BharatNotes Why this chapter matters for UPSC: Water — its distribution, conservation, and management — is a perennial GS3 topic. This chapter's science (states, water cycle, anomalous expansion) directly connects to India's water stress, Himalayan glacier retreat, Jal Jeevan Mission, river interlinking, groundwater depletion, and the politics of water-sharing. GS1 Geography covers the hydrological cycle and monsoon.
PART 1 — Quick Reference Tables
| Phase Change | Process | Temperature (at sea level) | Heat Change |
|---|---|---|---|
| Melting | Solid → Liquid | 0°C | Absorbs heat |
| Freezing | Liquid → Solid | 0°C | Releases heat |
| Evaporation | Liquid → Gas | Any temperature (surface) | Absorbs heat |
| Boiling | Liquid → Gas | 100°C (sea level); ~84°C at 6,400 m | Absorbs heat |
| Condensation | Gas → Liquid | Below dew point | Releases heat |
| Sublimation | Solid → Gas (directly) | Below melting point | Absorbs heat |
| Water Distribution (Global) | Percentage |
|---|---|
| Saltwater (oceans, seas) | 97.5% |
| Freshwater (total) | 2.5% |
| — In glaciers and ice caps | 68.7% of freshwater |
| — Groundwater | 30.1% of freshwater |
| — Surface water (rivers, lakes) | < 1% of freshwater |
| India Water Indicator | Figure |
|---|---|
| Annual precipitation | ~4,000 BCM/year |
| Utilisable water | ~1,123 BCM/year |
| Per capita water availability | ~1,486 m³/year (below 1,700 stress threshold) |
| Rural tap water coverage (JJM) | ~78% by March 2025 |
| Wastewater treated | ~44% only |
| Surface water polluted | ~70% |
PART 2 — Detailed Notes
Three States of Water
Water (chemical formula H₂O) exists in three states depending on temperature and pressure:
- Solid: Ice, snow, hail, frost, glaciers, permafrost. Water molecules locked in a rigid crystal lattice.
- Liquid: Water, dew, rain, clouds (liquid droplets), fog. Molecules move freely but stay close.
- Gas: Water vapour, steam. Molecules move rapidly and spread out. Water vapour is invisible — "steam" you see is actually tiny liquid droplets.
All three states are chemically identical (H₂O). Changes between states are physical changes — no new substance is formed.
Phase Changes in Detail
Boiling point changes with altitude: At higher altitudes, atmospheric pressure is lower, so water boils at a lower temperature.
- Sea level: 100°C
- Darjeeling (~2,000 m): ~93°C
- Leh (~3,500 m): ~88°C
- Siachen Base Camp (~6,400 m): ~84°C
Consequence: Food takes longer to cook at high altitude because water boils at a lower temperature, reducing the cooking temperature. This is why pressure cookers are essential in the hills — they increase pressure and raise the boiling point.
Sublimation applications:
- Freeze-drying (lyophilisation): Food and pharmaceuticals are frozen, then water is sublimed out under vacuum. Preserves flavour, nutrition, and extends shelf life (space food, military rations, coffee powder).
- Dry ice: Solid CO₂ sublimates; used in food transport and special effects.
- Removal of frost from aircraft wings using de-icing (prevents sublimation from solid state).
Anomalous Expansion of Water
Anomalous expansion: Most substances contract (get denser) as they cool. Water does the opposite between 4°C and 0°C — it expands on freezing.
- Water is densest at 4°C (density ~1.0 g/cm³).
- Ice has density ~0.92 g/cm³ — less dense than liquid water.
- Therefore, ice floats on water.
Ecological significance: In winter, surface water of lakes cools to 4°C and sinks (it's densest). Below 4°C, water becomes less dense and stays at the top. The surface freezes into ice, which acts as an insulating layer. The liquid water below stays at ~4°C, allowing aquatic life (fish, microorganisms) to survive. Without this unique property, entire water bodies would freeze solid and aquatic ecosystems would collapse.
Engineering significance: Burst water pipes in winter — water expands when it freezes, cracking pipes. This is a major infrastructure problem in cold regions (Himalayan towns, North America, Europe).
The Water Cycle (Hydrological Cycle)
Steps of the water cycle:
- Evaporation: Solar energy heats surface water (oceans cover 71% of Earth's surface; oceans contribute ~86% of total evaporation). Water vapour rises.
- Transpiration: Plants release water vapour through stomata in leaves. Evaporation + Transpiration = Evapotranspiration (ET). Forests are critical for ET — deforestation disrupts local water cycles.
- Condensation: Rising water vapour cools at altitude and condenses into tiny droplets around dust/pollen particles (condensation nuclei), forming clouds.
- Precipitation: Water falls as rain, snow, sleet, or hail depending on temperature.
- Surface runoff: Water flows over land into rivers and streams.
- Infiltration: Water seeps into soil and recharges groundwater (aquifers).
- Return to oceans: Rivers carry water back to the sea, completing the cycle.
Solar energy drives the entire cycle. The water cycle is also a heat redistribution mechanism — latent heat absorbed during evaporation is released during condensation, moderating global temperatures.
UPSC GS3 — Environment: India's Water Cycle and Monsoon
India receives ~4,000 BCM (billion cubic metres) of precipitation annually, mostly from the Southwest Monsoon (June–September). Only ~1,123 BCM is utilisable (rest lost to evaporation, flooding, seawater mixing).
Key water cycle disruptions in India:
- Deforestation: Reduces transpiration and local cloud formation; increases surface runoff and floods.
- Urbanisation: Impervious surfaces (concrete) reduce infiltration, causing flash floods and groundwater depletion.
- Glacier retreat: Himalayan glaciers (called the "Third Pole" or "Water Towers of Asia") feed 13 major rivers including the Ganga, Indus, and Brahmaputra. IPCC AR6 warns of accelerated melting under 1.5°C–2°C warming scenarios, threatening dry-season river flows on which 500+ million people depend.
Global and India Water Distribution
UPSC GS3 — Water Conservation and Management
Global picture:
- 97.5% of Earth's water is saltwater (oceans). Only 2.5% is freshwater.
- Of that freshwater: 68.7% locked in glaciers/ice caps (inaccessible); 30.1% groundwater; < 1% accessible surface water (rivers, lakes).
- Freshwater is effectively a non-renewable resource at human timescales — aquifers take thousands of years to recharge.
India's water stress:
- Per capita water availability: ~1,486 m³/year (2021 estimate). Below the international water stress threshold of 1,700 m³/person/year.
- India ranks 13th most water-stressed country (WRI Aqueduct 2019).
- Over-extraction of groundwater: India extracts ~25% of global groundwater — the highest in the world. States like Punjab, Haryana, Rajasthan face critical groundwater depletion.
Government responses:
- Jal Jeevan Mission (JJM, 2019): Provide tap water connections to every rural household by 2024. As of March 2025, ~78% of rural households covered. Budget: ₹3.6 lakh crore.
- Atal Bhujal Yojana: Sustainable groundwater management in 7 water-stressed states.
- NMCG (Namami Gange, 2015): Rejuvenate River Ganga; budget ₹20,000 crore; focus on sewage treatment, industrial effluent control, afforestation.
- Ken-Betwa River Interlinking Project: India's first river interlinking project; approved 2021; cost ₹44,605 crore. Links Ken River (MP) to Betwa River (UP) to transfer surplus water to water-deficit areas. Controversies: displacement of tribals, diversion of Panna Tiger Reserve forest land, ecological concerns about Ken river dolphin habitat.
[Additional] 8a. Jal Jeevan Mission 2.0 — The Har Ghar Jal Mission Extended to 2028
The chapter mentions JJM at ~78% rural tap water coverage. What is missing is the most policy-critical update: the Cabinet extended JJM to December 2028 as JJM 2.0 (March 2026), because ~4 crore rural households still lacked tap connections beyond the original 2024 deadline. JJM 2.0 also introduces Har Ghar Jal certification — a quality-verification standard — and shifts focus from pipe-laying to sustainable water service delivery.
Jal Jeevan Mission — Key Terms:
| Term | Meaning |
|---|---|
| Functional Household Tap Connection (FHTC) | A tap connection at the household level delivering at least 55 litres per capita per day (lpcd) of safe water — the unit JJM measures |
| Har Ghar Jal | "Water to every home" — the goal of JJM; a village/gram panchayat is declared "Har Ghar Jal" when every household AND every public institution (school, anganwadi) has a functional tap |
| Har Ghar Jal Certification | When a village GP verifies through local resolution (at a gram sabha) that every household has safe drinking water; 2.12 lakh villages certified by early 2026 |
| AT&C losses in water | Unlike electricity, water supply systems lose water through leakages, unmetered connections, theft — JJM 2.0 tracks "Non-Revenue Water" (NRW) reduction |
| Field Testing Kit (FTK) | Simple water quality test kit distributed to trained women in villages; tests for coliform, pH, nitrate, iron, turbidity — decentralised quality surveillance |
The water access-quality chain:
- Source (borewell, canal, river) → 2. Treatment plant (to remove contamination) → 3. Storage tank (overhead reservoir) → 4. Distribution pipeline → 5. Household tap → 6. Quality testing (FTK) → 7. Consumer Each step is a potential failure point; JJM 2.0 focuses on sustainability = ensuring all 7 steps function together, not just step 4-5.
[Additional] Jal Jeevan Mission Status and 2028 Extension (GS2 — Governance / Social Justice / GS3 — Environment):
JJM Progress (February 2025):
- Tap connections provided: 15.44 crore rural households (out of 19.36 crore total)
- Coverage percentage: 79.74% (February 2025, PIB)
- Remaining gap: ~4 crore households without tap connections — primarily in UP, Bihar, Rajasthan, MP (states with large rural populations and difficult hydrogeology)
- 11 States/UTs at 100%: Goa, Haryana, Gujarat, Punjab, Himachal Pradesh, Telangana, Mizoram, Arunachal Pradesh, Puducherry, Andaman & Nicobar Islands, Dadra & Nagar Haveli/Daman & Diu
JJM 2.0 — Cabinet Approval (March 2026):
- Cabinet approval: March 2026 (Union Cabinet)
- Extended deadline: December 2028 (from original March 2024)
- Enhanced budget: ₹8.69 lakh crore total (central assistance: ₹3.59 lakh crore — an increase of ₹1.51 lakh crore from the original 2019 allocation of ₹3.60 lakh crore)
- Ministry: Ministry of Jal Shakti (MoJS)
Structural shifts in JJM 2.0 (from 1.0):
| Feature | JJM 1.0 (2019-2024) | JJM 2.0 (2025-2028) |
|---|---|---|
| Primary metric | Number of connections created | Functional, sustainable service delivery |
| Focus | Infrastructure creation (pipes, tanks) | Governance, O&M, quality |
| Water quality | Secondary | Primary — FTK testing mandatory |
| Urban water | Separate AMRUT scheme | Greater convergence |
| Har Ghar Jal certification | Emerging | Core deliverable — all GPs to be certified |
Har Ghar Jal Certification scale:
- 2.12 lakh villages declared "Har Ghar Jal certified" by early 2026 (out of ~6.4 lakh total rural villages)
- Certification process: Local Gram Sabha resolution → verification by district officials → state certification
- JJM 2.0 target: All 2.5 lakh+ gram panchayats certified by December 2028
Water quality monitoring (JJM data):
- 2,162 laboratories established nationwide for water quality testing
- 66.32 lakh water samples tested (cumulative)
- 24.80 lakh women trained to conduct water quality tests using Field Testing Kits (FTKs) — decentralised quality surveillance replacing laboratory-only testing
UPSC synthesis: JJM is GS2 governance + GS3 water security. The 79.74% coverage figure (February 2025) is the current accurate number — NOT the 78% in the chapter or the original 100% claim for 2024. Key exam facts: JJM launched August 15, 2019 (Independence Day, PM Modi announcement); 19.36 crore rural households; 15.44 crore connected (Feb 2025); 11 states at 100%; ~4 crore gap; Cabinet extended to December 2028 as JJM 2.0 (March 2026); ₹8.69 lakh crore total enhanced budget; 2.12 lakh Har Ghar Jal certified villages; 24.80 lakh women FTK trained. Ministry = Ministry of Jal Shakti (not Ministry of Water Resources — it was merged and renamed in 2019).
[Additional] 8b. Himalayan Glacier Melt — ISRO Data on Retreating Glaciers and GLOF Risk
The chapter discusses water stored in glaciers (68.7% of global freshwater) and the water cycle, but never addresses the accelerating loss of India's Himalayan glacier water reserves — a direct threat to the freshwater supply of over 500 million people dependent on glacier-fed rivers (Indus, Ganga, Brahmaputra). ISRO's 2024 satellite study provides verified Indian data: 75% of Himalayan glaciers are retreating.
Glacier Science — Key Terms:
| Term | Meaning |
|---|---|
| Glacier retreat | When a glacier's terminus (end/snout) moves uphill (backwards) because ice loss > ice accumulation — the glacier shrinks |
| Equilibrium Line Altitude (ELA) | The elevation where annual snowfall equals annual melting — above ELA, glacier grows; below ELA, glacier melts |
| Melt water | Water produced when glaciers melt — feeds rivers during summer; critically important for river flow during dry months |
| Glacial Lake | Lake formed in a valley left behind by a retreating glacier, often dammed by unstable moraine (rocky debris) |
| GLOF (Glacial Lake Outburst Flood) | When a glacial lake dam fails — releases catastrophic volume of water and debris downstream; can destroy villages and dams with little warning |
| Moraine | Accumulated rocky debris pushed by a glacier; when a glacier retreats, moraine dams form weak, unstable barriers holding glacial lakes |
Indian rivers and their glacier dependence:
- Ganga basin: 46,000+ glaciers; glacier meltwater = ~40–60% of dry-season Ganga flow
- Indus basin: Most glacier-dependent; Pakistan's agriculture and Pakistan's freshwater supply critically at risk
- Brahmaputra basin: Fastest-retreating glaciers (20.2 m/year); China-India-Bangladesh shared river
[Additional] Himalayan Glacier Melt and GLOF Risk (GS1 — Physical Geography / GS3 — Disaster Management):
ISRO SAC Glacier Retreat Data (National Remote Sensing Centre):
| Basin | Mean Retreat Rate | Notable Glaciers |
|---|---|---|
| Indus basin | 12.7 m/year | Siachen, Gangotri, Zanskar glaciers |
| Ganga basin | 15.5 m/year | Dokriani (15–20 m/yr), Chorabari (9–11 m/yr) |
| Brahmaputra basin | 20.2 m/year — fastest retreating | Milam, Gangotri, NE Himalayan glaciers |
| Overall HKH (Hindu Kush Himalayan) | 14.9 ± 15.1 m/year average | ~46,000 glaciers across HKH |
- ~75% of Himalayan glaciers are retreating — source: PIB citing ISRO/NCSC data
- Total glacier area in Indian Himalaya: ~37,000 km² (NRSC assessment)
ISRO 2024 Glacial Lake Expansion Study (1984–2023):
- 2,431 glacial lakes identified in Indian Himalayas larger than 10 hectares (2016-17 baseline)
- 676 lakes (27.8%) have notably expanded since 1984
- 601 of those 676 lakes (89%) have more than doubled in size over the 39-year period
- 130 expanding lakes are within India: 65 in Indus basin (Ladakh, J&K), 7 in Ganga basin (Uttarakhand, HP), 58 in Brahmaputra basin (Arunachal Pradesh, Sikkim)
- Ghepang Ghat glacial lake (Himachal Pradesh): 178% size increase from 1989–2022; growing at ~1.96 hectares/year — one of fastest-expanding lakes in India
GLOF events — why the risk is growing:
- As glaciers retreat, moraine-dammed lakes grow larger but dams remain fragile (unstable ice/rock)
- Sikkim GLOF — October 3-4, 2023: South Lhonak Lake (North Sikkim) outburst; 40+ deaths; complete destruction of Teesta-III hydroelectric dam (1,200 MW project, Rs. 8,000+ crore); 4 km of National Highway-10 destroyed; 3,000+ people displaced
- 314 of the expanding lakes are at 4,000–5,000 m elevation; 296 are above 5,000 m — high altitude = more remote, less monitoring, greater cascading impact when GLOF reaches lower valleys
- NDMA has identified GLOFs as a major disaster risk requiring dedicated early warning systems
Policy and monitoring response:
- National Action Plan for Glacial Lake Outburst Floods (NDMA): Risk maps for all major glacial lake districts
- NISAR mission (NASA-ISRO Synthetic Aperture Radar, launched 30 July 2025 by GSLV-F16 from Sriharikota): uses dual-frequency L-band + S-band SAR to measure glacier movement and ice-sheet changes globally at 12-day intervals — dramatically improves real-time glacier monitoring; commissioning underway since launch
- High Altitude Hydrology Project (NDMA + NRSC): Drone-based monitoring of high-risk glacial lakes in Sikkim, Uttarakhand, Himachal Pradesh
- Namami Gange indirect link: Ganga basin glacier health directly determines Ganga's long-term water availability — the Rs.42,019 crore Namami Gange restoration programme's success depends on adequate glacier-sourced base flow
UPSC synthesis: Himalayan glacier melt is GS1 (physical geography — cryosphere) + GS3 (disaster management — GLOF, environment) combined. ISRO data is the authoritative Indian source. Key exam facts: 14.9 m/year mean Himalayan glacier retreat; Brahmaputra basin fastest (20.2 m/yr); 75% glaciers retreating; 676 lakes expanded (1984-2023), 601 doubled in size; 130 expanding lakes in India; Ghepang Ghat HP = 178% expansion; Sikkim GLOF October 2023 (South Lhonak Lake, Teesta-III dam destroyed); ISRO NISAR launched 2024 (NASA-ISRO SAR for ice monitoring); NDMA GLOF risk maps published. Always distinguish: glacier retreat ≠ GLOF; retreat is slow/gradual; GLOF is sudden catastrophic flood.
Exam Strategy
Prelims traps:
- Water is densest at 4°C, not 0°C — a classic trap.
- Ice floats because it is less dense (0.92 g/cm³) than liquid water (~1.0 g/cm³).
- Evaporation happens at any temperature, not just at 100°C; boiling is specifically at 100°C (sea level).
- Water vapour is invisible — "steam" you see in the kitchen is condensed droplets, not pure vapour.
- Sublimation = solid to gas directly (bypassing liquid phase); freeze-drying and dry ice are examples.
- Utilisable water in India is ~1,123 BCM, not 4,000 BCM (total precipitation).
- India is water-stressed (< 1,700 m³/person/year) but not yet water-scarce (< 1,000 m³/person/year) nationally — though some regions are scarce.
Mains angles:
- Himalayan glacier retreat and India's freshwater security.
- Groundwater depletion — causes, consequences, policy responses (Atal Bhujal Yojana).
- River interlinking — Ken-Betwa project: benefits vs. ecological and displacement concerns.
- Jal Jeevan Mission — coverage, funding, challenges in last-mile delivery.
Practice Questions
Prelims:
With reference to water resources in India, which of the following statements is correct?
(a) India's per capita water availability exceeds the water scarcity threshold
(b) India extracts the largest volume of groundwater in the world
(c) The Namami Gange programme focuses only on Uttarakhand
(d) India treats more than 70% of its wastewaterThe phenomenon of anomalous expansion of water is best described as:
(a) Water contracts continuously as it cools from 100°C to 0°C
(b) Water expands when cooled below 4°C, causing ice to be less dense than liquid water
(c) Water reaches maximum density at 0°C
(d) Ice sinks in water due to its higher densityWhich of the following connects the Ken River (Madhya Pradesh) to the Betwa River (Uttar Pradesh)?
(a) Polavaram Project
(b) Kaleshwaram Project
(c) Ken-Betwa River Interlinking Project
(d) Godavari-Krishna Interlinking Project
Mains:
"Himalayan glaciers are the water towers of Asia." Examine the threat posed by their accelerated melting to water security in South Asia and suggest measures to address this challenge. (CSE Mains 2022, GS Paper 3, 15 marks)
Critically examine the Ken-Betwa river interlinking project from ecological, social, and developmental perspectives. (CSE Mains 2023, GS Paper 3, 15 marks)
