Page 1 :
16, , Water: A Precious, Resource, , “Jal Hai, To Kal Hai”, “If you have water, you can think of the future”, You are perhaps aware that 22 March is, celebrated as the world water day! A, school celebrated ‘water day’ and invited, posters from the children of your age, group. Some of the posters presented, on that day are shown in Fig. 16.1., , Fig. 16.1 Collage of posters, , What is the message you get from, these posters? Write your observations, in your notebook and discuss them in, the class., Have you ever felt a shortage of water, at home or at school? Your parents or, , teachers must very often be advising you, not to waste water. No wonder we, celebrate water day every year to attract, the attention of everybody towards the, importance of conserving water., The amount of water recommended, by the United Nations for drinking,, washing, cooking and maintaining proper, hygiene is a minimum of 50 litres per, person per day. This amount is about, two and a half buckets of water per, person per day. Is your family getting at, least this much of water? If yes, you, should consider yourself fortunate, because millions of people in our, country do not get enough water. What, about your friends and their families?, Share your experience with them., In some places there is an acute, shortage of water. Taps running dry,, long queues for water (Fig. 16.2), fights,, marches and protests for demand of, water have become a common sight,, especially during summers. Some of the, newspaper clippings shown in Fig. 16.3, clearly indicate this message. Is it not, true that we face acute shortage of, water?, , 2020-21

Page 2 :
Fig. 16.2 Long queue for water, Fig. 16.3 Newspaper clippings, , Activity 16.1, Collect clippings from newspapers and, magazines on the news items, articles, and pictures related to water shortage., Paste them in your scrapbook and share, it with your friends. List some problems, faced by the people and discuss them, in the class., Water shortage has become a matter, of concern throughout the world. It is, estimated that in a few years from now, , Fig. 16.4 Earth appears blue from space, , Year 2003 was observed as, the International Year of, Freshwater to make people, aware of this dwindling natural resource., more than one third of the people in, the world could face water scarcity., Before we discuss why water is, getting scarce we must know how much, water is available for use on our planet., , 16.1 HOW MUCH WATER, AVAILABLE, , IS, , Look at the picture of the earth taken, from space. Why does it appear blue?, Surely, you can guess!, You are aware that about 71% of, the earth’s surface is covered with, water. 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 directly. The water, , 194, , SCIENCE, , 2020-21

Page 3 :
that is fit for use is freshwater. Perform, the following activity to estimate roughly, the relative amount of water available, in some of these sources., Steps, , Activity 16.2, Most of us assume water to be a limitless, resource. From this activity can you, , Figure, , Remark, , Take a medium-sized bucket, and fill it up with water. It, contains about twenty litres 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 groundwater., , Finally take out a quarter (1/4th), spoonfull of water from the mug., , It represents all the water, present in all the lakes and, rivers of the world., , n, , n, , 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., , Boojho wondered about the, alarmingly small quantity of, water available for our use., , Paheli quickly calculated and, found that this amount is, roughly 0.006% of all water, found on the earth., , WATER: A PRECIOUS RESOURCE, , 195, , 2020-21

Page 4 :
appreciate the actual amount of water, available for human use? Does the, finding worry you? Discuss this in your, class., , 16.2 FORMS, , OF, , WATER, , Are you afraid that continuous use will, some day exhaust all the water available, for use? You know that water on the, earth has been maintained for millions, of years by various processes which, make the water cycle. You have studied, the water cycle in Class VI. Write in your, own words what you know about the, water cycle., You know that when water circulates, through the water cycle it can be found, in all the three forms, i.e., solid, liquid, and gas — at any given time somewhere, on the earth. The solid form, snow and, ice, is present as ice caps at the poles of, , the earth, snow-covered mountains and, glaciers. Liquid water is present in, oceans, lakes, rivers, and even, underground. The gaseous form is the, water vapour present in the air around, us. The continuous cycling of water, among its three forms keeps the total, amount of water on the earth constant, even when the whole world is using it., Does it give you any relief?, Can you recall the processes involved, in water cycle? The following activity will, help you., , Activity 16.3, Fig. 16.5 shows the processes involved, in the water cycle. They are labelled by, numbers. Match these numbers with, the processes given in the jumbled form., Most towns and cities have water, supply system maintained by the civic, 1. rudgon rawet, , 4, 3, , 2. atooniaervp, , 7, 3. acestoonnnid, , 5, , 4. duclos, , 2, 6, , 5. tspratniaoinr, , 6. aitfinlronit, , 7. ntciepirtaipo, , 1, Fig. 16.5 Water cycle, 196, , SCIENCE, , 2020-21

Page 5 :
bodies. The water is drawn from, nearby lakes, rivers, ponds or, wells. The water is supplied, through a network of pipes., Many villages do not have such, a water supply system. There, people fetch water directly from, the sources. Often people and, even children have to walk, several kilometres to fetch water, (Fig. 16.6). The children suffer, a lot. They cannot attend, school regularly since they, spend hours in fetching water., Fig. 16.6 Women fetching water, , Women have to, perform a number of, household chores. If they have, also to spend time to fetch water, it adds to their burden., , A large number of people draw water, from wells, tube wells or hand pumps., From where do these sources get water?, , 16.3 GROUNDWATER AS AN, IMPORTANT SOURCE OF WATER, If we dig a hole in the ground near a, water body we may find that the soil is, moist. The moisture in the soil indicates, the presence of water underground. If, we dig deeper and deeper, we would, reach a level where all the space between, particles of soil and gaps between rocks, are filled with water (Fig. 16.7). The, upper level of this layer is called the, water table. The water table varies from, , place to place, and it may even change, at a given place. The water table may be, at a depth of less than a metre or may, be several metres below the ground. The, water found below the water table is, called groundwater. What is the source, of this groundwater?, The rainwater 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 groundwater thus gets recharged, by this process. At places the, groundwater 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 handpumps., Have you ever been to a site where, construction work is going on? From, , WATER: A PRECIOUS RESOURCE, , 197, , 2020-21

Page 6 :
Hand pump, , Stream or lake, Recharge, Water table, , Aquifer, Groundwater, Fig. 16.7 Groundwater and water table, , where do the workers get water for, construction? May be you have seen, boring being done at such sites to reach, the water table. Enquire from the people, working there how deep they have to dig., Can we keep on drawing water from, under the ground? How will it affect the, water table?, , agricultural activities are some common, factors affecting water table. Scanty, rainfall is another factor that may, deplete the water table. Yet another, factor affecting water table could be, deforestation and decrease in the, effective area for seepage of water., , 16.4 DEPLETION, , Increasing population creates demand, for construction of houses, shops,, offices, roads and pavements. This, decreases the open areas like parks, and, playgrounds. This, in turn, decreases the, seepage of rainwater into the ground., What could be the consequence? Recall, that a pukka floor does not allow water, to seep in easily, while in a grass lawn, water seeps through in no time., , OF, , WATER TABLE, , Water drawn from under the ground gets, restored by seepage of rainwater. The, water table does not get affected as long, as we draw as much water as is, replenished by natural processes., However, water table may go down if the, water is not sufficiently replenished., This may happen due to many reasons., Increase in population, industrial and, , Increasing population, , 198, , SCIENCE, , 2020-21

Page 7 :
Moreover a huge amount of water is, required for construction work. Often, groundwater is used for this purpose., So, on the one hand we are, consuming more groundwater, and on, the other we are allowing lesser water, to seep into the ground. This results in, depletion of water table. In fact, the, water table in some parts of many cities, has gone down to alarmingly low levels., , Increasing industries, Water is used by all the industries., Almost everything that 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., , Activity 16.4, , day by day. This results in depletion of, water table., , 16.5 DISTRIBUTION, , OF, , WATER, , The distribution of water over the globe, is quite uneven due to a number of, factors., Some places have good amount of, rain and are water-rich. On the other, hand, there are deserts which have, scanty rainfall., India is a vast country and the, rainfall is not the same everywhere., Some regions have excessive rains while, some others have very little rainfall., Excessive rains cause floods, whereas, the absence of rains results in droughts., Therefore, some regions in our country, may have floods while others may suffer, from droughts at the same time., , Activity 16.5, , Name some industries familiar to you., Make a list of the products obtained, from these and used in our daily life., Discuss with your teacher and parents, how the growing industrial activity is, responsible for the depletion of water, table., , Agricultural activities, A majority of farmers in India depend, upon rains for irrigating their crops., Irrigation systems such as canals are, there only in a few places. Even these, systems may suffer from lack of water, due to erratic rainfall. Therefore, farmers, have to use groundwater for irrigation., Population pressure on agriculture, forces increasing use of groundwater, , Given here is the rainfall map of India, (Fig. 16.8). It gives the average annual, rainfall in different regions of our country., n, Locate on the map the place you live, in., n, Are you blessed with sufficient, rainfall?, n, Is there sufficient water available in, your area throughout the year?, It may be possible that we are living, in an area where there is sufficient, rainfall yet there is shortage of water. Can, we attribute this to mismanagement of, water resources?, , 16.6 WATER MANAGEMENT, You have read in Class VI that in many, places a regular supply of water is, , WATER: A PRECIOUS RESOURCE, , 199, , 2020-21

Page 8 :
Fig. 16.8 Rain map of India, 1., 2., 3., 4., , Government of India, Copyright 2007., Based upon Survey of India map with the permission of the Surveyor General of India., The territorial waters of India extend into the sea to a distance of twelve nautical miles measured from the appropriate baseline., The external boundaries and coastlines of India agree with the Record/Master Copy certified by Survey of India., , 200, , SCIENCE, , 2020-21

Page 9 :
provided by a well-planned pipe system., When the civic authorities supply water, through pipes not all of it may reach, the destination. You might have seen, water supply pipes leaking and a lot of, water gushing out of the pipes. It is, the responsibility of the civic, authorities to prevent such wastage of, precious water., Mismanagement or wastage may, take place at the level of individuals also., All of us, knowingly or unknowingly,, waste water while brushing teeth,, shaving, bathing, washing and during, many other activities. Leaking taps is, another source of huge water wastage., We waste water as though we do not need, water the next time!, We have seen that most of the water, that we get as rainfall just flows away., This is a waste of precious natural, resource. The rainwater can be used to, recharge the groundwater. This is, referred to as water harvesting or, , rainwater harvesting, about which you, have learnt in Class VI., Find out if the buildings in your, neighbourhood have water harvesting, systems installed., We have at many places in India an, age old practice of water storage and, water recharge like the bawris. Bawri, was the traditional way of collecting, water. With time the bawris fell into, disuse and garbage started piling in these, reservoirs. However, because of the acute, water shortage, people in these areas, have had to rethink. The bawris are being, revived. Today the situation is that inspite, of scanty rains these places are, managing their water needs well., A farmer using water in the field can, also use water economically. Maybe, you have heard of drip irrigation, (Fig. 16.9). Drip irrigation is a technique, of watering plants by making use of, narrow tubings which deliver water, directly at the base of the plant., , A case study, Bhujpur in the Kutch area of Gujarat has a very erratic rainfall. The only source, of freshwater lies underground because rivers in this area do not have water, throughout the year. Over the years, demand for water has grown. The withdrawal, of groundwater has far exceeded recharge. As a result the water table has gone, down alarmingly., In 1989, the villagers along with a non-governmental organisation, decided to, harvest rainwater. Eighteen check-dams were built on the Rukmavati river and, its many tributaries. The water so collected increased percolation through the, soil and recharged the aquifers., According to farmers, the wells have water now and the water that flowed into, the sea and was wasted has become available for irrigation., WATER: A PRECIOUS RESOURCE, , 201, , 2020-21

Page 10 :
Water-wise habits, 1. Turn off taps while, brushing, 2. Mop the floor instead of, washing, , 16.8 EFFECT OF WATER SCARCITY, PLANTS, Fig. 16.9 Drip irrigation in a field, , 16.7 WHAT ROLE YOU, , CAN, , PLAY, , Have you ever shown concern if you saw, a tap leaking in your house, school or, any other place? Leaking taps waste a, lot of water. You must make efforts to, stop this leakage., There are a number of ways you can, adopt to minimise the wastage of water., Let us begin. We have given a few, examples. Add on!, , ON, , You must have seen potted plants, wilting and ultimately drying up if they, did not get water even for a few days., You have already learnt in Chapter 1, that plants need water to get nutrients, from the soil to prepare their food. Just, imagine the consequences if water is not, available to plants!, The green character of the planet, shall be lost. This may mean the end, of all life, for a world without plants, shall mean no food, no oxygen, not, enough rain, and innumerable other, problems., , A successful initiative, Rajasthan is a hot and dry place. The challenge of natural scarcity of water was, met by a successful experiment. A band of social workers has transformed a dry, area in the Alwar district into a green place. They have revived five dried-up, rivers — Arveri, Ruparel, Sarsa, Bhagani and Jahazwali by constructing waterharvesting structures., , “Hamara Jal – Hamara Jeevan”, Keywords, Aquifer, , Groundwater, , Water harvesting, , Depletion, , Infiltration, , Water table, , Drip irrigation, , Recharge, , 202, , SCIENCE, , 2020-21

Page 11 :
What you have learnt, n, , Water is essential for all living beings. There can be no life without it., , n, , Water exists in three forms: solid, liquid and vapour., , n, , Though water is maintained by the water cycle, yet there is an acute, scarcity of water in many parts of the globe., , n, , There is an uneven distribution of water. Much of it has resulted from, human activities., , n, , Rapid growth of industries, increasing population, growing irrigation, requirements and mismanagement are some of the causes for water, shortage., , n, , We need to be worried about the wastage during the supply of water, through pipes, the leaking taps in buildings and other places., Unnecessary use of water and overdrawing from groundwater should be, avoided. Recharge of water to the ground should be increased., , n, , The need of the hour is that every individual uses water economically., , n, , Plants wilt and ultimately dry-up if they are not watered for a few days., , Exercises, 1. Mark ‘T’ if the statement is true and ‘F’ if it is false:, (a), , The freshwater stored in the ground is much more than that, present in the rivers and lakes of the world. (T/F), , (b), , Water shortage is a problem faced only by people living in rural, areas. (T/F), , (c), , Water from rivers is the only source for irrigation in the fields. (T/F), , (d), , Rain is the ultimate source of water. (T/F), , 2. Explain how groundwater is recharged?, 3. There are ten tubewells in a lane of fifty houses. What could be the long, term impact on the water table?, 4. You have been asked to maintain a garden. How will you minimise the, use of water?, 5. Explain the factors responsible for the depletion of water table., 6. Fill in the blanks with the appropriate answers:, (a), , People obtain groundwater through________ and ________., , WATER: A PRECIOUS RESOURCE, , 203, , 2020-21

Page 12 :
(b), , Three forms of water are ________, ________ and ________., , (c), , The water bearing layer of the earth is ________., , (d), , The process of water seepage into the ground is called ________., , 7. Which one of the following is not responsbile for water shortage?, (i), , Rapid growth of industries, , (ii), , Increasing population, , (iii), , Heavy rainfall, , (iv), , Mismanagement of water resources, , 8. Choose the correct option. The total water, (i), , in the lakes and rivers of the world remains constant., , (ii), , under the ground remains constant., , (iii), , in the seas and oceans of the world remains constant., , (iv), , of the world remains constant., , 9. Make a sketch showing groundwater and water table. Label it., , Extended Learning — Activities and Projects, 1. Role play, You are a water detective in your school. You have a team of six, members. Survey the campus and make a note of the following:, (a), , Total number of taps, , (b), , Number of taps leaking, , (c), , Amount of water wasted due to leakage, , (d), , Reasons of leakage, , (e), , Corrective measures taken, , 2. Groundwater pumped out, Try to find out if there are any hand pumps in your neighbourhood. Go, to the owner or the users of a few of these and find out the depth at, which they struck water? If there are any differences, think of the, probable reason. Write a brief report and discuss it in your class. If, possible, visit a place where boring is going on to install a hand pump., Watch the process carefully and find out the depth of the water table at, that place., 3. Catching rainwater — Traditional methods, Form groups of 4 to 5 students in the class and prepare a report on the, various traditional ways of water harvesting. If possible, use the, following web link: www.rainwaterharvesting.org., 204, , SCIENCE, , 2020-21

Page 13 :
4. Conservation of water, Carrry out a campaign to conserve water at home and in the school., Design posters to remind others of the importance of water resources., 5. Create a logo, Hold a competition to create a logo or a symbol depicting water scarcity., , Did you know?, The importance of water management has been highlighted by a watershed, management project near the village of Kothapally. The project has yielded, dramatic results. Groundwater levels have risen, green cover has, increased, and productivity and incomes in this semi-arid region have, dramatically improved., , WATER: A PRECIOUS RESOURCE, , 205, , 2020-21