet earth is covered by water it means water is everywhere around us. in the air and in the ground, in the vegetables, fruit, meat, drinks, leaves, trunks, roots, branches of trees, animals and peoples.
The blood, muscles and bones in our body contain a great deal of water. From 50% to 90% of the weight of living things is water. Our bodies are in fact almost 70% of water. The human brain is 75% of water.
Water and our bodies
The average adult loses about 3 to 3.5 litres of water in an average day through the skin, lungs and body wastes. This may be increased by exercise and climate conditions. It is vital to replace the water that our bodies lose and we can only do this by eating and drinking. The average adult should drink a minimum of two litres of water daily.
Water gives us ability to live on earth
As most of the people including me and you switch on their air conditioners inside their houses and cars those outside are naturally air-conditioned by water. Water in the thick layer of air around the earth absorbs the hot rays of the sun; if it were not there, it would be too hot on earth for life. At night it is the opposite. The damp air holds in the heat that has been absorbed during the day. Otherwise the earth would freeze every night. Air is never completely dry; there is always a blanket of moisture around the earth.
Mixing things with water
Water can be mingled with many things. For example we normally mix sugar, salt or maize meal with water. But you can never mix sand or oil with it.
Our planet earth has been recycling water for years and years till today during the process called Hydrological cycle or water cycle. Water cycle consist of different stages as indicated in the diagram, they are:
Evaporation- it occurs when water is heated and altering into water vapour, a gas, and rising into the air, for example lakes, rivers, dams, the ocean and land surfaces.
Transpiration -When water is released into the air by plants.
Condensation-When the water vapour in the air rises it becomes cooler. The cooler the air the less water vapour it can hold and the warmer the air the more it can hold. When the air cannot hold all the water vapour, the excess vapour condenses and turns into tiny droplets of water which appear as fog, mist or clouds.
Precipitation- When the water returns to the earth as rain, hail or snow.
What happens to all the rain that falls from the sky?
Roughly 75% of the water falling from the sky drops into the sea. The remaining 25% falls on the land or into rivers, dams, lakes and swamps.
The water falling on the land can sink into the ground and be absorbed by plants, seep down into the earth’s surface or simply dampen the ground and then quickly evaporates as the sun shines on it.
Sometimes raindrops evaporate before they even reach the ground and start rising up into the sky again as water vapour.
Water in brief
Only 1% of the world’s fresh water is drinkable.
South Africa is the 30th driest country in the world.
South Africa gets, on average, half the rainfall of the rest of the world.
South Africa has the Third cleanest water in the world.
Since 1994 more than 17 million people have gained access to portable water.
About 25 000 litres of water is required to produce food for one day for a family of four.
A dripping tap (one drop per second), wastes up to 30 litres of water an hour. That equals 10 000 litres per year
1 litre of waste water pollutes about 8 litres of fresh water.
Only 50% of water used for irrigation actually reaches the root of the plant.
It takes three litres of water to produce one litre of bottled water; bottled water costs 500 to 1000 times more than tap water.
It takes 7 litres of water to produce 1 litre of petrol.