- 1 Water: It is one of the most important substances needed by living beings for life. We can live without food but not without water and air. Water is an essential natural resource. It is known as the first type or primary resource.
- 2 Uses of Water
Water: It is one of the most important substances needed by living beings for life. We can live without food but not without water and air. Water is an essential natural resource. It is known as the first type or primary resource.
Uses of Water
Some of the uses are:
(a) Water is used for drinking, bathing and washing our clothes.
(b) Water is also used for cooking, cleaning of utensils and for other activities.
(c) Water is also needed for the germination of seeds and watering of plants.
(d) It is required by green plants for photosynthesis, i.e., making food.
(e) Water is required for the irrigation of crops, which results in the growth of crop plants and the production of food grains.
(f) Water is required for tanning of leather, the printing of clothes and manufacturing paper.
(g) Water is also needed for digestion of food, absorption of digested food and excretion of water products.
(h) Water is required for maintaining the body temperature of an organism.
(i) Water dams use water for generating electricity.
(j) It helps in regulating the climate of a place.
(k) Water is also used for recreation, e.g., swimming, water surfing, boat race, water polo, etc.
SOURCES OF WATER
Various natural sources of water are as follow:-
1. Oceans and Seas. They are the main sources of water found on the earth’s surface. They are considered to be the largest body of water on the surface of the earth. The water present in oceans and seas covers nearly 3/4th of the earth’s surface. But this water contains a large number of salts dissolved in it. Hence, this water is neither fit for drinking nor for agriculture. Ocean water can be purified and can be used for various activities. Seas and oceans are habitats for the huge marine life.
2. Snow. Another important source of water is in its solid form known as snow. Snow is the solid form of precipitation which occurs if the temperature is below 0°C in that region. Water obtained by melting of snow forms rivers and river water is available on the plain. Snow is found on high mountains and in polar regions.
3. Rivers and Springs. Sources of freshwater are rivers and springs. Rivers are an important resource of water and are used for various activities. Most of the water used by us for cooking, drinking, washing, farming comes from rivers.
Those regions of the world which are located near rivers are more prosperous. Presence of water also helps in the development of civilisation because more and more people settle around river valleys as water is required for living, agriculture, growth of industries and transportation.
As rivers flow down the mountains, the water gets trapped inside cracks and comes out at open places in the form of springs.
4. Underground water. The water that is collected below the ground surface is called underground water. Underground water can be used in the form of well. At many places, the earth surface is dug up to obtain water. The well water is used by us for many activities. Groundwater is also used by plants. Roots of the plants absorb groundwater and use it for photosynthesis. Groundwater also has minerals dissolved in it which are required by plants for their growth.
At a certain level below the earth, all the space is covered with water. This level is called Water Table.
In a region where there is more rainfall, the water table is always high. More the water table, better is the growth of plants at that place which results in the formation of forest cover.
5. Lakes and Ponds. Lakes and ponds are other sources of freshwater as these are filled by rivers and rain. Lakes and ponds are formed by the collection of rainwater in low-lying areas of the earth. You might have seen or heard about the Lake Naini and Dal Lake of Kashmir. They are a source of water in those small areas. If the lakes have no opening, they form ponds but if they have an opening, then they are called lakes. Lakes get a continuous supply of fresh water from the rivers.
6. Rain. Rain is an important source of water. Rainwater fills the oceans, ponds, lakes, rivers, and seas. It also adds up to the groundwater and thus helps to maintain the water table of an area. Rain is very important as it helps to remove heat and cools the climate of a place.
Water is a nature’s precious gift to man. It is necessary to conserve and preserve this water so that it may be available for forthcoming generations in the future.
Due to the change in lifestyle and urbanization, the amount of water consumed by man is continuously increasing. These activities have resulted in pollution of water as well as wastage. One should use water judiciously so that this precious gift can be conserved.
Following steps should be taken to conserve water:-
1. Close the tap when no use of water.
2-Do not bath with shower.
3. Instead of using flush, use water from mug to clean the toilets.
4. The waste from industries must be first treated before disposing of it into water bodies.
5. The sewage water should be treated and used in the irrigation of crops.
6. Plant trees and other vegetation as they are good sources of absorbing water.
7. Build dams to store water.
8 Rainwater harvesting.
The circulation of water in the earth’s atmosphere is called the water cycle. Following are the steps of the water cycle:
1. Evaporation. Evaporation is a natural phenomenon that helps in converting water into water vapor using the sun’s energy. As a result of this process, water evaporates from seas, oceans, ponds, lakes, rivers, and other water bodies. Evaporation of water adds water vapor into the surrounding air.
Other Sources of Water Vapour
Plants also play a vital role in adding water vapour to the surroundings. Plants absorb water from the soil with the help of roots. A part of this water absorbed is used by plants for the growth and part of this water absorbed is used by plants for the growth and preparation of food (photosynthesis). A large part of the water is released into the surroundings as water vapour. This water is released through a small opening on leaves called stomata. This process of releasing water into the surrounding air in the form of water vapour is called transpiration. Transpiration produces a large amount of water vapour into the atmosphere.
2. Condensation. The next stage after evaporation is condensation. The water vapour cools down and gets condensed on the dust particles present in the air.
In winter, however, the temperature near the surface of the earth is cold. Hence, water vapour condenses to form fog which reduces the visibility as it is formed near the surface of the earth. The size of the fog particles is very small.
3. Formation of Clouds. The water vapour is being continuously added into the air by evaporation and transpiration. The water vapour rises up along with the air. In the upper layer of the atmosphere, the temperature is less so the air gets cooler and cooler, as we move up. At a particular height, the air becomes so cool that the water vapour present in the air condenses to form tiny droplets. These are so small that such droplets if join together, will form a drop of water. These droplets combine together to form large size, which is visible to us in the form of clouds.Thus, clouds contain a large number of water droplets joined together.
4. Precipitation. As we know that clouds carry a large number of water droplets with them. If the number of droplets is so large that they cannot be retained in the atmosphere, then these droplets fall on earth as rain, snow or hail. This is called precipitation.
Therefore, every time when you see clouds, it is not necessary that it will rain but rain or precipitation occurs only when the droplets become so large and heavy that they cannot be retained by clouds. Note:
STATES OF WATER
We all know that matter has three states – solid, liquid and gas. As water is also a form of matter thus it can exist in all the three states in nature on the earth:
• Solid, as ice in the polar regions and mountains.
• Liquid, as water in water bodies.
• Gas, as water vapour in the atmosphere.
Thus, the most common state of water is the liquid state. On heating water, it forms vapour. Water on cooling forms the solid state of matter called ice. All three forms are interchangeable.
In India, most of the rainfall takes place in monsoon season. Sometimes, it rains heavily and causes floods. Most of these rainwater flows in the seas. Government of India has constructed big dams wherever possible to harvest excess water in rivers and then use it for irrigation and drinking purposes.
In big cities such as Delhi, Mumbai and Chennai, vast spaces are covered by roads and buildings. The rainwater thus must be collected so that it is available throughout the year. This method of collecting and storing rainwater for later use is called rainwater harvesting.
It is done by:
1. Rooftop Rainwater Harvesting. In this system, rainwater from the rooftop is brought down by pipe which empties itself in the filter tank containing sand and pebbles. The water from the filter tank is then made to seep in another tank for storage.
2. Drain Water Harvesting. In this process, the rainwater flowing on the roads is collected through big pipes and is directly allowed to flow.
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