WATER

IMPORTANT TERMS

Water Table: - The top level of the underground water is called the water table.

Surface Water: - Water present on the surface of the Earth is known as Surface water.

Groundwater: - Water that lies beneath the surface of the Earth is called underground water.

Potable Water: - The water suitable for drinking by living beings is known as potable water.

Transpiration: - The process by which plants give off water vapour through stomata present in leaves.

Epidemic: - The rapid spread of infectious disease to a large number of people within a short period of time.

Drought: - Acute scarcity of water because of absence of rainfall is called drought.

Famine: - Shortage of food in a region for a long period is known as famine.

Melting: - Changing from a solid form to a liquid form is called melting.

Evaporation: - The process by which liquid state changes to a gaseous state due to an increase in temperature.

Freezing: - The process by which water changes phase from a liquid to a solid state.

Flood: - A situation that occurs because of the overflow of water on adjoining land and rivers due to heavy rainfall.

 

WATER AVAILABLE FOR USE

• Water covers about three-fourth (about 71%) of the Earth's surface.

• Approximately 97 percent of the water on Earth is found in the oceans and is salt water. The water in the seas and oceans is so salty that it cannot be used for drinking or other purposes.

• Roughly, a very small fraction (about 3%) of the water found on the Earth is available to us as freshwater. Out of which, 2.997% is frozen in the glaciers and in the polar ice caps and is not readily available. So, the percentage of water available on Earth for use by human beings is about 0.003%.

• About 60% of the population of India depends on agriculture for their living. About 20-22% of water is used by industries and about 8% is used for domestic activities.

 

STATES OF WATER

Water exists in three states or forms: Solid, Liquid and Gas.

• Solid - Below 0 degree Celsius, water remains in solid state. Snow, icebergs, glaciers and hail are solid forms of water.
• Liquid - Water exists mostly in liquid state, between 0°C and 100°C. Dew, rain and water droplets are liquid forms of water.
• Gaseous - Water exists in gaseous state, above 100°C. Water vapour, steam, clouds and fog are gaseous forms of water.

The three states of water are reversible and interchangeable. Water can be converted from one state to another by changing the temperature.

The state of water can be changed by heating the water. When water is heated, it changes into its vapour. The state of water changes from liquid to solid on cooling. The solid form changes to liquid on heating.

 

CLOUD FORMATION

As the temperature of the air increases, it expands, which makes the air lighter. When the moist, warm air moves upwards, it gets cooler and cooler. The air becomes so cool that the water vapour present in it condenses on dust particles to form tiny drops of water. These tiny drops of water hang together in the air. They remain floating in the air and appear as clouds.

 

WATER CYCLE

Water cycle is a continuous circulation of water, wherein water evaporates from the surface of the Earth, form clouds and falls on the surface of Earth as precipitation.

Evaporation - Evaporation is the process in which liquid state changes to a gaseous state due to an increase in temperature. It is a part of the water cycle. During this process, the heat of the sun changes the water in oceans, rivers and other water bodies into water vapour. Hence, water vapour gets continuously added to air. Evaporation takes place at all temperatures.

Condensation - It is the process by which water vapour is changed back into liquid water. Condensation is very important to our weather as it is responsible for cloud formation and bringing water back to the surface of the Earth. As water vapour rises into the atmosphere, it mixes up with very tiny particles of dust present in the atmosphere to form tiny droplets or ice crystals, if it is very cold. As more and more water particles and dust particles stick together, clouds are formed.

Precipitation - Precipitation occurs when the water drops become too heavy to float in the air, they fall on the Earth in the form of rain, hail or snow. Water stored in the clouds reaches Earth in the form of rain. It comes in the form of ice crystals or snow, if it is very cold.

 

FLOODS

Excessive rainfall leads to the situation of floods. Floods occur because of the overflow of water on adjoining land. During floods, the rivers, lakes and ponds are not able to hold the massive quantum of water caused by heavy downpour and it overflows from its normal path and spreads to a larger area. During flood, the roads and streets get submerged by water. It causes loss of life and property. It also causes damage to crops. Communication networks, water supply also get affected because of flood.

DROUGHTS

It does not rain for a long time in some parts of our country. Acute scarcity of water because of absence of rainfall for a long period of time leads to drought. During drought, rivers run dry, soil becomes dry and the level of groundwater also depletes. It affects the animals and vegetation of that region. Plants die because of lack of water and the animals which survive on plants also began to die.

CONSERVATION OF WATER

The main sources of water on Earth are rainwater, surface water and groundwater.

A very small fraction of water is readily available on Earth as fresh water. So it is very important to avoid wastage of water and use it economically and judiciously by following water saving practices. There are certain methods and techniques which can be used for conserving the water.

Rainwater Harvesting

Rainwater harvesting is the process of collecting and storing rainwater that collects on roofs instead of letting it go down the drain. It is one of the ways to conserve water. Rainwater harvesting plants are installed on roofs to harvest rainwater from roofs to be stored for later use. The harvested rainwater is stored in tanks and can be used later for domestic activities. The stored rainwater is treated before using, as it may contain impurities.

Another option for collecting rainwater is to allow water to go into the ground directly from the roadside drains that collect rainwater.

Fixing Leaky Taps

A lot of water is wasted through leaking taps. So the leaking taps must always be fixed to avoid wastage of water.

Building Dams

An artificial wall built across the river to collect water behind it in a reservoir is called dam. Dams are constructed to hold back water in order to prevent floods and to provide water for irrigation.

Water Pollution

Water pollution is also reason for the scarcity of water. Most of the rivers in our country and other sources of fresh water are polluted by industrial wastes or effluents. Industrial wastes discharged into the water bodies contain a lot of toxic substances that pollute the water and make it unfit for drinking. Reducing water pollution is also one of the ways to conserve the water.

Functions of Water

Water is very important for the proper functioning of the human body. It plays an important role in the process of respiration, digestion, metabolism and excretion.

• Water helps in regulating the temperature of the Earth by bringing rainfall and continuous circulation of water cycle.
• Water helps in regulating the body temperature.
• It helps in digestion of food.
• It helps in removing the waste produced in the body.

INTERESTING FACTS

• There is the same amount of water on Earth as there was when the Earth was formed.

• 75% of the human brain is water and 75% of a living tree is water.
• Frozen water (ice) is lighter than water, which is why ice floats in water.
• 10% of homes have leaking taps that waste 90 gallons or more water per day.
• Drinking too much water can be fatal and is known as water intoxication.
• If the entire world’s water were fit into a 4 litre jug, the fresh water available for us would equal only about one tablespoon.
• Pure water has no smell and no taste; it also has a pH level around 7.
• Today, at least 400 million people live in regions with severe water shortage.