💥UPSC 2027,2028 Mentorship (April Batch) + Access XFactor Notes & Microthemes PDF
Talk to mentor

Civilsdaily

Login

Type: Prelims Only

  • Gravitational Wave Observations

    Laser Interferometer Lunar Antenna (LILA) Project

    Prelims Only | Science Tech | Mains Paper 3: Awareness in various sc and tech fields

    Why in the News?

    Scientists are planning the Laser Interferometer Lunar Antenna (LILA) Project on the Moon to bypass seismic noise, atmosphere, and frequency limits faced by Earth-based detectors like Laser Interferometer Gravitational-wave Observatory (LIGO).

    What are Gravitational Waves?

    • Overview: Gravitational waves are ripples in the spacetime continuum created when massive objects such as black holes or neutron stars collide.
    • Speed & Effect: They travel at the speed of light, subtly stretching and compressing spacetime. On small scales, effects are extremely weak (e.g., Earth–Moon distance altered by less than an atom’s diameter).
    • Prediction: Proposed by Albert Einstein (1916) in his General Theory of Relativity.
    • First Detection: In 2015, LIGO recorded the first gravitational waves from two colliding black holes 1.3 billion light-years away, confirming their existence.

    Detection on Earth and Challenges:

    • Ground Observatories: LIGO (USA), Virgo (Italy), KAGRA (Japan), GEO600 (Germany) use laser interferometers to detect minuscule delays in light caused by waves.
    • Working of LIGO: Two L-shaped detectors (Louisiana, Washington), each with 4 km arms; differences in reflections signal gravitational waves.
    • Detection Range: Sensitive to events up to 7 billion light years away; frequency range ~100–1,000 Hz.
    • Challenges: Seismic noise, atmosphere, and human activity mask weaker signals.
    • Future Space Missions:
      • LISA (Laser Interferometer Space Antenna, 2030s): Three satellites in triangular formation, sensitive to 0.1 millihertz–0.1 hertz.
      • SKA (Square Kilometre Array, Australia & South Africa): Monitors pulsars for nanohertz waves.
      • Decihertz Gap: Frequencies 0.1–10 Hz remain unexplored, which LILA aims to study.

    About Laser Interferometer Lunar Antenna (LILA) Project

    • Overview: Proposed by Vanderbilt Lunar Labs, USA, to build a gravitational-wave detector on the Moon.
    • Ideal Conditions: The Moon’s polar shadow zones provide ultra-low seismic activity, natural vacuum, and no atmospheric or radio interference.
    • Focus: Sub-hertz gravitational waves, vital for studying intermediate-mass black holes and the early universe.
    • Phases:
      • LILA Pioneer: Can be deployed within this decade using American lunar landers (Blue Origin, Intuitive Machines) and possibly India’s Chandrayaan programme.
      • LILA Horizon: Advanced phase requiring astronauts for setup.
    • Cosmic Symphony Analogy:
      • SKA: Captures low-frequency “bass notes.”
      • LIGO (and future LIGO-India): Detects high-pitched bursts from stellar collisions.
      • LILA: Covers missing middle frequencies, completing the “cosmic raag.”
    • Historical Note: Since Apollo, retro-reflectors on the Moon track Earth–Moon distance. Some scientists suggest the Earth–Moon system itself acts as a natural detector.

    Significance:

    • Scientific Advancement: Opens the decihertz frontier, inaccessible so far.
    • Global Collaboration: Complements LIGO-India (IndIGO project), operational by 2030.
    • Research Potential: Helps study intermediate-mass black holes, cosmic mergers, and universe origins.
    • Lunar Astronomy: Marks the start of using the Moon as a laboratory for space science.
    • Holistic Coverage: With LISA, SKA, and Earth detectors, LILA would map the entire gravitational-wave spectrum, giving a complete picture of the universe.
    [UPSC 2020] The experiment will employ a trio of spacecraft flying in formation in the shape of an equilateral triangle that has sides one million kilometres long, with lasers shining between the craft.”  The experiment in question refers to

    Options: (a) Voyager-2 (b) New Horizons (c) LISA Pathfinder (d) Evolved LISA*

     

    Get an IAS/IPS ranker as your 1: 1 personal mentor

  • Water Management – Institutional Reforms, Conservation Efforts, etc.

    [pib] Siphon-Based Thermal Desalination System

    Prelims Only | Science Tech | Mains Paper 3: S&T – Applications In Everyday Life

    Why in the News?

    Researchers at the Indian Institute of Science (IISc) have developed a siphon-based thermal desalination system that overcomes siltation issues, offering a low-cost and scalable solution.

    About Siphon-Based Thermal Desalination System:

    • Overview: Developed by Indian Institute of Science (IISc) researchers to overcome the inefficiencies of conventional solar stills.
    • Purpose: Designed as a low-cost, scalable, and sustainable freshwater solution for off-grid and water-stressed regions.

    • Working: 

      • Principle: Works on siphonage, where a fabric wick draws salty water and gravity maintains continuous flow.
      • Innovation: A grooved metallic surface flushes away salt deposits before crystallization, preventing clogging.
      • Process: Salty water evaporates as a thin film on a heated surface and condenses just 2 mm away on a cooler surface, ensuring high efficiency.

    Key Features:

    • High Efficiency: Generates >6 liters of freshwater per sq. m per hour under sunlight — several times more than conventional solar stills.
    • Multistage Design: Uses stacked evaporator–condenser pairs to recycle heat and boost output.
    • Salt Resistance: Handles up to 20% salinity without clogging, making it effective even for brine treatment.
    • Affordable Materials: Built from aluminum and fabric, keeping costs low.
    • Energy Flexibility: Operates on solar power or waste heat, adaptable to different settings.
    • Scalable Applications: Useful for villages, disaster zones, and island communities.
    • Sustainability: Offers a clean, low-maintenance desalination method without reliance on complex machinery.
    [UPSC 2008] Where was the first desalination plant in India to produce one lakh liters of freshwater per day based on low-temperature thermal desalination principle commissioned?

    Options: (a) Kavaratti * (b) Port Blair (c) Mangalore (d) Valsad

     

    Get an IAS/IPS ranker as your 1: 1 personal mentor

  • Foreign Policy Watch: India-SAARC Nations

    Kokrajhar-Gelephu and Banarhat-Samtse Railway Lines to Bhutan

    Prelims Only | International Relations | Mains Paper 2: India & Its Neighborhood – Relations

    Why in the News?

    India and Bhutan have launched their first-ever rail links, connecting Kokrajhar–Gelephu (69 km, Assam–Bhutan) and Banarhat–Samtse (20 km, West Bengal–Bhutan).

    Kokrajhar-Gelephu and Banarhat-Samtse Railway Lines to Bhutan

    About India–Bhutan Railway Connectivity:

    • Overview: Agreements were signed during PM Modi’s visit to Bhutan (March 2024) and formalised in 2025.
    • Projects:
      1. Kokrajhar–Gelephu line: 6 stations, multiple bridges, viaducts, designed for Vande Bharat trains; expected completion in 4 years.
      2. Banarhat–Samtse line: 2 stations, major & minor bridges, flyovers, underpasses; expected completion in 3 years.
    • Both lines will be fully electrified, giving Bhutan direct access to India’s 1,50,000 km railway network, boosting passenger and goods transport.

    Significance of the Project for India:

    • Bilateral Relations: Strengthens ties with Bhutan, India’s closest neighbour and largest recipient of Indian development assistance.
    • Strategic Security: Enhances regional security and serves as a counterbalance to China’s influence in South Asia.
    • Economic Integration: Supports Bhutan’s trade (80% with India), boosts hydropower exports, and aids industrial development.
    • Tourism & Culture: Improves people-to-people exchanges, especially linking Gelephu’s Mindfulness City and Samtse’s industrial hub.
    • Act East Policy: Advances India’s policy through cross-border infrastructure in the eastern and northeastern region.
    • Rail Diplomacy: Positions Indian Railways as a strategic enabler of diplomacy and connectivity in the neighbourhood.
    [UPSC 2023] With reference to India’s projects on connectivity, consider the following statements:

    1. East-West Corridor under Golden Quadrilateral Project connects Dibrugarh and Surat.

    2. Trilateral Highway connects Moreh in Manipur and Chiang Mai in Thailand via Myanmar.

    3. Bangladesh-China-India-Myanmar Economic Corridor connects Varanasi in Uttar Pradesh with Kunming in China.

    How many of the above statements are correct?

    Options: (a) Only one (b) Only two (c) All three (d) None*

     

    Get an IAS/IPS ranker as your 1: 1 personal mentor

  • Wetland Conservation

    Bihar adds 2 more Wetlands to Ramsar List

    National Parks/WSPrelims Only | Enviro & Biodiversity | Mains Paper 3: Conservation, Environmental Pollution & Degradation, Eia

    Why in the News?

    India has added two new wetlands in Bihar, Gokul Jalashay (Buxar district) and Udaipur Jheel (West Champaran district), to the global Ramsar list of Wetlands of International Importance.

    Important Facts:

    • With this, India’s Ramsar sites rise to 93, consolidating its top rank in Asia and third in the world, after the UK (176) and Mexico (144).
      • Bolivia has the largest Ramsar wetland area (Llanos de Moxos wetlands – 6.9 million ha).
    • India’s Ramsar sites have expanded from 26 in 2012 to 93 in 2025, covering 13.6 lakh hectares, with 51 sites added since 2020.
    • Globally, there are 2,544 Ramsar sites.

    Facts about the two Wetlands:

    1. Gokul Jalashay (Buxar District):

      • Oxbow lake spread over 448 hectares on the southern edge of the Ganga River.
      • Acts as a flood buffer during high water events.
      • Supports 50+ bird species and provides livelihoods through fishing, farming, and irrigation.

    2. Udaipur Jheel (West Champaran District):

      • Oxbow lake covering 319 hectares, part of the Udaipur Wildlife Sanctuary ecosystem, formed by the Gandaki River.
      • Enhances ecological connectivity and supports the Central Asian Flyway for migratory birds.

    About the Ramsar Convention:

    • Establishment: Signed on 2 February 1971 in Ramsar, Iran.
    • Objective: Provide a framework for conservation and wise use of wetlands and their resources.
    • Functions:
      • Identify and designate wetlands of international importance.
      • Promote effective management of wetlands.
      • Foster international cooperation for conservation.
    • Members: 173 countries (as of 2025).
    • India and Ramsar:
      • India joined in 1982.
      • First Ramsar site: Chilika Lake, Odisha (1981).
      • Current total: 93 sites (Sept 2025), covering 13,60,718 hectares.
      • Growth: From 26 sites in 2012 to 93 in 2025 (51 added since 2020).
      • State-wise: Tamil Nadu has the highest (20), followed by Uttar Pradesh (10).
      • About 10% of India’s total wetland area is under Ramsar listing.
    • Montreux Record: List of Ramsar sites under threat of ecological change.
      • 48 sites globally (2025).
      • 2 Indian sites included: Keoladeo National Park (Rajasthan) and Loktak Lake (Manipur).
    • World Wetlands Day: Celebrated on February 2nd every year.
      • 2025 Theme: “Protecting Wetlands for Our Common Future”.

    Criteria for Declaration (9 Criteria):

    A wetland can be declared a Ramsar site if it meets at least one of these:

    1. Has unique, rare, or representative wetland types.
    2. Supports vulnerable, endangered, or endemic species.
    3. Provides critical habitat for waterfowl, especially during migration.
    4. Contains significant ecological, botanical, zoological, limnological, or hydrological features.
    5. Supports biodiversity conservation and scientific research.
    6. Provides ecosystem services like flood control, groundwater recharge, and water purification.
    7. Has cultural, spiritual, or recreational importance.
    8. Ensures sustainable livelihoods for local communities.
    9. Faces threats requiring international cooperation for conservation.
    [UPSC 2022] Consider the following pairs:

    Wetland/Lake Location

    1. Hokera Wetland — Punjab 2. Renuka Wetland — Himachal Pradesh

    3. Rudrasagar Lake — Tripura 4. Sasthamkotta Lake — Tamil Nadu

    How many pairs given above are correctly matched?

    Options: (a) Only one pair (b) Only two pairs* (c) Only three pairs (d) All four pairs

     

    Get an IAS/IPS ranker as your 1: 1 personal mentor

  • World’s highest bridge opens to traffic in China 

    Prelims Only | Economics | Mains Paper 3: Infrastructure: Energy, Ports, Roads, Airports, Railways Etc.

    Why in the News?

    The Huajiang Grand Canyon Bridge in Guizhou province, China, is now the world’s tallest bridge, standing 625 m above the Beipan River.

    World's highest bridge opens to traffic in China 

    About Huajiang Grand Canyon Bridge:

    • Height: Rises 625 m above the Beipan River, surpassing the previous record-holder, the Beipanjiang Bridge (565 m).
    • Connectivity: Links the Liuzhi Special District and Anlong Special District, reducing travel time from 2 hours to just 2 minutes.
    • Transport Network: Part of the Guizhou S57 Expressway and the 190 km Shantian–Puxi Expressway, boosting transport, economy, and tourism.
    • Engineering Hub: Guizhou, called the “bridge museum of the world”, now has nearly half of the world’s 100 tallest bridges, showcasing China’s leadership in high-altitude civil engineering.

    Key Features of the Bridge:

    • Height Record: Deck-to-water clearance of 625 m, taller than most skyscrapers.
    • Span & Length: Total length 2,890 m, with a 1,420 m suspension span, the longest in any mountainous region globally.
    • Construction: Began January 2022, completed in just over three years; final truss installed January 2025; load-tested with 96 trucks.

    Get an IAS/IPS ranker as your 1: 1 personal mentor

  • Forest Conservation Efforts – NFP, Western Ghats, etc.

    Cold Desert named India’s 13th UNESCO Biosphere Reserve

    National Parks/WSPrelims Only | Enviro & Biodiversity | Mains Paper 3: Conservation, Environmental Pollution & Degradation, Eia

    Why in the News?

    UNESCO added India’s Cold Desert Biosphere Reserve (CDBR) to the World Network of Biosphere Reserves (WNBR) under the Man and the Biosphere (MAB) programme.

    With this, India now has 13 UNESCO-recognized biosphere reserves out of 18 designated nationally.

    What are UNESCO Biosphere Reserves?

    • Overview: Sites integrating biodiversity conservation + cultural heritage + sustainable development.
    • Programme: MAB (1971).
    • Designation Criteria:
      • Must include a protected core zone.
      • Must represent a unique biogeographical unit.
      • Involve local communities in conservation.
      • Potential to preserve traditional lifestyles.
    • Functions: Conservation, Development, Logistic Support.
    • Global Network (WNBR): 785 sites, 142 countries (2025); 7.4 million sq. km (~5% Earth’s surface); home to 275 million people.

    About Cold Desert Biosphere Reserve (CDBR):

    • Location: Lahaul–Spiti (Himachal Pradesh), part of Trans-Himalayan biogeographic province.
    • Constituents: Includes Pin Valley National Park, Kibber Wildlife Sanctuary, Chandratal Wetland, Sarchu Plains.
    • Biodiversity:
      • Flora:  732 vascular plants, incl. 30 endemic, 47 medicinal plants (Amchi / Sowa Rigpa).
      • Fauna: Snow leopard (flagship), Tibetan wolf, Himalayan ibex, blue sheep (800+ in Spiti), Himalayan snowcock, golden eagle, bearded vulture.
    • Communities: ~12,000 people; practice yak & goat herding, barley/pea farming, Tibetan herbal medicine, Buddhist monastic councils.
    • Significance: Boosts eco-tourism, climate research, community-led conservation, sustainable livelihoods. Supports climate-resilient development in fragile ecosystems.

    cold desert biosphere reserve

    Biosphere Reserves in India:

    • Total: 18 designated, of which 13 in UNESCO-WNBR (as of 2025).
    • First: Nilgiri BR (1986); Largest: Gulf of Kachchh (Gujarat); Smallest: Dibru-Saikhowa (Assam).
    • Scheme: Launched 1986; implemented by MoEFCC under MAB Programme.
    • Three zones: Each biosphere reserve is organised into-
      1. Core zone (strictly protected),
      2. Buffer zone (limited human activity such as research, grazing, and tourism permitted), and
      3. Transition zone (sustainable human settlements and economic activities allowed).
    • Funding: 90:10 (NE & Himalayan states); 60:40 (others).
    [UPSC 2019] Which of the following are in Agasthyamala Biosphere Reserve?

    Options: (a) Neyyar, Peppara and Shendurney Wildlife Sanctuaries; and Kalakad Mundanthurai Tiger Reserve*

    (b) Mudumalai, Sathyamangalam and Wayanad Wildlife Sanctuaries; and Silent Valley National Park

    (c) Kaundinya, Gundla Brahmeswaram and Papikonda Wildlife Sanctuaries; and Mukurthi National Park

    (d) Kawal and Sri Venkateswara Wildlife Sanctuaries; and Nagarjunasagar-Srisailam Tiger Reserve

     

    Get an IAS/IPS ranker as your 1: 1 personal mentor

  • Internal Security Architecture Shortcomings – Key Forces, NIA, IB, CCTNS, etc.

    National Security Act of 1980

    Prelims Only | Security Issues | Mains Paper 3: External State & Non-State Actors: Challenges To Internal Security.

    Why in the News?

    Climate activist Sonam Wangchuk, leading the demand for statehood and Sixth Schedule protections for Ladakh, was detained under the National Security Act (NSA) in Leh.

    About the National Security Act, 1980:

    • Enactment: Passed on 23 September 1980; applicable across India (earlier not in Jammu & Kashmir).
    • Constitutional Basis: Rooted in Article 22(3)(b) (preventive detention permitted) and Article 22(4) (limit of 3 months unless Board approves).
    • Objective: Provides for preventive detention to safeguard defence, national security, public order, foreign relations, and essential supplies/services.
    • Grounds for Detention: Acts prejudicial to India’s defence or security, harming foreign relations, disturbing public order, endangering essential supplies, or regulating foreigners’ presence/expulsion.
    • Authorities Empowered: Centre, States, District Magistrates, and Police Commissioners (if authorised).
    • Duration: Detention up to 12 months; must communicate grounds within 5 days (extendable to 15). A person can be held 10 days without disclosure of charges.
    • Advisory Board: Composed of three persons qualified to be High Court judges. Orders reviewed within 3 weeks; if no sufficient cause exists, release is mandatory.
    • Background: Builds on colonial-era Bengal Regulation III (1818), Rowlatt Acts (1919), post-independence Preventive Detention Act (1950), and MISA (1971, repealed 1977). Reintroduced by Indira Gandhi in 1980.

    Legal Options after Arrest under NSA:

    • Representation to Government: Detainee can file a written representation challenging detention.
    • Advisory Board Review: Must be reviewed within 3 weeks; release ordered if detention unjustified.
    • Judicial Remedies: Writ petition in High Court (Art. 226) or Supreme Court (Art. 32).
    • Revocation: Centre or State may revoke detention anytime.
    • Limitations: No right to lawyer before Advisory Board; grounds may be withheld in “public interest.”
    [UPSC 2023] Consider the following statements:

    1. According to the Constitution of India, the Central Government has a duty to protect States from internal disturbances.

    2. The Constitution of India exempts the States from providing legal counsel to a person being held for preventive detention.

    3. According to the Prevention of Terrorism Act, 2002, the confession of the accused before the police cannot be used as evidence.

    How many of the above statements are correct?

    (a) Only one* (b) Only two (c) All three (d) None

     

    Get an IAS/IPS ranker as your 1: 1 personal mentor

  • ISRO Missions and Discoveries

    India’s first space observatory AstroSat completes 10 years

    Prelims Only | Science Tech | Mains Paper 3: Achievements Of Indians In S&T

    Why in the News?

    AstroSat, India’s first multi-wavelength space observatory has completed 10 years on September 28, 2025, boosting India’s role in multi-messenger astronomy.

    What is Multi-Messenger Astronomy?

    • Overview:  A modern approach that uses different cosmic messengers to study the universe, not just light.
    • Messengers:
      • Light (photons): Radio, visible, UV, X-ray, gamma rays.
      • Gravitational waves: From black hole/neutron star mergers.
      • Neutrinos: From nuclear reactions in stars.
      • Cosmic rays: Charged particles from space.
    • Insights: Light shows stellar surfaces; Gravitational waves show collisions; Neutrinos probe stellar interiors.
    • Example: 2017 neutron star collision observed with both light and gravitational waves, proving origin of heavy elements like gold.
    • AstroSat’s Role: Enabled simultaneous UV, optical, and X-ray observations, tracking flares, black holes, and neutron stars.

    What is AstroSat?

    • Overview: India’s first dedicated multi-wavelength space observatory, launched on September 28, 2015 by PSLV-C30 from Sriharikota.
    • Objective: To study celestial sources simultaneously in X-ray, ultraviolet (UV), and optical bands, unlike most single-band missions.
    • Management: Controlled by the Mission Operations Complex (MOX), ISTRAC, Bengaluru.
    • Mission Life: Designed for 5 years but operational even after 10 years.
    • Payloads:
      • UVIT (Ultra Violet Imaging Telescope).
      • LAXPC (Large Area X-ray Proportional Counter).
      • CZTI (Cadmium-Zinc-Telluride Imager).
      • SXT (Soft X-ray Telescope).
      • SSM (Scanning Sky Monitor).

    Its Accomplishments:

    • Extended Life: Surpassed design life; still generating data.
    • Black Hole Studies: Captured 500+ black hole births, advancing high-energy astrophysics.
    • Galaxy Detection: Tracked extreme UV light from a galaxy 9.3 billion light-years away, aiding early universe studies.
    • Gamma-Ray Bursts: 500+ bursts studied by CZTI.
    • Discoveries: Identified rare UV-bright Milky Way stars, thousands of times brighter than the Sun.
    [UPSC 2016] With reference to ‘Astrosat’,’ the astronomical observatory launched by India, which of the following statements is/are correct?

    1. Other than USA and Russia, India is the only country to have launched a similar observatory into space.

    2. Astrosat is a 2000 kg satellite placed in an orbit at 1650 km above the surface of the Earth.

    Select the correct answer using the code given below.

    (a) 1 only (b) 2 only (c) Both 1 and 2 (d) Neither 1 nor 2*

     

    Get an IAS/IPS ranker as your 1: 1 personal mentor

  • Modern Indian History-Events and Personalities

    [pib] Who was Rani Rashmoni (1793-1861)?

    Prelims Only | History | Mains Paper 1: Modern Indian History

    Why in the News?

    The Prime Minister has paid tribute to Rani Rashmoni on her birth anniversary on 28th September.

    Rani Rashmoni (1793-1861)

    Who was Rani Rashmoni (1793–1861)?

    • Overview: A prominent zamindar, businesswoman, philanthropist, and social reformer from 19th-century Bengal.
    • Birth: Born on 28 September 1793 in Halisahar, Bengal.
    • Marriage: Married at the age of 11 to Raja Raj Chandra Das, wealthy zamindar of Janbazar, Kolkata.
    • Leadership: Took charge of the estate and business after her husband’s death in 1836, unusual for women of her time.
    • Reputation: Revered as “Lokmata” (Mother of the People) for her courage, administration, and social commitment.

    Her Contributions:

    • Patronage: Built the Dakshineswar Kali Temple (1847–1855); appointed Sri Ramakrishna Paramahamsa as chief priest despite caste opposition.
    • Social Reforms: Opposed polygamy and child marriage; supported widow remarriage; submitted a draft bill against polygamy to the British.
    • Public Welfare & Infrastructure: Constructed major ghats on the Ganga including Babughat, Ahiritola Ghat, Nimtala Ghat. Funded roads, reservoirs, and pilgrim facilities, such as the road from Subarnarekha River to Puri.
    • Resistance to British Rule: Fought against fishing taxes on Hooghly fishermen by blocking river traffic, compelling British to abolish the tax. Defied British restrictions on Durga Puja processions, preserving traditions.
    • Support for Education & Culture: Donated to the Imperial Library (now National Library of India) and Hindu College (now Presidency University). Established schools for women and marginalized groups.
    [UPSC 2024] Consider the following statements about Raja Ram Mohan Roy:

    I. He possessed great love and respect for the traditional philosophical systems of the East.

    II. He desired his countrymen to accept the rational and scientific approach and the principle of human dignity and social equality of all men and women.

    Which of the statements given above is/are correct?

    (a) I only (b) II only (c) Both I and II* (d) Neither I nor II

     

    Get an IAS/IPS ranker as your 1: 1 personal mentor

  • Climate Change Impact on India and World – International Reports, Key Observations, etc.

    Ganga River is drying faster than in 1,300 years: Report

    Prelims Only | Enviro & Biodiversity | Mains Paper 1: Geographical Features & Their Location

    Why in the News?

    A recent study by researchers from IIT Gandhinagar and the University of Arizona warns that the Ganga River is drying at a rate unseen in more than a millennium.

    About Drying of the Ganga River: New Study Findings

    • Overview: Reconstructed streamflow since 700 AD using tree-ring records (Monsoon Asia Drought Atlas) and hydrological models. Validated against historic droughts and famines such as the Bengal famine.

    • Findings:

      • Between 1991 and 2020, multiple droughts lasted 4–7 years, the rarest in the past 1,300 years.
      • The 2004–2010 drought was the most severe in 1,300 years.
      • Post-1990s drying was 76% more intense than the worst 16th-century drought.

    • Causes:

      • Weaker monsoons from Indian Ocean warming and aerosol pollution.
      • Groundwater over-extraction reducing river baseflow.
      • Land-use change disrupting natural recharge.
    • Climate Models: Most fail to reproduce the drying trend, raising doubts about optimistic rainfall projections.
    • Implications: Severe threats to agriculture, 600 million livelihoods, Bay of Bengal ecosystems, and the 40% GDP share of the basin. Calls for adaptive water management.

    ganga

    About the Ganga River:

    • Length: ~2,525 km, the longest river in India.
    • Origin: Gangotri Glacier in Uttarakhand at 3,892 m elevation as Bhagirathi.
    • Formation: Named Ganga at Devprayag after meeting Bhagirathi and Alaknanda.
    • Course: Flows through Uttarakhand, Uttar Pradesh, Bihar, Jharkhand, West Bengal before entering Bangladesh as Padma and emptying into the Bay of Bengal through the Sundarbans Delta.
    • Basin: Covers about 8.61 lakh sq. km, which is 26.4% of India’s area.

    • Tributaries:

      • Left bank: Ramganga, Gomti, Ghaghara, Gandak, Burhi Gandak, Koshi, Mahananda.
      • Right bank: Yamuna, Tons, Karamnasa, Sone, Punpun, Falgu, Kiul, Chandan, Ajoy, Damodar, Rupnarayan.
    • Population: Supports over 600 million people, making it the world’s most densely populated river basin.
    • Cultural Importance: Sacred in Indian culture; declared National River in 2008.
    • Economic Role: Central to agriculture, fisheries, and trade, contributing about 40% of India’s GDP.
    • Ecological Significance: Home to snow leopard, elephants, and Ganga dolphin; includes Corbett, Dudhwa, and Sundarbans reserves.
    • Conservation Efforts: Ganga Action Plan (1985) and Namami Gange Programme (2014); persistent issues of pollution, over-extraction, and climate change.
    [UPSC 2024] With reference to the Himalayan rivers joining the Ganga downstream of Prayagraj from West to East, which one of the following sequences is correct?

    Options: (a) Ghaghara – Gomati – Gandak – Kosi

    (b) Gomati – Ghaghara – Gandak – Kosi*

    (c) Ghaghara – Gomati – Kosi – Gandak

    (d) Gomati – Ghaghara – Kosi – Gandak

     

    Get an IAS/IPS ranker as your 1: 1 personal mentor