NCERT Environmental Studies (EVS) important notes Part 17 for AEES, KVS, NVS, DSSSB, UPTET, REET, CTET, BTET, MPTET, HTET and All other Teaching Exams

NCERT 

Environmental Studies

 Important Notes

Part 17

 

• 22 March is celebrated as the world water day!
• Jal Hai, To Kal Hai Jal Hai, To Kal Hai
• “If you have water, you can think of the future” “If you have water, you can think of the future”
• 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.
• Year 2003 was observed as the International Year of Freshwater to make people aware of this dwindling natural resource.
• 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. The water that is fit for use is freshwater.
• 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 solid ice, is present as ice caps at the poles of the earth, snow-covered mountains and glaciers. 
• Liquid water Liquid is present in oceans, lakes, rivers, and even underground. 
• The gaseous form is the gaseous 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.
• 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. 
• The upper limit of this layer is called the water table. The water table 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.
• 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.

 

 

DEPLETION OF WATER TABLE

• Water drawn from under the ground gets replenished 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 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.

Increasing population

• 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.
• 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.

 

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 day by day. This results in depletion of water table.

 

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.

 

WATER MANAGEMENT

• Many places a regular supply of water is 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.
• 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.
• 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. 
• Drip irrigation is a technique of watering plants by making use of narrow tubings which deliver water directly at the base of the plant.

 

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. 

 

EFFECT OF WATER SCARCITY ON PLANTS

• 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.

 

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 water-harvesting structures. 

 

 

Important poins to Remember

 

• Water is essential for all living beings. There can be no life without it.
• Water exists in three forms: solid, liquid and vapour. 
• Though water is maintained by the water cycle, yet there is an acute scarcity of water in many parts of the globe. 
• There is an uneven distribution of water. Much of it has resulted from human activities. 
• Rapid growth of industries, increasing population, growing irrigation requirements and mismanagement are some of the causes for water shortage. 
• 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. 
• The need of the hour is that every individual uses water economically. 
• Plants wilt and ultimately dry-up if they are not watered for a few days. 

 

 

Water Cycle 

 

1. Ground Water

2. Evaporation

3. Condensation

4. Cloud

5. Transportation

6. Infiltration

7. Precipitation

 

Forests

• The forest floor provides favourable conditions for them to germinate and develop into seedlings and saplings. Some grow up into trees. He added that branchy part of a tree above the stem is known as the crown of the tree.
• The branches of the tall trees look like a roof over the other plants in the forest. He told them that this is called a canopy.
• All animals, whether herbivores or carnivores, depend ultimately on plants for food.
• Organisms which feed on plants often get eaten by other organisms, and so on. For example, grass is eaten by insects, which in turn, is taken by the frog. The frog is consumed by snakes. This is said to form a food chain:
  Grass→ insects→ frog→ snake→ eagle.
• Many food chains can be found in the forest. All food chains are linked. If any one food chain is disturbed, it affects other food chains.
• Every part of the forest is dependent on the other parts. If we remove one component, say trees, all other components would be affected.
• Mushroom and other micro-organisms feed upon the dead plant and animal tissues and convert them into a dark coloured substance called humus.
•  The micro-organisms which convert the dead plants and animals to humus are known as decomposers.
• Plants release oxygen through the process of photosynthesis. The plants help to provide oxygen for animal respiration. They also maintain the balance of oxygen and carbon dioxide in the atmosphere. That is why forests are called lungs.
• The forest is not just home to plants and animals. Many people also live in the forest. Some of them may belong to different tribes. The forest provides them with food, shelter, water and medicines.
• The dense bushes and the tall grass provide animals with the food and shelter. They also protect them from carnivores that live in the forest.
• By harbouring greater variety of plants, the forest provides greater opportunities for food and habitat for the herbivores. Larger number of herbivores means increased availability of food for a variety of carnivores. The wide variety of animals helps the forest to regenerate and grow.
• Decomposers help in maintaining the supply of nutrients to the growing plants in the forest. Therefore, the forest is a ‘dynamic living entity’ — full of life and dynamic living entity vitality.
• Forests not only help in controlling floods but also help maintain the flow of water in the streams so that we get a steady supply of water. On the other hand, if trees are not present, rain hits the ground directly and may flood the area around it. Heavy rain may also damages the soil. Roots of trees normally bind the soil together, but in their absence the soil is washed away or eroded.
• If forests disappear, the amount of carbon dioxide in air will increase, resulting in the increase of earth’s temperature. 
• In the absence of trees and plants, the animals will not get food and shelter. 
• In the absence of trees, the soil will not hold water, which will cause floods. 
• Deforestation will endanger our life and environment. Think, what we can do to preserve our forests.

 

Important points to remember

• We get various products from the forests surrounding us. 
• Forest is a system comprising various plants, animals and micro-organisms. 
• In a forest, trees form the uppermost layer, followed by shrubs. The herbs form the lowest layer of vegetation. 
• Different layers of vegetation provide food and shelter for animals, birds and insects. 
• The various components of the forest are interdependent on one another. 
• The forest keeps on growing and changing, and can regenerate. 
• In the forest, there is interaction between soil, water, air and living organisms. 
• Forests protect the soil from erosion. 
• Soil helps forests to grow and regenerate.
• Forests are the lifeline for the forest-dwelling communities.
• Forests influence climate, water cycle and air quality.

 

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