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Q13 (IAS/2018) Environment & Ecology › Pollution & Conservation › Water pollution indicators Official Key

Which of the following has/have shrunk immensely/dried up in the recent past due to human activities ? 1. Aral Sea 2. Black Sea 3. Lake Baikal Select the correct answer using the code given below :

Result
Your answer: —  ·  Correct: A
Explanation

The correct answer is option A (1 only).

The Aral Sea experienced a dramatic sea level drop around 1961 due to increasing human impact[1], and has practically ceased to exist as a single water body since then[1]. Water diversions for agricultural purposes from the Amu Darya and Syr Darya rivers beginning in the middle of the last century caused inflows into the Aral Sea to fall by as much as 85 percent by the 1980s[2]. The sea has shrunk by 70% in recent decades due to widespread diversion of rivers and poor water management[3].

Regarding the Black Sea, the provided documents only mention eutrophication issues and temperature variations, but contain no evidence of the sea shrinking immensely or drying up.

For Lake Baikal, while pollution from untreated industrial discharge has led to significant deterioration in water quality and poses a threat to ecological viability[5], there is no evidence in the sources that the lake has shrunk immensely or dried up. Therefore, only the Aral Sea meets the criteria specified in the question.

Sources
  1. [1] http://ndl.ethernet.edu.et/bitstream/123456789/67193/1/2010_Book_TheAralSeaEnvironment.pdf
  2. [2] https://portals.iucn.org/library/efiles/documents/IUCN-EPLP-no.075.pdf
  3. [3] https://www.thegef.org/sites/default/files/publications/SGPIW_Report_CRA-lo_0.pdf
  4. [4] https://documents1.worldbank.org/curated/en/678901468766794877/pdf/multi-page.pdf
  5. [5] https://documents1.worldbank.org/curated/en/678901468766794877/pdf/multi-page.pdf
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Q. Which of the following has/have shrunk immensely/dried up in the recent past due to human activities ? 1. Aral Sea 2. Black Sea 3. Lak…
At a glance
Origin: Mostly Current Affairs Fairness: Low / Borderline fairness Books / CA: 0/10 · 6.7/10
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This is a 'Headline Environmental Event' question. The Aral Sea disaster is the global textbook example of human-induced desiccation. The trap lies in confusing 'polluted' (Black Sea, Baikal) with 'physically disappearing' (Aral). If you read any basic environment module, Aral is page one.

How this question is built

This question can be broken into the following sub-statements. Tap a statement sentence to jump into its detailed analysis.

Statement 1
Has the Aral Sea shrunk immensely or dried up in the recent past due to human activities?
Origin: Web / Current Affairs Fairness: CA heavy Web-answerable

Web source
Presence: 5/5
"natural evolution of the Aral Sea which came to an end around 1961, when increasing human impact resulted in a dramatic sea level drop. Since then, the Aral Sea has practically ceased to exist as a single water body"
Why this source?
  • Explicitly attributes a dramatic sea-level drop to increasing human impact beginning around 1961.
  • States the Aral Sea 'practically ceased to exist as a single water body', supporting the claim of massive shrinkage/drying.
Web source
Presence: 5/5
"riparians on the sister rivers of the Amu Darya and Syr Darya diverted water for agricultural purposes beginning in the middle of the last century. By the 1980’s, inflows from the two rivers into the Aral Sea fell by as much as 85 percent. ... the Aral Sea – a terminal inland lake, which relies on the two rivers for its entire inflow – nearly dried out entirely."
Why this source?
  • Describes large-scale diversion of river water for agriculture under Soviet guidance as the cause.
  • Quantifies inflow reductions (as much as 85%) and concludes the Aral Sea 'nearly dried out entirely.'
Web source
Presence: 5/5
"The Aral Sea, shared by Kazakhstan and Uzbekistan used to be the world’s fourth largest freshwater inland lake. It has since shrunk by 70% in recent decades due to the widespread diversion of rivers, poor water management, and consequential desertification."
Why this source?
  • States the Aral Sea 'used to be the world’s fourth largest freshwater inland lake' and documents a 70% shrinkage.
  • Directly links the shrinkage to human causes: widespread river diversion, poor water management, and desertification.

Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 16: Fluvial Landforms and Cycle of Erosion > 16.3. Drainage Basin or River Basin > p. 208
Strength: 5/5
“• Other terms that are used to describe drainage basins are drainage area, river basin, and water basin. The drainage basin includes both the streams and rivers and the land surface. The drainage basin acts as a funnel by collecting all the water within the area covered by the basin and channelling it to a single point.• In closed (endorheic) drainage basins the water converges to a single point inside the basin, known as a sink, which may be a permanent lake (e.g. Lake Aral (Aral Sea), Dead Sea, etc.), dry lake (some desert lakes like Lake Chad, Africa), or a point where surface water is lost underground (sinkholes in Karst landforms).”
Why relevant

Identifies Lake Aral (Aral Sea) as a classic example of an endorheic (closed) basin where water converges to a sink; such basins are sensitive to reductions in inflow and can become dry lakes.

How to extend

A student could check a map to confirm the Aral Sea lies in an endorheic basin and then look for evidence that its inflow rivers have been reduced (e.g., by diversion or irrigation) to explain shrinkage.

Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 17: Contemporary Issues > ENVIRONMENTAL AWARENESS > p. 42
Strength: 4/5
“utilisation of the limited natural resources is imperative for the sustainable development and the very survival of humanity. Unfortunately, human activities are transforming the global environment, and these global changes have many faces: ozone depletion, tropical deforestation, acid depositrion, and increased atmospheric concentration of gases that trap heat and may warm the global climate. Human activities now match or even surpass nature as an agent of change in the global environment, as evidenced by a growing list of seemingly diverse human-induced environmental changes that have gripped public attention in recent years. These are as follows: • 1. Rapid changes in the global atmosphere due to fossil fuel combustion and industrial activities predicted to change global climate.• 2.”
Why relevant

States that human activities now rival natural agents of environmental change (e.g., changing atmosphere, land/water use), establishing a general rule that humans can cause large-scale changes to water bodies.

How to extend

Use this general rule plus regional facts (river diversion, irrigation projects) to assess whether human actions could plausibly reduce inflows to the Aral Sea and cause shrinkage.

Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 3: The Drainage System of India > SARASWATI-THE MYSTERY OF A LOST RIVER > p. 28
Strength: 4/5
“Pains; the drying up of glaciers in the Himalayas because of climatic change; rivers piracy; and the shifting in the courses of rivers. All the above studies prove that the Saraswati River in the Vedic Period was moving through Punjab, Haryana, and Rajasthan and was merging into the Arabian Sea.”
Why relevant

Lists mechanisms that can dry rivers/lakes: drying of glaciers, river piracy, and shifting river courses—processes that change freshwater supply to downstream basins.

How to extend

Compare whether the Aral Sea's inflow rivers experienced any of these processes or anthropogenic analogues (e.g., upstream water withdrawals) to evaluate causes of shrinkage.

Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 3: The Drainage System of India > SHIFTING COURSES OF THE RIVERS > p. 24
Strength: 3/5
“Similar shifting has also been observed in the rivers of the Punjab during the historical past. The records of the third century BC show that the Indus flowed more than 130 km east of its present course, through the now practically dry beds of the deserted channel, to the Rann of Kutch which was then a gulf of the Arabian Sea. Later on, it gradually shifted towards the west and occupied its present position. During the reign of Akbar the Great, the Chenab and Jhelum rivers joined the Indus near Uch (Pakistan), but their present confluence lies near Mithankot about 100 km downstream of the old place of confluence.”
Why relevant

Provides historical examples of major river course shifts and diversions in the region (Indus and its tributaries), showing that river courses and their downstream destinations can change substantially over time.

How to extend

A student could locate the Aral Sea and trace historical/current courses of its feeder rivers to test if diversion or course change reduced inflow and led to drying.

Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 3: The Drainage System of India > SARASWATI-THE MYSTERY OF A LOST RIVER > p. 27
Strength: 3/5
“Moreover, Prof. Yas Pal and his colleagues observed a sudden widening of the Ghaggar River near Patiala. They argued that the widening of the Ghaggar River near Patiala was possible only if some major tributary had joined it. According to them, ancient Satadru (Sutlej) swung suddenly westward near Ropar/Rupnagar (Fig. 3.11-B) to join the Indus with its tributaries (Beas and Ravi), deserting its earlier channel to the sea. This sudden diversion of Sutlej as well as depletion of waters from Drishadvati due to loss of its feeding streams, appear to be major events leading to the drying up of Saraswati.”
Why relevant

Describes how diversion or loss of tributaries led to drying of a major river (Saraswati)—an example linking changes in tributary input to downstream drying.

How to extend

Analogously investigate whether tributary diversion or upstream water loss occurred for rivers feeding the Aral Sea, supporting a human-caused shrinkage hypothesis.

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