GS Paper I 2020 · Q6
10 marks · 150 words Geophysical phenomena & changing features X-Ray · Core #23How will the melting of Himalayan glaciers have a far-reaching impact on the water resources of India?
Approach · directive: “how”
What it asks · Explain how glacier retreat alters river flows, floods, hydropower and water availability in India, in the short run and the long run.
It asks 2 things — answer each
- Explain how glacier melt changes river flows: more water first, less later, and a lost dry-season buffer
- Explain the far-reaching impacts on India's water resources: floods, hydropower, silt, shared rivers, with a way forward
Open with · ISRO satellite data (1984–2023) show 676 of 2,431 large Himalayan glacial lakes have notably expanded since 1984; glaciers are India's frozen reservoirs, so their retreat changes both the volume and timing of river water.
Cover
- Peak water, then decline: faster melt first swells rivers, then lean-season flow falls; Chandra basin glaciers lost about 6% of area in 20 years (NCPOR).
- Lost dry-season buffer: pre-monsoon melt supports drinking water and rabi irrigation in the plains; erratic supply pushes farmers to groundwater.
- Outburst floods: South Lhonak lake in Sikkim drained about 105 ha in October 2023 (ISRO); Chamoli flood of February 2021.
- Hydropower: the Teesta-III dam collapsed in October 2023, so CWC is reviewing design floods of dams exposed to glacial lake bursts.
- Silt, shared rivers and ecosystems: rain replacing snow brings flashier floods and silt; shifting flows strain water sharing, springs and wetlands.
- Way forward: automatic weather stations and early warning at glacial lakes, glacier monitoring under NMSHE, springshed management and efficient irrigation.
Close with · Glaciers are a slowly emptying reservoir: today's surplus melt must be stored and recharged, basin by basin, for leaner decades ahead.
Add value (verified)
- ISRO's long-term satellite study finds 676 of 2,431 large glacial lakes in Indian Himalayan basins have expanded since 1984.ISRO — Satellite Insights: Expanding Glacial Lakes in the Indian Himalayas ↗“Of the 2,431 lakes larger than 10 hectares identified during 2016-17, 676 glacial lakes have notably expanded since 1984.”
- NCPOR's inventory shows Chandra basin glaciers lost about 6% of glacial area in 20 years.PIB — Parliament Question: Adverse effects of climate change on Himalayas (MoES) ↗“The glacier inventory prepared by NCPOR for the Chandra basin shows that it has lost about 6% of its glacial area during last 20 years.”
- South Lhonak lake in Sikkim burst in October 2023, draining about 105 hectares.ISRO — Satellite image-based studies of South Lhonak Lake ↗“It is observed that Lake is Burst and about 105 Hectares area has been drained out (28 September 2023 image versus 04 October 2023) which might have created a flash flood downstream.”
- After the Teesta-III dam collapse, CWC began reviewing design floods of dams vulnerable to GLOFs.PIB — Parliament Question on glacial lake outburst floods (Ministry of Jal Shakti) ↗“Subsequent to Teesta-III Hydroelectric dam collapse in October, 2023, CWC has decided to review the design flood of all the existing and under construction dams”
Question: UPSC's CS (Main) 2020, GS Paper I — paper ↗. Approach: Minimalist IAS, checked 16 Oct 2026 (how we verify) — UPSC publishes no model answers. ·
Model answer· 222words · Minimalist IAS
ISRO's satellite record (1984–2023) shows 676 of 2,431 large glacial lakes have notably expanded, a sign of retreating ice. Glaciers are frozen reservoirs for the Indus, Ganga and Brahmaputra, so their melt changes how much water India gets, and when.
How melting changes river flows
- Peak water, then decline: melt first swells rivers, then flows fall as ice shrinks; NCPOR finds Chandra basin glaciers lost about 6% of their area in 20 years.
- Lost dry-season buffer: pre-monsoon melt feeds drinking water and rabi irrigation in the plains; when it falters, farmers turn to groundwater.
- Warming
- faster melt
- growing glacial lakes
- shrinking ice store
- weak lean-season flow
Far-reaching impacts on water resources
- Outburst floods: South Lhonak lake in Sikkim burst in October 2023, draining about 105 hectares (ISRO); Chamoli flooded in February 2021.
- Hydropower at risk: after the Teesta-III dam collapsed in October 2023, the Central Water Commission began reviewing design floods of vulnerable dams.
- Silt, shared rivers, ecosystems: flashier, silt-laden floods fill reservoirs, strain water sharing and dry out springs.
Way forward
- Warn, monitor, conserve: automatic weather stations and early-warning systems in Sikkim after the 2023 outburst, glacier studies under the National Mission for Sustaining the Himalayan Ecosystem, springshed revival and micro-irrigation.
Glaciers are a slowly emptying reservoir: today's surplus melt must be stored and recharged, basin by basin, for leaner decades.
Prepared by Minimalist IAS to the answer standard of Shivam Singh (mentor, 7 years) · facts checked against official sources (how we verify) · updated 16 Oct 2026. UPSC publishes no model answers: compare your structure and coverage with this, then write your own.
