Read the passage and answer the questions:
WATER POLLUTION
Indiscriminate use of water by increasing population and industrial expansion has led degradation of the quality of water considerably. Surface water available from rivers, canals, lakes, etc. is never pure. It contains small quantities of suspended particles, organic and inorganic substances. When concentration of these substances increases, the water becomes polluted, and hence becomes unfit for use. In such a situation, the self-purifying capacity of water is unable to purify the water. Though water pollutants are also created from natural sources (erosion, landslides, decay and decomposition of plants and animals, etc.) pollutants from human activities are the real causes of concern. Human beings pollute the water through industrial, agricultural and cultural activities. Among these activities, industry is the most significant contributor.
Industries produce several undesirable products including industrial wastes, polluted waste water, poisonous gases, chemical residuals, numerous heavy metals, dust, smoke, etc. Most of the industrial wastes are disposed off in running water or lakes. Consequently, poisonous elements reach the reservoirs, rivers and other water bodies, which destroy the bio-system of these waters. Major water polluting industries are leather, pulp and paper, textiles and chemicals.
Various types of chemicals used in modern agriculture such as inorganic fertilisers, pesticides and herbicides are also pollution generating components. These chemicals are washed down to rivers, lakes and tanks. These chemicals also infiltrate the soil to reach the ground water. Fertiliser induces an increase in the nitrate content of surface waters. Cultural activities such as pilgrimage, religious fairs, tourism, etc. also cause water pollution. In India, almost all surface water sources are contaminated and unfit for human consumption.
Water pollution is a source of various water-borne diseases. The diseases commonly caused due to contaminated water are diarrhoea, intestinal worms, hepatitis, etc. The World Health Organization shows that about one-fourth of the communicable diseases in India are water-borne.
In which of the following conditions does water pollution mainly occur?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → When the concentration of organic and inorganic substance increases.
Option (1) When the water flows from a spring — Incorrect. Flowing from a spring says nothing about how much of these substances the water carries.
Option (2) When the water is collected from wells — Incorrect. The source of the water does not decide pollution; the load of substances in it does.
Option (3) When the concentration of organic and inorganic substance decreases considerably — Incorrect. A fall in these substances makes the water cleaner, not polluted.
Option (4) When the concentration of organic and inorganic substance increases. — Correct. Surface water is never pure: it always carries small quantities of suspended particles and organic and inorganic substances, and its self-purifying capacity can deal with these. When human use adds more and the concentration of these substances increases, that capacity is no longer enough to purify the water, so the water becomes polluted and unfit for use.
Note: This passage is the section ‘Water Pollution’ of the chapter ‘Geographical Perspective on Selected Issues and Problems’ in NCERT India – People and Economy, taken almost word for word. This ‘unseen’ passage on water pollution was a page of the book all along, with the Yamuna table sitting right beside it. Read the tables next to every section, and such a group gives five friendly marks.
Note: A similar question was also asked in CUET (UG) 2026 on 20-05-2026 (Slot 1).
NCERT (2025-26): “Water Pollution … Indiscriminate use of water by increasing population and industrial expansion has led degradation of the quality of water considerably. Surface water available from rivers, canals, lakes, etc. is never pure. It contains small quantities of suspended particles, organic and inorganic substances. When concentration of these substances increases, the water becomes polluted, and hence becomes unfit for use. In such a situation, the self-purifying capacity of water is unable to purify the water.” |