⛪Home⇐ Class VI Rain - Where does it come from


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Class VI - Science: Rain Where does it come from
One Word Answer Questions:
Q) Water in which state is present in oceans, lakes, rivers and underground?
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Q) The process of seeping of water into the ground is called?
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Q) The groundwater which is stored between layers of hard rock below the water table is known as?
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Q) Give one reason for depletion of water table?
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Q) Name the technique in which plants are watered through narrow tublings to deliver water directly to the base of the plant?
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Short Answer Questions:
Q) What is rainwater harvesting?
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Q) Give atleast two examples of wise habits to save water from wastage?
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Q) How is the mismanagement of water done by the individuals?
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Q) What is water table?
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Q) Explain the factors responsible for the depletion of water table?
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Q) What is water cycle? Explain the various forms of water?
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Long Answer Questions:
Q) What is the effect of water scarcity on plants?
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Q) Explain how groundwater is recharged?
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Activity:1
  • Take some water in a glass. Add some pieces of ice to it.
  • Observe for few minutes.
  • What changes do you observe on the outer surface of the glass? You would observe formation of small drops of water on the outer surface of the glass.
  • Why are these drops formed? Do they get formed if there is no ice in the glass?
  • Air around the glass contains water vapour which is warmer than the surface of the glass.
  • Due to the cold glass, air close to its surface will also become cooler.
  • This changes the water vapour in the air around the surface of the glass into water and forms small drops on the outer surface of glass.
  • Have you ever observed in your daily life where water vapour changes into water? List them out.
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Activity:2
  • Clouds in kitchen Take a vessel filled with water.
  • Keep it on a stove and heat it slowly. Observe for some time.
  • Now cover the vessel with a plate.
  • Remove the plate after a couple of minutes Do you see any changes on the inner surface of the plate?
  • Pour some cool water on the plate and observe what happens?
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  • What similarities do you find between evaporation of water from surface of water bodies and evaporation of water from a bowl heated in the kitchen?
  • From both cases discussed above, we know that water vapour helps to form clouds.
  • The clouds formed on the surface of the different water bodies do not stay there.
  • They start to move from one place to another in the direction of winds.
  • As more clouds come together they become laden with water vapour.
  • Winds bring the clouds from the sea to the land.
  • The colder air in the upper layers of the atmosphere cools the clouds.
  • Have you observed the colour of a cloud before rain?
  • How are clouds converted into rain? We all know that without clouds, it will not be possible to get rains and that all clouds do not cause rains.
  • Some changes take place in the clouds before they cause rain.
  • What changes do you notice in the sky and in the atmosphere before it rains?
  • What changes take place in clouds before raining?
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  • The clouds moving in air are generally at higher levels.
  • Sometimes the cool breeze coming along with air makes the clouds cooler.
  • This leads to water droplets present in the clouds to condense and form large water drops.
  • Further cooling of clouds increases the size of their water drops and clouds become heavy and descend towards the earth.
  • The colour of such clouds changes from white to gray giving us the feeling of dark clouds gathering.
  • When the size of the water drops increases further it becomes difficult for the cloud to hold them and water drops begin to fall. This is called "rain".
  • In our daily life, we observe that before raining, clouds descend towards the earth's surface and we experience a cool breeze before rainfall.
  • In very cold conditions, the drops of water turn into crystals of ice and fall as snow.
  • Sometimes big drops of water solidify into ice and fall as pieces of ice known as hailstones.
Water A Precious Resource

Water is very important for life. We need water to drink, to wash our hands, to cook, to water plants and many other things. Without water, the plants would die and people and animals would go thirsty.

Availability Of Water On Earth

About 71% of the earth's surface is filled with water. But out of this, a very small amount is available for the human use.

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  • If a bucketful of water shows the total water on the earth, then a mug of water shows the total freshwater available on the earth.
  • Out of this, a glass of water shows the water which is available as groundwater. About one-fourth spoonful of water shows all the water available in lakes and rivers of the world

Forms of Water

All of us know that water is available in nature in three forms.

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Solid Form
We call soild form of water ice.
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Liquid Form

If we heat ice, it will change into water. Water in liquid form is present in oceans, seas, lakes, rivers and even underground.

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Gaseous Form
  • The gaseous form of water is water vapour which is present in the air around us.
  • We know that when ice is heated it converts into water and if water is heated it turns into water vapour.
  • Similarly when water vapour is cooled.
  • If water is cooled further we will get ice. So, we understand that these three forms of water are interchangeable.
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Method             Method
                ICE     ↔     WATER     ↔     WATER VAPOUR
Cooled               Cooled

Water Cycle
  • Water is available in all the three states of matter. Ice is the solid state, water is the liquid state and vapour is the gaseous state; in which water is available.
  • The water on the earth keeps on changing in all the three states in a cycle. This is known as water cycle. The water cycle helps in keeping the amount of water on the earth as constant.
Following are the main steps of water cycle in nature
Evaporation

Water from the surface of the earth keeps on evaporating and turns into vapour. The water vapour also comes from green plants through transpiration.

Condensation

The water vapour condenses to from clouds.

Precipitation

Water from the clouds falls on the land; in the form of precipitation. At higher altitudes, the condensed water from the clouds also falls in the form of ice.

Collection
  • The rainwater falls on the ground and runs off to the nearest water bodies
  • Some of this water seeps down the ground to recharge the groundwater. Rest of the water goes to the ocean via rivers
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Groundwater
  • It is the most important source of water for us
  • The water is stored under the ground between layers of rocks
  • The upper limit of groundwater at a place is called the water table at that place.
  • The water found below the water table is called ground water
  • The rain water and water from other sources such as rivers and ponds seeps through the soil and fills the empty spaces and cracks deep below the ground
  • The process of seeping of water into the ground is called infiltration
  • The ground water thus gets recharged by this process. At places, the ground water is stored between layers of hard rock below the water table This is known as an aquifer
  • Water in the aquifers can be usually pumped out with the help of tube wells or hand pumps
  • Water table is usually higher in the plains but is very low in the plateaus. This is the reason it is easier to install a hand-pump in the northern plains.
  • On the other hand, it takes a heavy drilling machine to install a tube-well in the plateaus.
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    Groundwater And Water Table
    Depletion Of Water Table
    • Due to growing human population, there is an increased demand for potable water
    • There is more need for drinking water and also for water for other purposes like irrigation, economic activities and recreation
    • The supply of water either remains the same or has decreased, but demand has been continuously increasing
    • The mismatch in supply and demand is resulting in depletion of water table and most of the places are facing acute shortage of water
    Increasing population
    • Growing population means, there is more demand for food grains and hence farming is being done on a larger scale. More farming means more consumption of water for irrigation.
    • Growing population also means more construction of houses and pukka roads. This has created an impervious layer of concrete above the ground at most of the places.
    • This has adversely affected the natural recharge of underground aquifers.
    • Forests have been cut to clear land for meeting the demand of a growing population.
    • Trees make the rocks previous to water and thus facilitate recharge of underground aquifers.
    • Reduced forest cover has also hampered the natural recharge of underground aquifers.
    Increasing Industries
    • Water is used by all the industries. Almost everything we use needs water somewhere in its production process.
    • The number of industries is increasing continuously. Water used by most of the industries is drawn from the ground.
    Distribution Of Water
    Uneven Rainfall

    India is a large country. Some parts of the country get excess rainfall, while some other parts get deficient rainfall.
    As a result, while some parts of the country are flooded during the rainy season, many other parts suffer from draught like conditions.
    Uneven rainfall also adds to the problem of water shortage.

    Tackling of Water Shortage
    Rain Water Harvesting
    • Collection of rainwater for future use is called rainwater harvesting.
    • India has a long history of different rainwater harvesting structures; especially in rain deficient areas.
    • Example: Tanka's and Bawris had been in use in the northwestern part of India; especially in Rajasthan.

    • Tanka is an underground tank to collect rainwater.
    • Bawri is an open tank in which water used to be collected. Steps were made around the bawri so that one can easily access the water.
    • Rainwater harvesting can also be done in modern homes.
    • The runoff rainwater from the rooftop should be collected in an underground reservoir. Such reservoirs are usually filled with sand and gravel to filter out impurities from water.
    • The water can either be used directly or can be channelized to recharge the underground water.
    Drip Irrigation

    Drip irrigation is a method through which maximum number of plants can be irrigated with minimum use of water.For this, pipelines are laid throughout the rows of plants.
    Pipes are pierced at strategic points to release water in droplets. This helps in saving the water which is an important but scarce resource.

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    Drip Irrigation in A Field
    Steps One Can Take To Conserve Water
    • Immediately repair any leaking tap in the household.
    • Don't let the tap remain open while brushing your teeth.
    • Water left after washing or bathing can be used for mopping and for watering the plants.
    • Avoid using a shower and use a bucketful of water instead
    Effect Of Water Scarcity On Plants
    • As water is very essential for us, similarly plants also need water for their survival.
    • Water helps to transport the nutrients to other parts of the plant.
    • In the absence of water, the green character of the planet shall be lost. This means, the end of all life.
    • For a world without plants shall mean no food, no oxygen, not enough rain and innumerable other problems.
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