Water

UPSC GS1 — Ocean Currents:

What causes ocean currents?

1. Wind: Surface winds drag water; Trade winds drive equatorial currents westward
2. Temperature differences: Warm water is less dense and floats; cold water sinks (thermohaline circulation)
3. Salinity differences: Saltier water is denser; sinks relative to less salty water
4. Earth's rotation (Coriolis effect): Deflects currents to the right (NH) or left (SH) → creates circular gyres

Gyres: Large circular current systems in each ocean:

• Subtropical gyres (warm in tropics, cold on eastern sides): North Atlantic, South Atlantic, North Pacific, South Pacific, Indian Ocean
• The western side of gyres = warm currents (Gulf Stream = western boundary of North Atlantic Gyre)
• The eastern side = cold currents (Canary Current, Humboldt — eastern North and South Atlantic/Pacific)

Why cold currents create deserts: Cold currents chill the air above them → air cannot hold much moisture → any moist air coming off the ocean is already dried out. When onshore winds blow, they bring little rain. Result: coastal deserts even in otherwise humid latitudes.

• Atacama Desert (South America): Humboldt cold current
• Namib Desert (Africa): Benguela cold current
• Western Sahara coast: Canary cold current

Thermohaline circulation ("Ocean Conveyor Belt"): Global slow-moving deep ocean circulation driven by temperature (thermo) and salinity (haline) differences. Carries heat from tropics to polar regions; regulates global climate. Climate change concern: melting Arctic ice adds freshwater → reduces salinity → may slow or disrupt the conveyor → could cause rapid cooling of Europe despite global warming (called AMOC — Atlantic Meridional Overturning Circulation).

[Additional] India's Groundwater Crisis and Policy Response (GS2 — Governance / GS3 — Water Resources):

India's groundwater — key facts (CGWB 2024 Report):

States with worst depletion (extraction as % of annual recharge):

Punjab + Haryana together lost approximately 64.6 BCM of groundwater over 17 years — driven by subsidized/free electricity to agricultural pumps, which eliminates the economic deterrent to over-extraction.

National Water Policy 2012 — key principles:

• Water = national resource (public trust doctrine — not a commodity to be privately owned)
• River basin as the unit of planning and management
• Priority order: (1) Drinking water + sanitation = pre-emptive need (non-negotiable, not just "first priority"); (2) Food security/livelihoods of the poor; (3) Minimum ecological/environmental flows; (4) After the above — water is treated as an economic good and priced accordingly
• NWP 2012 explicitly moved away from rigid ranked priority lists of 1987 and 2002 policies — "pre-emptive need" is a stronger formulation than "first priority"

Jal Jeevan Mission (Har Ghar Jal):

Atal Bhujal Yojana:

PM KUSUM — solar pumps and groundwater paradox:

• PM KUSUM (Pradhan Mantri Kisan Urja Suraksha Evam Utthan Mahabhiyan) installs solar pumps for farmers — eliminates diesel cost but also eliminates economic deterrent to over-pumping
• Studies show solar pumps at zero marginal cost can accelerate groundwater depletion unless combined with metering and volumetric limits — a critical governance gap

AMRUT 2.0 (Urban Water Supply):

• Launched: 1 October 2021; covers ~4,900 statutory towns
• Target: Universal piped water supply; standard = 135 LPCD; reduce non-revenue water losses below 20%
• Total outlay: Rs 2,77,000 crore (central share: Rs 76,760 crore)
• JJM (rural) + AMRUT 2.0 (urban) = together aim for universal tap water coverage across India

UPSC synthesis: India Groundwater = GS3 Water Resources + GS2 Governance. Key exam facts: India = world's largest groundwater extractor = 245.64 BCM/year (2024); 87% to agriculture; stage of extraction = 60.47%; over-exploited = 11.13% of units (736 out of 6,553); Punjab = ~163% stage = worst; Jal Shakti Ministry = 31 May 2019 = merger; NWP 2012 = drinking water = pre-emptive need (NOT just "first priority"); Jal Jeevan Mission = 15 August 2019 = rural = 55 LPCD = 78.58% coverage (Oct 2024) = budget Rs 3.60 lakh crore = deadline extended to 2028; Atal Bhujal Yojana = 25 December 2019 = 7 states = Rs 6,000 crore = 50% World Bank = community-based demand-side management = 8,350 GPs; NAQUIM = CGWB = started 2012; AMRUT 2.0 = 1 October 2021 = urban = ~4,900 towns = 135 LPCD. Prelims trap: JJM = 15 August 2019 (NOT 2020 — many confuse with COVID year); JJM covers rural households (NOT urban — AMRUT 2.0 is for urban); Atal Bhujal Yojana = 7 states (NOT all states); World Bank funds 50% of Atal Bhujal (NOT GoI alone); India's stage of extraction = 60.47% nationally (NOT >100% — Punjab at 163% is a state-level figure, NOT national); NWP 2012 = drinking water = pre-emptive need (NOT merely "first priority" — this is a stronger, more categorical formulation).

[Additional] Himalayan Glaciers, Third Pole, Peak Water, and GLOFs (GS1 — Physical Geography / GS3 — Disaster Management + Environment):

The Third Pole — key statistics (ICIMOD HI-WISE Report):

Key Indian glaciers:

ICIMOD glacier loss projections by 2100 (HKH Assessment):

Critical fact: Himalayan glaciers lost ice 65% faster in 2010–2019 than in 2001–2010. Mountain temperatures rise ~2°C for every 1.5°C of global warming — the Himalayas warm faster than the global average.

River dependence on Himalayan glacier melt:

Peak water timeline:

• Before peak water (~to 2050): Some basins may temporarily receive MORE meltwater as temperatures rise — misleading "more water" phase
• After peak water (post-2050): Glacier mass so reduced that melt contributions decline → chronic water stress for agriculture and hydropower in dry seasons
• Peak water for HKH basins: ~2028 (low emissions) to 2059 (high emissions) depending on scenario
• The Indus basin is already past peak water in some sub-basins

Glacial Lake Outburst Floods (GLOFs):

South Lhonak GLOF, Sikkim — October 2023:

ICIMOD:

• Full name: International Centre for Integrated Mountain Development
• HQ: Lalitpur (Kathmandu Valley), Nepal
• 8 member countries: Afghanistan, Bangladesh, Bhutan, China, India, Myanmar, Nepal, Pakistan

UPSC synthesis: Himalayan Glaciers = GS1 Physical Geography + GS3 Environment + Disaster Management. Key exam facts: Third Pole = HKH = 54,252 glaciers + ~60,054 km² + ~6,127 km³ ice volume; ICIMOD HQ = Lalitpur (Kathmandu Valley), Nepal + 8 member countries (Afghanistan, Bangladesh, Bhutan, China, India, Myanmar, Nepal, Pakistan); Siachen = largest glacier in India = ~76 km = Ladakh = Karakoram = Indian control since 1984; Gangotri feeds Bhagirathi = retreating ~18 m/year (2017–2023); ICIMOD projection = 50% ice loss at 2°C by 2100; Indus = most glacier-dependent = ~40% of upper basin runoff from glacier melt; peak water (HKH) = ~2028–2059 depending on scenario; post-peak = chronic dry-season water stress; 190 very high risk glacial lakes in India; South Lhonak GLOF = 3–4 October 2023 = Sikkim = ~50 million m³ = Teesta III dam destroyed = 77 deaths = climate change confirmed. Prelims trap: Siachen = Karakoram Range (NOT the main Himalayan range — Karakoram is a separate range; Gangotri, Zemu, Bara Shigri are in the main Himalayan/Zanskar ranges); Gangotri feeds Bhagirathi (NOT directly the Ganga — Bhagirathi joins Alaknanda at Devprayag to form the Ganga); Indus = most glacier-dependent (NOT Ganga — Ganga's glacier melt share is only ~13%; Indus is ~40%); peak water = temporarily MORE water then permanent decline (NOT immediately less water — this sequence is critical); ICIMOD = 8 members (India + 7 others including China — China is a member).