Back to: MBOSE Social Science Class 10

Water which is obtained from surface runoff and groundwater is termed as freshwater. Such water is continually renewed and recharged through the hydrological cycle.

Water is a renewable resource as it gets renewed by water cycle that includes three processes – evaporation, condensation and precipitation. The water that disappears from the surface of the earth due to evaporation comes back in the form of rain. This process of water cycle is never ending which makes it a renewable resource.

Scarcity of water is defined as a situation where there is lack of fresh water resources to meet water demand.

There are two major reasons which are responsible for water scarcity in India. They are

1. Population growth which increases the demand for more water and 
2. Unequal access to it.

The water shortage problem aggravated in post-independence India :

The post independent India witnessed rapid industrialization and urbanization. Large industrial houses consume fresh water resources. Industries, apart from being heavy users of water, also require power to run them. Much of this energy comes from the hydroelectric power. Further, industries also discharge their sewage and effluents into water bodies polluting them resulting into water scarcity.

• Urbanization has also aggravated the problem of water scarcity. Most of our cities are overpopulated. Over population leads to over-utilization of the water resources, and also pollutes the existing resources.
• Housing societies and colonies in the cities and towns have their own ground water pumping devices to meet their water needs. The practice of ground water pumping also affects the level of water table.
• The fragile water resources are being over-exploited and have caused their depletion in several of these cities.

We need to conserve and manage our water resources due to following reasons:

• To safeguard ourselves from health hazard.
• To ensure food security.
• To prevent degradation of our natural ecosystems.
• Over exploitation and mismanagement of water resources will impoverish this resource and will cause ecological crisis.

A dam is a barrier across flowing water that obstructs, directs or retards the flow, often creating a reservoir, lake or impoundment. Based on structure or material used, dams are classified as timber dams, embankment dams or masonry dams, with several sub-types

The Advantages of Dam are:

1.Large Dams ensure storage of water for irrigation purposes and also for generating electricity.

• Canals leading from these dams transfer large amount of water over long distances and help in supplying water to far off villages for irrigation and for used by people for drinking bathing and other use.
• Water from dam is supplied to the people in towns and cities through pipelines after suitable treatment.
• Can prevent uncontrolled flooding.
• Reduces consumption of fossil fuels for electricity production
• When in use, electricity produced by dam systems do not produce green house gases.
• They do not pollute the atmosphere.
• The lake that forms behind the dam can be used for water sports and leisure / pleasure activities. Often large dams become tourist attractions in their own right. The lake’s water can be used for irrigation purposes.

Inter-state water disputes are disagreements on the sharing of water and other resources of rivers and other water bodies among State Governments. The Interstate River Water Disputes Act, 1956 (IRWD Act) is an Act of the Parliament of India enacted under Article 262 of Constitution of India on the eve of reorganization of states on linguistic basis to resolve the water disputes that would arise in the use, control and distribution of an interstate river^[ or river valley. Article 262 of the Indian Constitution provides a role for the Central government in adjudicating conflicts surrounding inter-state rivers that arise among the state/regional governments.  This Act further has undergone amendments subsequently and its most recent amendment took place in the year 2002.

Examples of interstate water disputes are

1. The Kaveri river water dispute is among Tamil Nadu, Karnataka, Kerala and Puducherry.
2. The Krishna – Godavari water dispute is among Maharashtra, Andhra Pradesh and Karnataka.
3. The Ravi – Beas rivers water dispute is between Punjab and Haryana.
4. The Yamuna river water dispute is between Haryana and Uttar Pradesh.

Suggest interstate water disputes can be resolved?

Nagaland is the only State in India with least number of rivers.  Nagaland has total 3 rivers in the state.

Rainwater harvesting is the process of accumulation and storage of rainwater for reuse rather than allowing it to runoff. Rainwater harvesting is a sustainable process that helps in preserving water for future needs. Water scarcity is a major concern in today’s scenario. The process of rainwater harvesting is a good way to conserve water.

The different methods of rainwater harvesting include:

• Rooftop rainwater harvesting.
• Surface runoff harvesting.
• First, flush.
• Transportation.
• Catchment.
• Filter.

Advantages of implementing rain-water harvesting:

1. Reduced Water Bills – Rainwater harvesting systems are cost-effective, provide high-quality water, lessen dependence on wells and are considerably easy to maintain since they are not utilized for drinking, cooking or other sensitive uses. The all-around expenditures used in setting up harvesting methods are much cheaper compared to other purifying or pumping means. The cost of recharge to the subsurface reservoir is also lower than the surface reservoirs.
2. Ecological benefit – Storing water underground is environment-friendly. The ecological benefits of rainwater harvesting are immense. It minimizes the impacts of flooding by funneling the off water into large tanks for recycling and helps reduce the load placed upon drainage systems. No land is wasted for storage purpose and no population displacement is implicated therefore, groundwater is not directly exposed to evaporation and pollution. Additionally, it helps minimize the possibility of rivers drying up.
3. Reduces erosion and flooding around buildings – It reduces soil erosion and flood hazards by collecting rainwater and reducing the flow of storm water to prevent urban flooding. Most buildings that utilize rainwater harvesting systems have a built-in catchment area on top of the roof, which has a capacity of collecting large volumes of water in case of rainstorms.
4. An adequate means for Irrigation purpose – Harvesting rainwater allows the collection of large amounts of water and mitigates the effects of drought. Most rooftops provide the necessary platform for collecting water. Rainwater is mostly free from harmful chemicals, which makes it suitable for irrigation purposes.
5. Reduces demand on Ground Water – Another vital benefit is that it increases the productivity of aquifer resulting in the rise of groundwater levels and reduces the need for potable water. It is extremely essential, particularly in areas with low water levels.

Disadvantages of Rain water Harvesting:  

1. Unpredictable Rainfall:  Rainfall is hard to predict, and sometimes little, or no rainfall can limit the supply of rainwater.  It is not advisable to depend on rainwater alone for all your water needs in areas where there is limited rainfall. Rainwater harvesting is suitable in those areas that receive plenty of rainfall. If rain is unpredictable, the use of a rainwater harvesting system can be critical to capturing the rain when it does fall.
2. Initial High Cost:  Depending on the system’s size and technology level, a rainwater harvesting system may cost anywhere between $200 to $2000 and benefit from it cannot be derived until it is ready for use. Like solar panels, the cost can be recovered in 10-15 years, which again depends on the amount of rainfall and sophistication of the system.
3. Regular Maintenance: Rainwater harvesting systems require regular maintenance as they may get prone to rodents, mosquitoes, algae growth, insects and lizards. They can become breeding grounds for many animals if they are not properly maintained.
4. Certain Roof Types may Seep Chemicals or Animal Droppings: Certain types of roofs may seep chemicals, insects, dirt or animals droppings that can harm plants if it is used for watering the plants.
5. Storage Limits: The collection and storage facilities may also impose some kind of restrictions as to how much rainwater you can use. During the heavy downpour, the collection systems may not be able to hold all rainwater, which ends in going to drains and rivers. Rainwater collected during the first rainy season is generally not needed by plants until the dry season though it can be used for other household purposes. However, once the catchment is full, it cannot take advantage of future rains.

There are two major techniques of rainwater harvesting.

1. Surface runoff harvesting: In this method, rainwater flows away as surface runoff and can be stored for future use. Surface water can be stored by diverting the flow of small creeks and streams into reservoirs on the surface or underground. It can provide water for farming, for cattle and also for general domestic use. Surface runoff harvesting is most suitable in urban areas.  Rooftop rainwater/storm runoff can be harvested in urban areas through:
2. Recharge Pit
3. Recharge Trench
4. Tubewell
5. Recharge Well
   1. Groundwater recharge: Groundwater recharge is a hydrologic process where water moves downward from surface water to groundwater. Recharge is the primary method through which water enters an aquifer. The aquifer also serves as a distribution system. The surplus rainwater can then be used to recharge groundwater aquifer through artificial recharge techniques.  Rainwater in rural areas can be harvested through:
6. Gully Plug
7.  Contour Bund
8. Dugwell Recharge
9. Percolation Tank
10. Check Dam/Cement Plug/Nala Bund
11. Recharge Shaft

Although rainwater harvesting measure is deemed to be a desirable concept since the last few years, it is rarely being implemented in rural India. Different regions of the country practiced a variety of rainwater harvesting and artificial recharge methods. Some ancient rainwater harvesting methods followed in India which includes Madakas, Ahar Pynes, Surangas, Taankas, etc.

Examples of Traditional water harvesting system in India

Trans-Himalayan Region : Zing -Tanks for collecting water from melted ice in Ladakh.

Western Himalayas: Kul -Water channels in mountain areas of Jammu, Himachal Pradesh. Naula -Small ponds in Uttaranchal.

Eastern Himalayas :

• Northeastern Hill Ranges :
  Apatani system -Terraced plots connected by inlet and outlet channels in Arunachal Pradesh.
  Zabo -Impounding runoff in Nagaland
  Bamboo drip irrigation – Water from streams in the hills is brought to the plains via bamboo pipes for drip irrigation in Meghalaya
• Brahmaputra Valley
• Dongs – Ponds in Assam
• Dungs or Jampois – small irrigation channels linking rice fields to streams in the Jalpaiguri district of West Bengal

Indo-Gangetic Plain

• Dighis -Small square or circular reservoir fed by canals from rivers in Delhi
• Baolis – secular structured stepwells from which everyone could draw water and use for washing and bathing.

Thar Desert

• Baoris / Bers -Community wells in Rajasthan
• Tankas -Underground tank Bikaner in Rajasthan
• Kund – a circular underground well; having a saucer-shaped catchment area that gently slopes towards the center where the well is situated.

Central Highlands – Johads -Earthen check dams in Alwar district, Rajasthan

Rainwater Harvesting In Arunachal: Arunachal Pradesh water resources department has executed demonstrative projects on rooftop rainwater harvesting and artificial recharge to groundwater under the cent percent central sector scheme “Groundwater management and regulation” during the 11th Five Year Plan, covering 235 projects in 11 districts. The districts included Tawang, West and East Kameng, Papum Pare, Kurung Kumey, Lower and Upper Subansiri, East and West Siang, Lower Dibang Valley, Anjaw, Miao (Changlang), Tirap and Longding. Out of the above, 100 projects were implemented in government schools, hospitals, primary health centers, office buildings, Circuit houses, and inspection bungalows. These projects were successfully executed and handed over to the user agencies for operation, maintenance and its utilization for various water needs. The first successful projects carried out by the Arunachal Pradesh water resources department was in Ruksin in East Siang district during 2002-03.

The Apatani’s System – a wet rice cultivation cum fish farming system practiced in elevated regions of about 1600 m and gently sloping valleys. This system harvests both ground and surface water for irrigation. It is practiced by Apatani tribes of Ziro in the Lower Subansiri district of Arunachal Pradesh. In the Apatani’s system, valleys are terraced into plots divided by 0.6 meters high earthen dams which are then supported by bamboo frames. All plots have an inlet and outlet on opposite sides. The inlet of low lying plot functions as an outlet of the high lying plot. Deeper channels connect the inlet point to the outlet point. The terraced plot can be flooded or drained off with water by opening and blocking the inlets and outlets as and when required. The stream water is tapped by constructing a wall of 2-4 m high and 1 m thick near forested hill slopes. This is conveyed to agricultural fields through a channel network.

How rainwater harvesting in semi-arid regions of Rajasthan is carried out: In the semi-arid and arid regions of Rajasthan, almost all the houses have traditionally constructed tanks for storing drinking water. They are large and are a part of the well-developed rooftop rainwater harvesting system. They are built inside the main house or the courtyard, and are connected to the sloping roofs of the houses through a pipe. Rain falling on the rooftops flows down through the pipe and gets stored in these tanks. The first spell of rain is not collected as it cleans the roofs and the pipes. The rainwater from the next showers is then collected. The rainwater can be stored in the tanks is considered as the most reliable source of water particularly in summers when most of the water sources are dried up. This stored water can be used till the next rainy season.

How modern adaptations of traditional rainwater harvesting methods are being carried out to conserve and store water: 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.  

Rain water harvesting as a good way to solve drinking water problem in certain areas and replenish the ground.

• Rainwater harvesting is a type of harvest in which the rain drops are collected and stored for the future use, rather than allowing it to run off. Rainwater can be collected from rivers or roofs and redirected to a deep pit, aquifer, a reservoir with percolation, or collected from dew or fog with nets or other tools.
• Having a source of water can also reduce dependence on municipal sources in case the water becomes contaminated.
• Another vital benefit is that it increases the productivity of aquifer resulting in the rise of groundwater levels and reduces the need for potable water. It is extremely essential, particularly in areas with low water levels.