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Notes – Water Resources

Water is an Important Natural Resource

Water is a very important natural resources available on earth. Its utilty for life of humans, animals and vegetation make it a basic need of living things on earth. Our earth is unique because of availability of water on it.

Availability of Water on earth

Renewable Resource: Water is a renewable resource and replenished or renewed through hydrological cycle.

Hydrological cycle: It is the journey of water cycle that remains in a continuous flux. The total quantity of water present on earth remains constant. Water only changes its form from solid to liquid to gas and back to liquid. This is known as the hydrological cycle.

Fresh water:

• Only 3 percent of the total water on earth is freshwater.
• One-third of this freshwater is inaccessible to human beings.
• Only two-thirds of the freshwater is accessible to human beings and fit for consumption.
• The freshwater available to humans is obtained from surface run-off and recharge of groundwater.

Utility of Water

• Water is a basic need of life for survival of living things.
• Used for domestic purposes – cooking, drinking, washing.
• Used for agricultural purposes.
• Used in manufacturing industries.
• River and oceans are used for navigation.
• Used for hydro electricity production.

Water Scarcity

Q. Hint: What are the causes and effects of water scarcity?

• The demand for water has increased immensely over the years, but the supply of freshwater remains constant.
• This has led to an alarming situation of water scarcity in many parts of the world.
• The amount of water available varies from one region to another due to variations in annual precipitation.

Quantitative Causes of Water Scarcity

• Over-exploitation or misuse of water is one of the major reasons for water scarcity.
• Population growth, industrialisation, expanding agriculture, unequal access to water resources are a few reasons why the water demand has gone up in recent years.
• Irrigation facilities meant to grow crops in the dry and semi-arid regions put a heavy demand on water resources.
• Industrialisation after independence has put immense pressure on freshwater resources and worsened the situation.
• To meet the energy requirements of urbanisation and industrialisation, many hydroelectric power plants have been set up that derive energy from water.
• Personalised pumping devices in urban residential buildings and individual farmer’s wells and tube wells have aggravated water scarcity by lowering the groundwater level.

Qualitative Causes of Water Scarcity

• The availability of a sufficient amount of water does not necessarily meet the demands of the populations in a region.
• The bad quality of water due to pollution is another reason for water scarcity.
• Pollution of water is caused by domestic waste, industrial waste, synthetic chemicals, and fertilizer in agriculture.

Steps to Conserve Water

• We must use water resource wisely.
• It is necessary to conserve water resources to protect us from health hazards, diseases, ensure food security, and protect our ecosystems.
• Revolutionization of agricultural practices is necessary. Drought resistance crops and dry farming techniques are gaining popularity among farmers.
• Reduce, reuse and recycle is a motto to conserve water.
  • Reduce the amount of water needed for each activity. Avoid its wastage.
  • Reuse water for more than one purpose when possible. For example, water used to wash vegetables can be reused to water the plants.
  • Processes to recycle water, such as desalinisation, is very expensive. In certain parts of the world, this process is being used to fight water scarcity.

• An awareness should prevail that exploitation of water resources would endanger human life in future.

Hydraulic Structures

Hydraulic Structures

• Hydraulic structures are constructed to store flowing water or reduce the speed of its flow or redirect its path.
• Such structures have been constructed since ancient times to conserve water.
• Examples of such water structures are:
  • Dam: A wall that acts as a barrier against the flow of water. The wall either obstructs, directs, or slows down the flow of water.
  • Stone rubble: Stones of irregular shape, size, and texture are used as a filling to obstruct the flow of water.
  • Reservoir or lake: These are either formed naturally or created artificially by humans. These are large water bodies used as a means of water supply.
  • Embankment: An artificial wall or bank is raised above the surrounding areas to stop flooding.
  • Canal: An artificial waterway that allows the passage of boats and ships from one place to another.

Hydraulic Structures in Ancient India

Hydraulic structures were constructed in ancient times. A few examples of hydraulic structures in ancient India are:

1. A well-developed water harvesting system was constructed during the first century BCE in Srigaverapura near Prayagraj to channelise the floodwater of river Ganga.
2. Dams, lakes, and irrigation systems were constructed during the rule of Chandragupta Maurya.
3. Old, well-planned irrigation works in Odisha, Andhra Pradesh, Karnataka, and Maharashtra are also counted under the hydraulic structures of ancient India.
4. During the 11th century, the largest artificial lake of its time was built in Bhopal.
5. Construction of Hauz Khas tank in Delhi by Iltumish is also noted for its water supply to the Siri Fort area.

Multipurpose Projects

Q. Hint: What are the merits and demerits of multipurpose projects?

What are Dams?

• A dam is a wall or a barrier built across flowing water.
• The primary purpose of a dam is to obstruct, direct or retard the flow of water.
• Dams are used to create reservoirs of water or lakes.
• Dams can be classified on the basis of structure and height.
• On the basis of structure, dams are timber dams, embankment dams, or masonry dams and their subtypes.
• On the basis of height, dams are large dams and major dams or alternatively low dams, medium height dams, and high dams.

How Do Dams Help Conserve Water?

• Dams were used to collect and store river and rainwater for future use.
• In olden times, water from dams was mainly used for irrigation in agricultural fields.
• Today, dams are used for various purposes such as:

1. Irrigation
2. Generation of electricity
3. Water supply for domestic and industrial use
4. Flood control
5. Recreation (boating, water sports, etc.)
6. Inland navigation (water transport)
7. Fish breeding (pisciculture)

Dams as Multipurpose Projects

• Dam water is used for more than one purpose, and thus dams are called multipurpose projects.
• For example:
  • Bhakra Nangal dam on the Satluj Beas river basin is used for both irrigation and hydel power generation.
  • Hirakund Project on Mahanadi basin helps flood control in the adjoining areas and conserves water for future use.

Multipurpose Projects after Independence

• After independence, multipurpose projects were launched with an integrated water management approach.
• Integrated water resource management (IWRM) is a process to develop land and water resources to maximise economic and social welfare, keeping in mind the sustainability of present ecosystems.
• With this approach, dams are considered as a means for the overall development of the nation.

Dams As Temples of Modern India

• Jawaharlal Nehru had said that dams were the temples of modern India.
• He referred to dams as temples because he could foresee that the construction of dams would help in the development of agriculture.
• This, in turn, would help industrialisation and growth in urban and village economies.

Opposition of Multipurpose Projects

Multipurpose projects are facing opposition in recent times from local people for various reasons:

1. Obstruction in the natural flow of the river
2. Poor sedimentation flow
3. Excessive sedimentation on the riverbed
4. Deterioration of habitats of aquatic animals
5. Difficulty in migration of aquatic animals
6. Decomposition of vegetation in floodplains

Multipurpose Projects and Environmental Movements

• Multipurpose projects have caused harm to the environment.
• Opposition to various projects has come up, such as Narmada Bachao Andolan and Tehri Dam Andolan.
• Multipurpose projects have caused the large-scale displacement of communities.
• Local people had to suffer and sacrifice their land, livelihood, and access to resources for benefits accrued to others.
• Tribal communities are worst affected by dam projects.
• Industrialists, landowners, large farmers are among those who benefit from such projects.
• Narmada Bachao Andolan is a movement against the construction of the Sardar Sarovar Dam built across the Narmada River in Gujarat.

Impact of Multipurpose Projects

Dams have played a positive role in the economic development of India. The construction of dams has facilitated irrigation in many parts of the country.

But there are many detrimental effects also as listed below.

• With the help of irrigation, farmers shifted to the production of water-intensive and commercial crops. Such practices by farmers had an adverse impact on the quality of the soil, causing its salination.
• Multipurpose projects have increased the gap between the rich and the poor by providing unequal access to water resources.
• These projects have also created conflicts among people. For example, Sabarmati basin farmers protested because urban areas were granted more water supply.
• Such projects are also the cause of interstate disputes regarding the sharing of costs and benefits of the projects.

Failure of Multipurpose Projects in Achieving Their Aims

(i) Many multipurpose projects were not able to achieve the aims for which they were constructed. In many instances, these projects had adverse effects such as:

1. Instead of preventing floods, they led to floods upstream due to heavy sedimentation.
2. The release of dam water during heavy rains also led to floods downstream—for example, the floods in Maharashtra and Gujarat in 2006.
3. Obstruction of the flow of sediments results in degradation of the surrounding land as plains are deprived of the natural fertiliser (silt) deposited by the river.

(ii) Other effects of multipurpose projects were:

1. Earthquakes
2. Waterborne diseases
3. Pollution due to overuse and misuse of water

Water Harvesting

Q. Hint: What were the different traditional water harvesting systems in India?

Water Harvesting

• Water harvesting is collecting rainwater and storing it for future use before it is lost as surface runoff.
• Water harvesting has been in practice since ancient times.
• Ancient people had good knowledge of rainfall and soil types, which they used to develop a range of water harvesting techniques.
• They used to harvest rainwater, river water, groundwater, and floodwater using simple techniques to meet their future need for water.
• The methods that were used by the ancient people to harvest water were environment-friendly.

Need for Water Harvesting

• To restore groundwater levels.
• To increase infiltration of rainwater in the subsoil to improve its moisture content.
• To increase agricultural produce of the area.
• To enhance the growth of vegetation in the area.

Traditional Methods of Water Harvesting

Various traditional water harvesting techniques are as follows:

1. Creating diversion channels like guls and kuls
2. Rooftop harvesting
3. Khadins and johads
4. Inundation channels
5. Tankas
6. Kuis or beris
7. Vav or bavadi

Guls and kuls

• Guls and kuls are channels constructed in hilly areas.
• These channels collect rainwater and function as irrigation canals.
• Such channels are commonly used in the western Himalayas for agriculture.

Rooftop harvesting

• In this method, rainwater is collected from the roofs of houses or roof catchments and stored in reservoirs.
• The reservoirs can be above or under the ground.

Khadins and Johads

• Agricultural fields are used for storing rainwater. They are known as johads in some parts of Rajasthan and khadins in Jaisalmer.
• The water is allowed to stand in these fields, which moistens the soil.

Inundation channels

• Inundation channels are long canals constructed mainly from rivers.
• They carry excess river water to agricultural fields during heavy rains and floods.
• Such channels are commonly constructed in the flood plain of West Bengal.

Tankas

• Tankas are among the best traditional methods to harvest rainwater.
• Tankas are like rooms built inside the main house or in the courtyard.
• The roof of the house is connected through pipes to these tankas that store rainwater.
• Tankas are also used for cooling effects. Underground rooms are constructed adjoining tankas to enjoy this cooling effect.

Kuis or beris

• Kuis or beris are pits dug in the catchment areas of rivers.
• They are common in the arid and semi-arid regions of Rajasthan.
• These pits collect water, which then percolates in the soil.
• The water collected by this method is known as the paar system.

Vav or bavadi

• Stepwells are known as vav in Gujarat and bavadi in Rajasthan.
• Vav or bavadi collect and store rainwater.
• The water stored is used for human consumption.

Rainwater Harvesting

Q. Hint: Why is there a need to develop rainwater harvesting system in India?

Conservation of water

• Water is a vital natural resource and the basis of life on earth.
• Since the total amount of water on earth is unchanging and keeps moving in a cyclic manner, water can be used repeatedly after purification.
• Water harvesting is very useful socio-economically and environmentally.
• It offers an alternative to the multipurpose dam projects with their adverse effects.
• Rainwater harvesting was practiced in ancient times, too, with the help of hydraulic structures.
• Since ancient people were aware of -rainwater regimes and soil types, they developed different techniques to harvest rainwater, groundwater, river water, floodwater, and other sources.

Rainwater Harvesting

Rainwater harvesting is a method used to collect and store rainwater to meet the need of living beings. This method of water harvesting is very economical in a developing country like India.

Need for Rainwater Harvesting

Rainwater harvesting is very successful in many parts of the country. Rainwater harvesting is needed:

1. To overcome the shortage of surface water
2. To recharge groundwater levels
3. To make water available, especially in arid and semi-arid regions during summers
4. To increase infiltration of rainwater deep into the soil to provide adequate moisture to the soil
5. To improve the quality of groundwater through filtration
6. To improve the vegetation cover of the area

Rainwater Harvesting Techniques

• People built diversion channels like the ‘guls’ or ‘kuls’ of the Western Himalayas for agriculture in hill and mountainous regions.
• ‘Rooftop rainwater harvesting’ is commonly practiced to store drinking water, particularly in Rajasthan.
• In the flood plains of Bengal, people developed inundation channels to irrigate their fields.
• In arid and semi-arid regions, agricultural fields were converted into rain-fed storage structures that allowed the water to stand and moisten the soil, such as ‘khadins’ in Jaisalmer and ‘Johads’ other parts of Rajasthan.
• The tankas are part of the well-developed rooftop rainwater harvesting system and are built inside the main house or the courtyard. This is mainly practiced in Rajasthan, particularly in Bikaner, Phalodi, and Barmer areas for saving the rainwater. Many houses constructed underground rooms adjoining the ‘tanka’ to beat the summer heat to keep the room cool.

Rainwater Harvesting in Other States

• Rainwater harvesting is also practiced in Shillong, Meghalaya, and Karnataka.
• Almost every house in Mysuru in Karnataka has a rainwater harvesting system.
• This place has an 80 percent efficiency of harvesting rainwater.
• Tamil Nadu is the first state to make rainwater harvesting compulsory. Defaulters face legal punishment in this state.
• Bamboo drip irrigation system is practiced in Meghalaya.