16Resource Water: A Precious - NCERT

1 water : A PreciousResource16 You are perhaps aware that 22 March iscelebrated as the world water day! Aschool celebrated water day and invitedposters from the children of your agegroup. Some of the posters presentedon that day are shown in Fig. Jal Hai, To Kal Hai If you have water , you can think of the future teachers must very often be advising younot to waste water . No wonder wecelebrate water day every year to attractthe attention of everybody towards theimportance of conserving amount of water recommendedby the United Nations for drinking,washing, cooking and maintaining properhygiene is a minimum of 50 litres perperson per day. This amount is abouttwo and a half buckets of water perperson per day. Is your family getting atleast this much of water ?

2 If yes, youshould consider yourself fortunatebecause millions of people in ourcountry do not get enough water . Whatabout your friends and their families?Share your experience with some places there is an acuteshortage of water . Taps running dry,long queues for water (Fig. ), fights,marches and protests for demand ofwater have become a common sight,especially during summers. Some of thenewspaper clippings shown in Fig. indicate this message. Is it nottrue that we face acute shortage ofwater?Fig. Collage of postersWhat is the message you get fromthese posters? Write your observationsin your notebook and discuss them inthe you ever felt a shortage of waterat home or at school? Your parents or2022-23 SCIENCE194 Activity clippings from newspapers andmagazines on the news items, articlesand pictures related to water them in your scrapbook and shareit with your friends.

3 List some problemsfaced by the people and discuss themin the shortage has become a matterof concern throughout the world. It isestimated that in a few years from nowFig. Earth appears blue from spaceFig. Long queue for waterFig. Newspaper clippingsYear 2003 was observed asthe International Year ofFreshwater to make peopleaware of this dwindling natural than one third of the people inthe world could face water we discuss why water isgetting scarce we must know how muchwater is available for use on our HOW MUCH water ISAVAILABLELook at the picture of the earth takenfrom space. Why does it appear blue?Surely, you can guess!You are aware that about 71% ofthe earth s surface is covered withwater. Almost all the water on theearth is contained in the seas andoceans, rivers, lakes, ice caps, asgroundwater and in the , most of this water is not fit forhuman consumption directly.

4 The water2022-23 water : A Precious RESOURCE195 Paheli quickly calculated andfound that this amount isroughly of all waterfound on the is fit for use is freshwater. Performthe following activity to estimate roughlythe relative amount of water availablein some of these of us assume water to be a limitlessresource. From this activity can youRemarkAssume that this waterrepresents all the water presenton the represents totalfreshwater on the gives a measure of usablewater present as represents all the waterpresent in all the lakes andrivers of the a medium-sized bucketand fill it up with water . Itcontains about twenty litres ofwater. Take a tea spoon of about 5 mLcapacity and transfer 100spoons of water from the bucketto a small container, like a the bath mug transferthirty spoons of water to a take out a quarter (1/4th)spoonfull of water from the water left in the bucket represents the saline water present in the seas,oceans and partly as groundwater .

5 This water is not fit for human water left in the bath mug represents the water , which is present in thefrozen form in glaciers, ice caps and permanent snow; again not available wondered about thealarmingly small quantity ofwater available for our the actual amount of wateravailable for human use? Does thefinding worry you? Discuss this in FORMS OF WATERAre you afraid that continuous use willsome day exhaust all the water availablefor use? You know that water on theearth has been maintained for millionsof years by various processes whichmake the water cycle. You have studiedthe water cycle in Class VI. Write in yourown words what you know about thewater know that when water circulatesthrough the water cycle it can be foundin all the three forms, , solid, liquidand gas at any given time somewhereon the earth.

6 The solid form, snow andice, is present as ice caps at the poles ofthe earth, snow-covered mountains andglaciers. Liquid water is present inoceans, lakes, rivers, and evenunderground. The gaseous form is thewater vapour present in the air aroundus. The continuous cycling of wateramong its three forms keeps the totalamount of water on the earth constanteven when the whole world is using it give you any relief?Can you recall the processes involvedin water cycle? The following activity willhelp shows the processes involvedin the water cycle. They are labelled bynumbers. Match these numbers withthe processes given in the jumbled towns and cities have watersupply system maintained by the civic1. rudgon rawet2. atooniaervp3. acestoonnnid4.

7 Duclos5. tspratniaoinr6. aitfinlronit7. ntciepirtaipoFig. water cycle32561742022-23 water : A Precious RESOURCE197bodies. The water is drawn fromnearby lakes, rivers, ponds orwells. The water is suppliedthrough a network of villages do not have sucha water supply system. Therepeople fetch water directly fromthe sources. Often people andeven children have to walkseveral kilometres to fetch water (Fig. ). The children suffera lot. They cannot attendschool regularly since theyspend hours in fetching to place, and it may even changeat a given place. The water table may beat a depth of less than a metre or maybe several metres below the ground. Thewater found below the water table iscalled groundwater . What is the sourceof this groundwater ?

8 The rainwater and water from othersources such as rivers and ponds seepsthrough the soil and fills the emptyspaces and cracks deep below theground. The process of seeping of waterinto the ground is called groundwater thus gets rechargedby this process. At places thegroundwater is stored between layers ofhard rock below the water table. This isknown as an aquifer. water in theaquifers can be usually pumped out withthe help of tube wells or you ever been to a site whereconstruction work is going on? FromWomen have toperform a number ofhousehold chores. If they havealso to spend time to fetch waterit adds to their large number of people draw waterfrom wells, tube wells or hand where do these sources get water ? groundwater AS ANIMPORTANT SOURCE OF WATERIf we dig a hole in the ground near awater body we may find that the soil ismoist.

9 The moisture in the soil indicatesthe presence of water underground. Ifwe dig deeper and deeper, we wouldreach a level where all the space betweenparticles of soil and gaps between rocksare filled with water (Fig. ). Theupper level of this layer is called thewater table. The water table varies fromFig. Women fetching water2022-23 SCIENCE198where do the workers get water forconstruction? May be you have seenboring being done at such sites to reachthe water table. Enquire from the peopleworking there how deep they have to we keep on drawing water fromunder the ground? How will it affect thewater table? DEPLETION OF water TABLEW ater drawn from under the ground getsrestored by seepage of rainwater. Thewater table does not get affected as longas we draw as much water as isreplenished by natural , water table may go down if thewater is not sufficiently may happen due to many in population, industrial andagricultural activities are some commonfactors affecting water table.

10 Scantyrainfall is another factor that maydeplete the water table. Yet anotherfactor affecting water table could bedeforestation and decrease in theeffective area for seepage of populationIncreasing population creates demandfor construction of houses, shops,offices, roads and pavements. Thisdecreases the open areas like parks, andplaygrounds. This, in turn, decreases theseepage of rainwater into the could be the consequence? Recallthat a pukka floor does not allow waterto seep in easily, while in a grass lawnwater seeps through in no groundwater and water tableStream or lakeGroundwaterAquiferWater tableRechargeHand pump2022-23 water : A Precious RESOURCE199 Moreover a huge amount of water isrequired for construction work. Oftengroundwater is used for this , on the one hand we areconsuming more groundwater , and onthe other we are allowing lesser waterto seep into the ground.