Notes of chapter: Water: A Precious Resource are presented below. Indepth notes along with worksheets and NCERT Solutions for Class 7.
(1) We celebrate world water day on 22 March to realise the human being for importance of conserving water.
(2) A minimum of 50 litres per person per day for drinking, washing, cooking and maintaining proper hygiene is recommended by the United Nations.
(3) In some places, people have to stand in long queues for water especially during summer. Sometimes, they fight to fill a bucket of water. People protest and march for demanding water for their daily needs.
(4) Problems faced by people are listing below-
(i) People do not get clean water. Sometimes chemicals are also present in the drinking water.
(ii) People have to stand in queues for a bucket of water.
(iii) Water leakage in municipality’s pipes is main problem because clean water flows on the roads, streets.
(5) It is estimated that in a few years from now more than one third of the people in the world could face water scarcity.
(6) The water on the earth is found in the seas, and oceans, rivers, lakes, ice caps, as ground water and in the atmosphere. It shares 71% of the earth’s surface. But, most of the water is not good for human consumption.
|Steps||Figure||Remark||Remark after removing water from the source|
|Fill about 20 litres of water in the bucket.||Assume this water represents all the water present on the earth.|
|Transfer 100 spoons of water from a tea soon of 5 ml capacity in to a bath mug.||This represents total freshwater on the earth.||Saline water left in the bucket which is present in the seas, oceans and partly as groundwater. This water is not fit for human use.
|From the bath mug transfer 30 spoons of water to a glass tumbler.||This gives a measure of usable water present as groundwater.||The water left in the bath mug represents the water, which is present in the frozen form in glaciers, ice caps and permanent snow; not available readily.
|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.|
(i)We can not appreciate the actual amount of water available for human use because very less water is available for us in respect of its availability.
(ii) Steps to Save Water-
Findings of activity give serious impact on us. When there will be no water no living being can survive. Usable water is very less in quantity in respect of our need. So, we should take some steps to save water which are given below-
(a)Do not leave tap turn on.
(b)Do not let water leakage unattended.
(c)Use mug for shaving, brushing and for other activities.
(d)Take water for drinking purpose as much you needed.
(7) Water on the earth has been maintained for millions of years by various processes which make the water cycle. A cycle in which water continuously circulates between water sources (oceans, rivers, lakes etc.) and atmosphere because of continuous process of evaporation, precipitation and condensation is called water cycle.
(8) Water can be found in all three forms in the nature.
|S.N.||Form of water||Present in nature|
|1.||Solid||Snow and ice|
|2.||Liquid||Oceans, lakes, rivers and underground water|
The continuous cycling of water among its three forms keeps the total amount of water on the earth constant.
(9) Activity 2
Fig. given below shows the processes involved in the water cycle. They are labeled by numbers. Match these numbers with the processes given in the jumbled form.
(1) ground water
(10) Civic bodies supply water in the cities. They draw water from source and supply it through pipes. But, many villages do not have this facility. Women and children have to walk several kilometers to fetch water. Education of these children suffers a lot.
(11) Water Table-
Upper limit of ground water below which all the space between particles of soil and gaps between rocks are filled with water, is known as water table.
The process of seeping of water from rain, rivers, ponds etc. into the ground is called infiltration. So, the ground water gets recharged by this process.
Ground water between layers of hard rock below the water table is known as aquifer. Tube wells and handpumps can pumped out water from the aquifer.
(14)Level of water in water tables remains unaffected if water tables get back same quantity of water by seeping of rainwater. But, it may go down if the water is not sufficiently replenished.
(15) Reasons of depletion of water table-
(i) Increase in population-
Increase in population creates demand for more houses, shops, offices etc. Increase in construction decreases open areas like parks, playgrounds.it leads to decrease in seepage of rainwater.
In spite of this, huge amount of water is needed for construction which is often taken from groundwater. So, we are fetching more ground water and allowing less seep into the ground. Level of water in water tables are depleting continuously.
(ii) Increase in industries-
The number of industries is increasing continuously. Every industry needs water for production. Most of the industries use ground water. So, ground water level is decreasing rapidly.
(iii) Drawing of ground water-
Farmers depend on rainfall for irrigation. Due to erratic rainfall canals suffer lack of water. Irrigation system is not available in all over India. So, farmers have to draw ground water for irrigation. This results in depletion of water table.
(16) Activity 3
|SN||Name of the industries||Product||Use of the product|
|1.||Dairy||milk||Dahi, paneer etc.|
|3.||Sugar||sugar||Sweets, tea etc.
(17) Distribution of water-
The distribution of water is unequal over the globe because of uneven rainfall. Some places have heavy rainfall. They are water rich regions and may get floods due to excessive rainfall. Some areas get less or very less rainfall. These areas are not water rich areas and known as deserts.
(18) Activity 4
Answer some questions given below regarding rainfall of your region.
(i) Name the place where you are living?
(ii) Are you blessed with sufficient rainfall?
(iii) Is there sufficient water available in your area throughout the year?
(i) I live in Delhi.
(ii) Yes, we are blessed with sufficient rainfall.
(iii) Yes, almost throughout the year we get water except in summer.
(19) Mismanagement of water takes place at the level of civic authorities and individuals.
Mismanagement of water by civic authorities-
(i)Leakage of water supply pipes doesn’t attend by authorities immediately which cause loss of precious water.
(ii)Rain water just flows away.
Mismanagement of water by individuals-
(i)We waste water while brushing teeth, shaving , bathing and in many activities.
(ii) Leaking taps is another source of huge water wastage.
(20) Steps can be taken by authorities to save water-
(i) Leakages of pipe should be done immediately.
(ii) Rain water should be collected in natural reservoirs or in tanks for different use as drinking, bathing, irrigation etc. It can recharge the groundwater. This technology is known as rainwater harvesting.
Bawris should be revived .These are very old system of collecting water for daily purposes. With the passes of time, bawris turn into place to throw garbage.
(iv) Drip harvesting-
Drip harvesting should be promoted among farmers. It is a technique of watering plants by making use of narrow tubing which delivers water directly at the base of the plant.
(21)Role of individuals to save water-
(i)Do not leave tap turn on.
(ii)Do not let water leakage unattended.
(iii)Use mug for shaving, brushing and for other activities.
(iv)Take water for drinking purpose as much you needed.
(v)Mop the floor instead of washing.
(22)Plants will die if they do not get water. Without plants living organisms will have to face difficulty in finding food, oxygen, shelter etc. Thus, there will be no life without water.