- Why a planet whose surface is three-fourths water can still have countries and cities suffering from water scarcity
- What a multi-purpose river project actually does, and the real criticisms raised against big dams
- How ancient India built dams, lakes and tanks centuries before “modern” water management existed
- How rainwater harvesting worked in the past, and how it is being adapted today in many parts of India
1Water: A Renewable Resource
Three-fourths of the earth’s surface is covered with water, but only a small share is freshwater fit for use, mainly from surface run-off and groundwater, both continually renewed through the hydrological cycle.
The hydrological cycle is the continuous circulation of water between the oceans, the atmosphere and the land, through evaporation, precipitation and run-off. The book says that all water moves within the hydrological cycle, ensuring that water is a renewable resource. Renewable does not mean it cannot run short: the book warns that over-exploitation has depleted water resources in several cities.
“Explain how water becomes a renewable resource” is a direct 30-word NCERT exercise question. Answer with the hydrological cycle idea above, not with examples of water use.
This raises an obvious question: if water renews itself and covers most of the planet, why do regions and even entire countries suffer from water scarcity? It is predicted that by 2025, nearly two billion people will be living in absolute water scarcity.
2Water Scarcity and the Need for Conservation and Management
2.1 What Actually Causes Water Scarcity
Water shortage is usually pictured as a low-rainfall, drought-prone problem, like the deserts of Rajasthan. That picture is incomplete: availability does vary with seasonal and annual precipitation, but in most cases scarcity has a different cause altogether.
Water scarcity is a shortage of usable water. The book says that water scarcity in most cases is caused by over-exploitation, excessive use and unequal access to water among different social groups, rather than by low rainfall alone; a large and growing population and polluted water can also cause it.
A region can have ample water resources and still face scarcity (“many of our cities are such examples”): a large and growing population makes greater demands for water, and access to it is unequal. Scarcity can also come from bad quality of water, when abundant water is polluted. A large population needs more water not only for domestic use but also to produce more food; since irrigated agriculture is the largest consumer of water, growing more food over-exploits water resources further, which is why the book calls for drought-resistant crops and dry farming. Post-independence industrialisation and urbanisation add the same pressure: industries are heavy users of water and also need power, much of which comes from hydroelectric power, and most housing societies in cities have their own groundwater pumping devices, so fragile water resources have been over-exploited and depleted in several cities.
Pollution is also a cause of scarcity: the book says that even where there is ample water, much of it may be polluted by domestic and industrial wastes, chemicals, pesticides and fertilisers used in agriculture, making it hazardous for human use.
2.2 Why Conservation and Management Matter
Safeguards health
Protects against water-borne health hazards.
Ensures food security
Irrigated agriculture depends on managed water supply.
Protects livelihoods
Many productive activities depend on continued water access.
Prevents ecological crisis
Over-exploitation and mismanagement degrade natural ecosystems.
2.3 Government Missions for Water Conservation
| Scheme | What it does |
|---|---|
| Jal Jeevan Mission (JJM) | Goal: every rural household gets an assured supply of potable piped water, 55 litres per capita per day, on a long-term regular basis. Source: Economic Survey 2020-21, p.357 |
| Atal Bhujal Yojana (Atal Jal) | Implemented in 8,220 water-stressed Gram Panchayats, across 229 blocks/talukas, 80 districts and 7 states (Gujarat, Haryana, Karnataka, Madhya Pradesh, Maharashtra, Rajasthan, Uttar Pradesh), together holding ~37% of India’s water-stressed blocks. Aims to shift community behaviour from consumption to conservation. Source: Annual Report, Ministry of Jal Shakti, GoI, 2022-23 |
2.4 India’s Ancient Tradition of Water Harvesting
India has built sophisticated hydraulic structures, dams of stone rubble, reservoirs, embankments, irrigation canals, since ancient times, a tradition modern dams simply continue.
Evidence of sophisticated irrigation works has also been found in Kalinga (Odisha), Nagarjunakonda (Andhra Pradesh), Bennur (Karnataka) and Kolhapur (Maharashtra).
Source: Dying Wisdom, CSE, 1997.
3Multi-Purpose River Projects
3.1 What a Dam Is, and How Projects Became “Multi-Purpose”
A dam is a barrier across flowing water that obstructs, directs or retards its flow, often creating a reservoir, lake or impoundment. The word “dam” actually refers to the reservoir, not the structure itself. Most dams have a spillway (or weir), through which water is meant to flow intermittently or continuously.
| Classified by | Categories |
|---|---|
| Structure / material | Timber dams, embankment dams, masonry dams (with several subtypes) |
| Height | Large dams and major dams, or low, medium-height and high dams |
| Intended purpose | The book names this basis but gives no sub-types |
Dams were traditionally built to impound rivers and rainwater that could be used later to irrigate agricultural fields. Today they also generate electricity, supply domestic/industrial water, control floods, and support recreation, navigation and fish breeding, all integrated together, which is why such dams are now called multi-purpose projects, launched after Independence with their integrated water resources management approach and thought of as the vehicle that would lead the nation to development and progress, overcoming the handicap of its colonial past.
Dams are the “temples of modern India”.
Jawaharlal Nehru
The reason the book gives: dams would integrate the development of agriculture and the village economy with rapid industrialisation and the growth of the urban economy.
3.2 Named Multi-Purpose Projects
| River basin | Project | Integrates |
|---|---|---|
| Sutluj-Beas | Bhakra-Nangal project | Hydel power production + irrigation |
| Mahanadi | Hirakud project | Water conservation + flood control |
| Narmada | Sardar Sarovar Dam | Project covers 4 states; irrigation in Gujarat, Rajasthan and Maharashtra (see below) |
On the Narmada river, Gujarat, spread across 4 states: Maharashtra, Madhya Pradesh, Gujarat and Rajasthan. Will provide irrigation to 18.45 lakh hectares across 3,112 villages in 15 districts of Gujarat, and will also irrigate 2,46,000 hectares in Barmer/Jalore (Rajasthan) and 37,500 hectares in Maharashtra’s tribal hilly tract, through lift. 75% of Gujarat’s command area, and all of Rajasthan’s, is drought-prone. Source: Sardar Sarovar Narmada Nigam Ltd.
3.3 The Case Against Multi-Purpose Projects
In recent years, multi-purpose projects and large dams have come under great scrutiny and opposition for a variety of reasons.
Disrupted sediment flow
Damming disrupts a river’s natural flow, causing poor sediment flow and excess sedimentation, resulting in rockier stream beds and poorer habitats for the rivers’ aquatic life.
Fragmented rivers
Fragmented rivers hinder aquatic fauna migration, especially for spawning.
Submerged vegetation
Reservoirs created on the floodplains submerge the existing vegetation and soil, which decompose over a period of time.
The flood-control irony
Dams built to control floods have themselves triggered floods due to sedimentation in the reservoir, and big dams have mostly been unsuccessful in controlling floods at the time of excessive rainfall.
Other observed effects
The book adds that these floods have caused extensive soil erosion, and sedimentation has deprived the flood plains of silt, a natural fertiliser, adding to land degradation. Multi-purpose projects were also observed to induce earthquakes and cause water-borne diseases and pests, and pollution resulting from excessive use of water.
Displacement
The book’s exercise (Q1 ii) gives large-scale displacement and loss of livelihood as an argument against multi-purpose projects.
Irrigation has also changed the cropping pattern of many regions, with farmers shifting to water-intensive and commercial crops. The book says this has great ecological consequences like salinisation of the soil. Include it when you list the criticisms of multi-purpose projects.
3.4 Government Schemes and Inter-State Disputes
The Pradhan Mantri Krishi Sinchayee Yojana ensures access to some means of protective irrigation for all agricultural farms in the country. Its objectives include expanding cultivable area under assured irrigation (“har khet ko pani“), improving on-farm water-use efficiency to reduce wastage, irrigation and other water-saving technologies (“per drop more crop“), and sustainable water conservation practices.
Multi-purpose projects can also cause inter-state conflict: in the Krishna-Godavari dispute, Karnataka and Andhra Pradesh objected to Maharashtra diverting more water at Koyna, reducing downstream flow for their agriculture and industry.
A popular Bhadu song of the Damodar valley narrates the troubles people face when the Damodar floods: the crops are sown, the river has swollen, and the boats cannot sail. The Damodar river is known as the “river of sorrow”.
4Rainwater Harvesting
Rainwater harvesting is the technique of capturing and storing rainwater, often through rooftop structures, for direct use or to recharge groundwater, instead of letting it run off.
Alongside dams and hydraulic structures, people across India had deep knowledge of local rainfall and soil, and developed harvesting techniques suited to their own ecology.
| Region | Traditional technique |
|---|---|
| Western Himalayas (hill regions) | Diversion channels called guls or kuls for agriculture, e.g. a kul leading to a circular village tank in Kaza village |
| Flood plains of Bengal | Inundation channels developed to irrigate fields |
| Arid/semi-arid Rajasthan | Agricultural fields converted into rain-fed storage structures: khadins (Jaisalmer) and johads (elsewhere in Rajasthan) |
| Bikaner, Phalodi, Barmer | Underground tankas in almost every house for storing drinking water, part of a rooftop harvesting system |
A household tanka in Phalodi measured 6.1 m deep, 4.27 m long and 2.44 m wide, connected by pipe to a sloping roof. The first rain was skipped, since it cleans the roof and pipe; later showers were stored until the next rainfall. This water, palar pani, is considered the purest form of natural water; underground rooms were built next to tankas to stay cool.
In western Rajasthan today, rooftop rainwater harvesting is declining because of the perennial Indira Gandhi Canal, though some houses still maintain their tankas since they do not like the taste of tap water.
4.1 Rooftop Rainwater Harvesting: The Gendathur Example
About 200 households in Gendathur village (Mysuru district, Karnataka) installed rooftop rainwater harvesting, earning the village its reputation as “rich in rainwater.” It receives 1,000 mm annual precipitation, with 80% collection efficiency across roughly 10 fillings a year, and each house can collect and use about 50,000 litres annually.
The book’s Fig. 3.4 shows two ways of recharging groundwater: (a) through a hand pump and (b) through an abandoned dugwell.
4.2 Rooftop Harvesting Across India Today
Shillong, Meghalaya
The state capital faces acute water shortage even though Cherapunjee and Mawsynram, 55 km from Shillong, receive the highest rainfall in the world. Nearly every household harvests rooftop rainwater, meeting 15-25% of the household’s total water need.
Thar region, western Rajasthan
Rooftop harvesting is common across towns and villages; rainwater from sloping roofs travels by pipe into an underground tanka (a circular hole in the ground) in the main house or courtyard.
Tamil Nadu
The first state in India to make rooftop rainwater harvesting structures compulsory for all houses, with legal provisions to punish defaulters.
4.3 Bamboo Drip Irrigation, Meghalaya
A 200-year-old system tapping stream and spring water via bamboo pipes. Perennial hilltop springs are diverted by gravity to lower reaches; bamboo channel sections then distribute the flow into branches at the plant site, controlled by adjusting pipe position, and raised high wherever they cross a road. About 18-20 litres enters the system, reducing to just 20-80 drops per minute at each plant’s roots.
- Can I explain water’s renewability, and three real causes of scarcity?
- Can I name Bhakra-Nangal, Hirakud, Sardar Sarovar with their basins, and two disadvantages of such projects?
- Can I describe rainwater harvesting in semi-arid Rajasthan and one modern example?
- Water is renewable through the hydrological cycle, yet by 2025 nearly 2 billion people may face absolute water scarcity
- Scarcity is in most cases caused by over-exploitation, excessive use and unequal access; a growing population and pollution also cause it, not only low rainfall
- Jal Jeevan Mission: 55 litres per capita per day; Atal Bhujal Yojana: 8,220 Gram Panchayats across 7 states
- Ancient hydraulic works: Chandragupta Maurya’s era, Sringaverapura (1st century B.C.), Bhopal Lake (11th c.), Hauz Khas tank (13th-14th c.)
- A dam is a barrier across flowing water; multi-purpose projects integrate irrigation, power, water supply, flood control, recreation, navigation and fish breeding
- Bhakra-Nangal (Sutluj-Beas): power + irrigation; Hirakud (Mahanadi): conservation + flood control; Sardar Sarovar (Narmada): project covering 4 states, irrigating land in Gujarat, Rajasthan and Maharashtra
- Criticisms of big dams: disrupted sediment flow, fragmented rivers, submerged vegetation, floods the dams were meant to control, soil erosion, earthquakes, water-borne diseases and pollution
- Traditional rainwater harvesting: guls/kuls (Himalayas), khadins and johads (Rajasthan), tankas (Bikaner, Phalodi, Barmer)
- Modern examples: Gendathur (Karnataka) rooftop harvesting, Shillong’s paradox despite nearby Cherapunjee/Mawsynram, Tamil Nadu’s compulsory law, Meghalaya’s 200-year-old bamboo drip irrigation