3:Water Resources

 Chapter 3:Water Resources 

Textual Questions Answers 

Answer the following question in about 30 words.

i)Explain how water becomes a renewable resource.

Answer: Water is a renewable resource as it is renewed by water cycle or hydraulic cycle itself, where three processes take place as evaporation ,condensation and precipitation. This process of water cycle is never ending and hence water is a renewable resource

ii)What is water scarcity and what are its main causes?

Answer:The shortage of water, as compared to its demand, is called water scarcity. According to Falken Mark, a Swedish Expert, water scarcity occurs when the water availability is less than 1000 m3 per person per day.

Causes of Scarcity:

Low rainfall

Water scarcity occurs in drought-prone areas.

Variation in seasonal rainfall.

Over-exploitation of water.

Excessive use of water.

Unequal access to water.

Great demand due to growing population.

iii)Compare the advantages and disadvantages of multi-purpose river projects.

Answer:Many river valley projects have been started for the purpose of integrated economic and social development of the river basins.

Advantages of multipurpose projects:

Dams are built for irrigation.

They generate electricity.

They provide water.

They help in industrial development.

They help in recreation and navigation.

They help in fish breeding.

Many benefits are obtained simultaneously. So they are called Multi-purpose projects.

Disadvantages of multipurpose projects:

They affect the natural flow of rivers.

This results in poor sediment flow and excessive sedimentation at the bottom of the reservoir.

It results in poorer habitats for aquatic life in the river.

They submerge the existing vegetation and lead to soil decomposition.

It also causes a large-scale displacement of the local communities.

Answer the following question in about 120 words.

i)Discuss how rainwater harvesting in semi-arid regions of Rajasthan is carried out.

Answer: 

Houses in the semi – arid regions of Rajasthan have traditionally constructed tanks for storing drinking water. They are big and are a part of the well-developed rooftop rainwater harvesting system. 

The tanks are constructed inside the main house or the courtyard, and are connected to the sloping roofs of the houses through a pipe. 

The rain falling on the rooftop travels down and is stored in the tanks. 

The first spell of rain is not collected as this water cleans the roof and the pipes.

 The rainwater from the subsequent spells is collected. This water is used till the next rainy season, and is a reliable source of water even after other sources have dried up.

 The tanks also help in cooling the houses as rooms built around them have generally low temperatures due to conduction.

(ii) Describe how modern adaptations of traditional rainwater harvesting methods are being carried out to conserve and store water.

Answer: Modern adaptations of traditional rainwater harvesting include:

In the semi-arid and arid regions of Rajasthan ‘Rooftop rainwater harvesting’ is practiced to store drinking water.

In hills and mountainous regions, people build diversion channels like the ‘guls’ or ‘kuls’ of the Western Himalayas for agriculture. 

In arid and semi-arid regions, agricultural fields were converted into rain fed storage structures that allowed the water to stagnate and moisten the soil like the ‘Khadins’ in Jaisalmer and the ‘Johads’ in other parts of Rajasthan.    

In Gendathur village, Mysore, about 200 households have adopted the rooftop rainwater harvesting method to conserve water.

In Tamil Nadu, it has been made compulsory for all the houses to have rooftop rainwater harvesting structures.

In the flood plains of Bengal, people developed inundation channels to irrigate their fields.    

Bamboo drip irrigation system is also being used in Meghalaya and other states in the North-East of India.