Water — Key Facts
- Water is a renewable resource (hydrological cycle)
- 96.5% of world water is in oceans (saline)
- Only 2.5% is freshwater — most frozen in glaciers
- Groundwater = 0.68% | Rivers/lakes/air = 0.07%
- India: ~4% of world rainfall, ~2.5% of water, ~18% population
- India's rainfall is highly seasonal & uneven
Causes of Water Scarcity
- Growing population — more demand for drinking, farming, industry
- Over-irrigation — water-intensive crops, free/subsidised power
- Industrialisation — huge water & energy needs
- Urbanisation — housing colonies with private pumps
- Falling water table — over-pumping of groundwater
- Water pollution — sewage, effluents make water unusable
Scarcity is mostly human-made — can occur even in water-rich areas due to unequal access & bad management.
Multi-Purpose River Projects
- A dam = barrier across river creating a reservoir
- Serve many purposes at once (multi-purpose)
- Nehru called them "temples of modern India"
- Purposes: irrigation, hydel power, water supply, flood control, navigation, fishery, recreation
- Integrated water-resource management
Major Dams & Rivers
| Dam | River | State |
|---|
| Bhakra-Nangal | Sutlej | Punjab/HP |
| Hirakud | Mahanadi | Odisha |
| Sardar Sarovar | Narmada | Gujarat |
| Nagarjuna Sagar | Krishna | Telangana/AP |
| Tehri | Bhagirathi | Uttarakhand |
| Rana Pratap Sagar | Chambal | Rajasthan |
Hirakud (Mahanadi) is the world's longest dam.
Problems with Dams
- Regulate natural flow — harms aquatic life migration/breeding
- Sedimentation — silt reduces reservoir capacity
- Induced floods — sudden water release, sediment build-up
- Displacement — submerges land/forest, uproots communities
- Social inequality — benefits reach big farmers/industry
- Land degradation — waterlogging & soil salinity
Narmada Bachao Andolan (Medha Patkar) opposed Sardar Sarovar Dam.
Rainwater Harvesting — Traditional
| Method | Region | Feature |
|---|
| Guls/Kuls | W. Himalayas | Diversion channels for farming |
| Tankas | Rajasthan | Underground rooftop rainwater tanks |
| Khadins/Johads | Rajasthan | Inundation channels & check-dams |
| Bamboo drip | Meghalaya | 200-yr-old bamboo pipe irrigation |
Gendathur (Karnataka) — model village for rooftop rainwater harvesting.
Conservation & Management
- Rainwater harvesting — recharge groundwater, store rain
- Recycle & reuse — treated wastewater for industry/gardens
- Efficient irrigation — drip & sprinkler systems
- Prevent wastage — fix leaks, water-saving habits
- Prevent pollution — treat sewage & effluents
- Revive tradition — tanks, johads, watershed development
Important Exam Points — Quick Recall
- 96.5% — share of world water in oceans (saline)
- 2.5% — share of world's freshwater
- "Temples of modern India" — Nehru's term for multi-purpose dams
- Bhakra-Nangal — on Sutlej; Hirakud — on Mahanadi (world's longest dam)
- Sardar Sarovar — on Narmada; opposed by Narmada Bachao Andolan
- Medha Patkar — leader of Narmada Bachao Andolan
- Tankas — underground rooftop water tanks of Rajasthan (Bikaner, Phalodi, Barmer)
- Bamboo drip irrigation — Meghalaya's traditional system
- Gendathur — Karnataka village famous for rooftop harvesting
- Tamil Nadu — first state to make rooftop rainwater harvesting compulsory