Class 7 Science Chapter 16 Important Questions

Explain how the water is wasted at individual level.
There are various reasons of wastage of water at individual level. All of us waste water while brushing teeth, shaving, bathing, washing and during various other activities. Leaking taps are also big source of huge water wastage. We generally leave the taps running at public places. This habit makes use lots of potable water.

All of us need water every day for drinking, cooking food, washing, brushing teeth, bathing and flushing toilets and for etc. work. UN recommended the amount of water for per person is 50 liters per day. Millions of people in our country do not get sufficient water in some place. There is an acute shortage of water especially during summers. In this case women and children usually walk several kilometers daily with pitchers on their heads to fetch water for their households. This harms the woman as well as children life. The village children suffer because they spend hours in fetching water due to which they cannot attend their school regularly. In fact, water shortage has become a matter of concern throughout the world. It is estimated that in a few years from now more than one third of the people in the world could face water shortage.

How does people of Rajasthan overcome the challenge of erratic rain fall?
Rajasthan is a hot and dry place which gets erratic rainfall. The challenge of natural scarcity of water has been successfully overcome by the collective actions of the people. A number of social workers have revived five dried up rivers Arveri, Sarsa, Bhagani, Ruparel, Jahaz-wali, by constructing rainwater harvesting structures. The increased water available has transformed a dry area in the “Alwar district of Rajasthan” into a lush green area.

About 71% of the Earth’s surface is covered with water. The total water present on the earth about 97.4 percent is in the seas and oceans. The water which is fit for use by human beings is called freshwater. Only 2.6 % of the total water on the earth is the freshwater. Almost all the water on the earth is contained in the seas and oceans, rivers, lakes, ice caps, as groundwater and in the atmosphere. However, most of this water is not fit for human consumption. Perform the following activity to estimate roughly the relative amount of water available in some of these sources.
Take a medium-sized bucket and fill it up with water. It contains about twenty liters of water. Assume that this water represents all the water present on the earth. Take a tea spoon of about 5 mL capacity and transfer 100 spoons of water from the bucket to a small container, like a bath mug. This represents total freshwater on the earth. From the bath mug transfer thirty spoons of water to a glass tumbler. This gives a measure of usable water present as ground- water. Finally take out a quarter (1/4th) spoonful of water from the mug. It represents all the water present in all the lakes and rivers of the world. The water left in the bucket represents the saline water present in the seas, oceans and partly as groundwater. This water is not fit for human use. The water left in the bath mug represents the water, which is present in the frozen form in glaciers, ice caps and permanent snow; again, not available readily.

Write down the exact reason for the shortage of water.
The main reason for the shortage of water or scarcity of water are increasing population, growing irrigation requirements of agriculture, rapid growth of industries and mismanagement of water.

The rain water and water from other sources such as rivers, lakes and ponds etc., seeps through the ground and fills the empty spaces between the soil and the rocks below the earth. The water keeps on seeping deeper and deeper into the ground through the soil and permeable rocks until it reaches an impermeable rock or hard rock.
So, water starts collecting above the impermeable rock and fills the soil and permeable rocks completely with water up to the level known as water table. The underground layer of soil and permeable rocks in which water collects under the ground is called an “aquifer”. The top of aquifer is referred to as “water table”. Aquifer stores and provides ground water. The rainwater which seeps into the ground ultimately reaches the aquifer and gets stored there.
We take out groundwater for our use with the help of wells, tube wells and handpumps. This decreases the amount of groundwater. But when it rains, the rain water seeps into the ground and the groundwater is recharged.

Explain the reason behind the depletion of water table.
There are some of the factors which affect water table, at a place and make it go down as increasing populations, industrial and agricultural activities, scanty rainfall, deforestation and decrease in the effective area for seepage of rainwater.

• i) Increasing population needs more and more water for its day-to-day activities. So, due to increasing population, on the other hand we are consuming more groundwater and we are allowing less rain water to seep into the ground. This leads to the depletion of water table.
• ii) Industries produce a large number of various types of things which we use in our everyday life. As the population is increasing the demand for various industrial goods is increasing, and hence the number of industries is also increasing continuously. As a number of industries is increasing, the water drawn from the ground for their use is also increasing.
• iii) The growing of various crops in agriculture requires a lot of water for irrigation. In India, a majority of farmers depend on rains for irrigating their crops. As more and more food has to be grown for increasing population, the use of groundwater for agriculture is increasing day by day.
• iv) Sometimes there is scanty rainfall during the rainy seasons. In such a situation, much more ground water is drawn out by the people for various purposes. This leads to the depletion of water table.
• v) Deforestation is the cutting down of trees and plants from the forest for various purposes. We know that forests help in bringing rain. So lesser number of trees and plants in the forest will bring less rainfall. If there are lesser number of trees and plants in the forest, less rain water will seep into the ground. This depletes the water table.
• vi) Due to increasing urbanization and industrialization more and more space is being covered by houses, buildings, roads etc., and the open spaces having unpaved ground are getting reduced day by day. This leads to the depletion of water table.

We are living in an area where there is sufficient rainfall but it may be possible, yet there is shortage of water. This can happen, if there is mismanagement of water resources.

1. At many places water is supplied through a well-planned network of big and small pipes. Many times, we have seen the big water supply pipes leaking and a lot of water gushing out of these pipes. The leaking pipes lead to the wastage of precious water.
2. All of us knowingly or unknowingly waste a lot of water while brushing teeth, shaving, bathing, washing clothes, washing utensils, watering the plants and during many other activities. Leaking taps in our houses are another source of huge water wastage.
3. Most of the rain water which falls around us during rainy season just flows away into dirty water drains and becomes useless. This is the wastage of precious natural resource of water. The concerned Government Department as well as the public are responsible for the mismanagement and wastage of this rainwater. This is because rain water can be used to recharge groundwater for future use.

Water is very precious for all the living being. What will happen in future, if we do not save water now?
Water is needed for various life activities. If we continue the misuse of water and do not conserve it, the groundwater level will be depleted. This may result into various consequences like:

• i) Lowering of the water table, excessive pumping can lower the groundwater table.
• ii) Reduce surface water supply, groundwater and surface water are connected. When groundwater is over used, the lakes, streams and rivers connected to ground water, can also have little supply.
• iii) Loss of plants from land, we fully dependent on the plants for food directly or indirectly. Plants, need water to prepare their food. If there will be scarcity of water on earth, the plant will be unable to prepare their food. This in-turn will lead to the end of the life because world without plants means no food, no oxygen, not enough rain and other innumerable problems. Therefore, it is true that water is a precious resource.

We can save water at home by minimizing its wastage in the following manner:

1. Mop the floor instead of washing it daily.
2. Do not use a full flush from the cistern in the toilet when a half flush is sufficient.
3. Use the water from washing rice, vegetables or fruits for watering the plants at home.
4. Take bath by filling water in a bucket and not directly under the following tap. Wash the utensil by filling water in a basin and not under the running tap.
5. Do not keep the tap running all the time while brushing the teeth.
6. And one of the most imported, get the leaking taps repaired immediately because leaking taps waste a lot of water.