Water

Introduction

Water is one of the basic substance present in the earth. It plays a vital role in the evolution and survival of life. It is impossible to imagine life on the earth without water. Water helps to regulate the temperature of our planet. It also helps to maintain the temperature in organisms.

Where and how water is found on the earth?

Water is available in nature in three forms – Solid, Liquid , Vapour.

Ø Solid form of water - Ice - It is present in ice bergs and ice caps on top of tall mountains, galaciers and polar regions.

Ø Liquid form of water – Water – It is present in oceans, seas, lakes, rivers and even underground.

Ø Gaseous form of water – Vapour – It is present in the air around us.

Availability of water

We know that nearly ¾th of the surface of the earth is covered by water. Most of the water, that is 97% of the total amount of water that exits on earth is found in seas and oceans. Can we drink the water available in the sea? Sea water is salty. But water used for our daily purposes is not salty. It is known as fresh water. Water obtained from ponds, puddles, river, tube-wells and taps at home is usually fresh water. If the total water on earth be 100%, let’s see what percent would be the availability of fresh water. Look at the pie chart given below

From the pie chart, it can also be noted that 97% water is saline water. Only 3% found is the freshwater and that too in polar ice caps and glaciers. So this portion of water is not readily available for drinking.

The distribution of the totally available freshwater is as follows:

· Polar ice caps and glaciers 68.7%

· Ground water 30.1%

· Other sources of water 0.9%

· Surface water 0.3 %

The distribution of total surface water is as follows:

· Lakes 87%

· Rivers 2%

· Swamps 11%

Thus the above pie chart explains that we have a very small amount of fresh water available for human usage and so maintaining the water table and the conservation of water is very essential.

Composition of water

Water is a transparent, tasteless, odourless and nearly colourless chemical substance. It is composed of two atoms of hydrogen combined with one atom of oxygen. The molecular formula of water is H2O. However, the physical composition of water changes from place to place. It can be clear or cloudy, oxygenated or not very oxygenated and it can be fresh or salty. The amount of salt in water is termed as salinity. Based on its salinity water is classified into three main categories such as freshwater, brackish water and sea water. Fresh water contains 0.05% to 1% of salt. Brackish water contains upto 3% of salt and seawater contains more than 3% of salt. Ocean water is composed of many substances. The salts include sodium chloride, magnesium chloride and calcium chloride.

Water cycle

The water on the earth evaporates into the atmosphere due to the heat of the sun. The water vapour in the atmosphere forms clouds. From the clouds water falls on the earth in the form of rain or snow. By this natural process, water gets renewed. This is called water cycle. Water cycle is a continuous process. It involves three stages - evaporation, condensation and precipitation. It is also called the hydrological cycle. Evaporation : Water from oceans, lakes,ponds and rivers evaporates due to the heat of the sun. Condensation : Water vapour which enters into the atmosphere by evaporation moves upward with air, gets cooled and changes into tiny water droplets that form clouds in the sky

Precipitation : The millions of tiny droplets collide with one another to form larger droplets. When the air around the clouds is cool these drops of water fall in the form of snow or rain.

Natural Sources of fresh water

Three types of natural sources of fresh water are available on the earth.

v Surface water

Water present on the surface of the earth such as river,lake,ponds, streams or fresh water wetland is called surface water.

v Frozen water

Water that is present in the frozen form as polar ice-caps and glaciers are called frozen water. A larger portion of water is 68.7% of the total available fresh water is in frozen state.

v Ground water

Ground water is the water present beneath Earth's surface in soil. This water is obtained through springs, open wells, tube wells, or hand pumps etc.,

Conservation of water

There is no change in the total quantity of water available on the earth. It remains the same. But the water useful for plants, animals and man is decreasing day by day. It is called scarcity of water.

The main reasons for water scarcity

· Population explosion

· Uneven distribution of rainfall

· Decline of ground watertable

· Pollution of water

· Careless use of water

Methods of water conservation:

Mainly, two methods can be followed for the conservation of water.

Ø Water management

· Bringing awareness about the bad effects of throwing wastes into the water bodies

· Recycling of water by separating pollutants.

· Minimizing the use of chemical fertilizers in agriculture. It reduces the pollution of underground water.

· Controlling deforestation

· Adopting drip irrigation and sprinkler irrigation in agriculture. By this way lesser amount of water can be used for the irrigation

Ø Rainwater harvesting

· Collecting water from where it falls.

(e.g): Collecting water from the roof tops of the houses or buildings (Roof water harvesting).

· Collecting flowing rain water

(e.g): Collecting rainwater by constructing ponds with bund.

Importance of water

Ø Human body

Our body uses water in all its cells, organs and tissues to help regulate its temperature and maintain other bodily functions. On an average, the human body requires 2 – 3 litres of water per day for proper functioning. Water helps in digestion of food and removal of toxins from the body.

Ø Domestic

Apart from drinking, people use water for many other purposes. These include: cooking, bathing, washing clothes, washing utensils, keeping houses and common places clean, watering plants, etc.

Ø Agriculture

Water is also essential for the healthy growth of farm crops and farm stock and is used in the manufacture of many products.

Ø Industry

Industry depends on water at all levels of production. It is used as a material, a solvent and for generating electricity.