Water

Question 1 Name the three forms of water in which it circulates in nature during the water cycle?

Question 2 What are the causes for the shortage of water?

Question 3 Define the term precipitation and infiltration?  

Question 4 Explain the water cycle occurring in nature?

Reason : Why Water is essential to us ?

Water is essential for the existence of life. All the living things (human beings, other animals and plants) need water to live. Without water, there would be no living things on the earth.

Almost all the water on the earth is contained in the seas and oceans, rivers, lakes, ponds, snow-covered mountains, glaciers, polar ice caps, as groundwater and in the atmosphere.

 

The earth appears blue from space because a major part of the surface of earth is covered with water in seas and oceans. About 71 per cent of the earth’s surface is covered with water. Of the total water present on the earth, about 97.4 per cent is in the seas and oceans.

The sea water (or ocean water) is highly salty or saline. The saline water of seas and oceans is not fit for human consumption. The water which is fit for use by human beings is called freshwater. Only 2.6 per cent of the total water on the earth is the freshwater. Most of the freshwater is in frozen state (snow or ice) on snow covered mountains, glaciers and as polar ice caps (on the poles of the earth). This frozen fresh water is not readily available for human use. Only a small fraction of freshwater is readily available for use by human beings.

The water available for human use is mostly present in rivers, lakes, ponds, and partly as groundwater. The readily available freshwater available for use by us is only about 0.006 per cent of the total water present on the earth.

It is the water cycle taking place in nature continuously which converts some of the sea water (or ocean water) into freshwater in the form of rain and snowfall. It is due to the occurrence of water cycle in nature that even after continuous use by us, water does not get exhausted from land.

Water Cycle

(1) Oceans, rivers, lakes and ponds contain water in liquid form. Evaporation of water from oceans, rivers, lakes and ponds forms water vapour which goes into air.

(2) Water vapour is the gaseous form of water. The trees and plants suck groundwater through their roots. The trees and plants put some of this water into air as water vapour by the process of transpiration.

(3) The water vapour present in air rises high up in the sky, gets cooled and condenses of water vapour forms clouds. The clouds get cooled further and form rain clouds.

(4) The rain clouds make the droplets of water (formed by the condensation of water vapour) fall down on earth in the form of rain.

(5) Rain is the ultimate source of freshwater. In very cold regions, water drops in the sky freeze to form snow leading to snowfall. Snow is the solid form of water. The water which falls from clouds as rain or snow is called precipitation.

(6) Some of the rainwater (and water formed by the melting of snow) seeps into the ground. The process of seeping of water into the ground is called infiltration. Some of the rainwater fills the lakes and ponds. And the rest of rainwater flows in the rivers and finally goes into the oceans.

 

Forms of Water 

Water exists in three forms : solid, liquid and gas.

(1) Water is present in solid form (as snow and ice) on snow-covered mountains, glaciers and as ice caps on the poles of the earth.

(2) Water is present in liquid form in oceans, rivers, lakes, ponds and under the ground.

(3) Water is present in gas form (or gaseous form) as water vapour in the air or atmosphere around us.

The continuous cycling of water in its three forms (solid, liquid and gas) in nature, keeps the total amount of water on the earth constant even when the whole world is using it

Scarcity of Water (or Shortage of Water)

The amount of water recommended by the United Nations (UN) for drinking, washing, cooking and maintaining proper hygiene is a minimum of 50 litres per person per day.

Only some of the people in our country get this minimum amount of water for their daily needs. Millions of people in our country do not get sufficient water.

In some places there is an acute shortage of water, especially during summers. Taps running dry, long queues for collecting water , fights over sharing of water, protest marches and demonstrations for demanding more water from the civic authorities have become a common sight during the summer period.

Most of the towns and cities have water supply systems which are run by the local civic bodies. Water is drawn from nearby rivers, lakes or tube wells. This water is purified and then supplied to all the houses through a network of pipes. Some of the villages in our country also have such water supply systems.

Many villages, however, do not have any water supply systems to supply piped water in their homes. In such villages, people fetch water directly from the source of water like river, lake or well which may be quite far off.

Women and children usually walk several kilometres daily with pitchers on their heads to fetch water for their households.This harms the women as well as the children. Women in villages have to perform a number of household chores and fetching water from far off places adds to their burden of work. The village children suffer because they spend hours in fetching water due to which they cannot attend their school regularly.

Even the urban areas (city areas) face the problem of water shortage, especially during the summer season.

Some of the causes for the shortage of water (or scarcity of water) are :(1) increasing population, (2) growing irrigation requirements of agriculture (3) rapid growth of industries, and (4) mismanagement of water.

A rock which allows water to pass through it is called a permeable rock. Permeable rock is a porous rock (having tiny pores in it). A rock which does not allow water to pass through it is called an impermeable rock. Impermeable rock is a non-porous rock. It is hard rock.