Chapter 3: Water Resources
Water Scarcity and the Need to Conserve
Water is a renewable resource — three-fourths of the earth's surface is covered with it — yet 96.5% of the total volume is in oceans (saline) and only about 2.5% is fresh water. Nearly 70% of this fresh water occurs as ice sheets and glaciers; only a fraction is available as usable ground water and surface water. Water is being renewed through the hydrological cycle, but its availability varies over space and time.
Water scarcity is caused not only by low rainfall but also by over-exploitation, excessive use and unequal access. Its causes include:
- Large and growing population — more water needed for domestic use and to grow more food, so irrigation demand rises.
- Over-exploitation of ground water resources by farmers and industry to expand irrigated area and dry-season agriculture (tube wells and pumps lower the water table).
- Industrialisation and urbanisation — industries are heavy users of water and power, and urban centres with dense populations and lifestyles have added to the demand.
- Deteriorating water quality due to domestic and industrial pollution, making otherwise available water hazardous and unfit for use.
Hence water scarcity may exist even in a region with plenty of water because of bad quality of water.
Multi-purpose River Projects and Integrated Water Resources Management
Dams are barriers across flowing water that obstruct, direct or retard the flow, creating a reservoir. Traditionally, dams were built to impound rivers and rainwater for irrigation; today they are multi-purpose projects where many uses of impounded water are integrated with one another — hence Jawaharlal Nehru proudly called them the "temples of modern India". Purposes include irrigation, electricity generation, water supply, flood control, recreation, inland navigation and fish breeding.
| Multipurpose Project | River | State(s) |
|---|---|---|
| Bhakra Nangal | Satluj–Beas | Punjab / Himachal Pradesh |
| Hirakud | Mahanadi | Odisha |
| Sardar Sarovar | Narmada | Gujarat |
| Tehri | Bhagirathi (Ganga) | Uttarakhand |
| Nagarjuna Sagar | Krishna | Telangana / Andhra Pradesh |
| Rana Pratap Sagar | Chambal | Rajasthan |
| Salal | Chenab | Jammu and Kashmir |
| Tungabhadra | Tungabhadra (tributary of Krishna) | Karnataka / Andhra Pradesh |
Criticism of Multi-purpose Projects
Regulating and damming rivers affects their natural flow, causing poor sediment flow and excessive sedimentation at the reservoir bottom, which harms aquatic life. Dams fragment rivers, making it difficult for aquatic fauna to migrate and spawn.
- The flood plains are deprived of silt; the reservoir submerges the existing vegetation and soil, which decomposes over time.
- Multi-purpose projects and large dams have been the cause of many social movements — the Narmada Bachao Andolan and the Tehri Dam Andolan. Resistance is mainly due to large-scale displacement of local communities, who sacrifice their lands and livelihoods for the greater good of the nation, often without adequate rehabilitation.
- Ironically, dams built to control floods have triggered floods due to sedimentation. Big dams have also been unable to control floods at the time of excessive rainfall (e.g. the release of water during floods in Maharashtra and Gujarat).
- Inter-state water disputes have become common — e.g. objections by downstream states over the Krishna–Godavari dispute and the sharing of Kaveri waters.
Rainwater Harvesting
In the face of the growing scarcity, people have turned to rainwater harvesting — a low-cost, eco-friendly technique. India has a long tradition of water harvesting adjusted to local ecology. Key traditional methods (an important exam table):
| Region | Method | Description |
|---|---|---|
| Hilly / mountainous regions (Himachal Pradesh, Jammu) | Guls / Kuls | Diversion channels built to harvest and carry water for agriculture |
| Rajasthan (Bikaner, Phalodi, Barmer) | Tankas / Kunds | Underground tanks in houses to store rooftop rainwater for drinking |
| Rajasthan, Gujarat (semi-arid) | Khadins & Johads | Structures to store and conserve rainwater and recharge ground water |
| West Bengal (flood plains) | Inundation channels | People developed channels to irrigate their fields |
| Rooftop (widespread traditional practice) | Rooftop rainwater harvesting | Rooftop rainwater led via pipes to an underground tank (tankas); common in Rajasthan and semi-arid regions |
- Gendathur, Karnataka: a village where nearly 200 households built rooftop rainwater harvesting structures and raised their water self-sufficiency.
- Tamil Nadu is the first and only state in India to make rooftop rainwater harvesting structures compulsory for all houses; there are legal provisions to punish defaulters.
- Bamboo drip irrigation (Meghalaya): a 200-year-old system in which water from streams and springs is tapped by bamboo pipes to drip-irrigate plantations.
Map Work (CBSE Prescribed)
Although the theory of this chapter is Periodic-Assessment-only, the following 8 dams ARE prescribed for the Board map question — you must be able to locate and label them on the outline map of India:
- Salal Dam — on the Chenab, Jammu and Kashmir
- Bhakra Nangal Dam — on the Satluj, Punjab / Himachal Pradesh border
- Tehri Dam — on the Bhagirathi, Uttarakhand
- Rana Pratap Sagar Dam — on the Chambal, Rajasthan
- Sardar Sarovar Dam — on the Narmada, Gujarat
- Hirakud Dam — on the Mahanadi, Odisha
- Nagarjuna Sagar Dam — on the Krishna, Telangana / Andhra Pradesh
- Tungabhadra Dam — on the Tungabhadra, Karnataka / Andhra Pradesh