Read the passage and answer the questions given below it.
A river fed by ice can look its healthiest just when its future is least secure. That is the puzzle of the Himalayan glaciers. The Bhagirathi, a headstream of the Ganga, flows from the snout of the Gangotri glacier, and many northern rivers draw on ice in their upper reaches. Survey after survey finds that most Himalayan glaciers are thinning and retreating.
Retreat, oddly, does not at first mean less water. A glacier that melts faster sends more water downstream, so a river may run fuller for years while the ice that feeds it shrinks. Scientists call the turning point ‘peak water’. After it, the melt begins to fall, because less ice is left to melt. The extra flow is not a sign of health. It is a store being spent.
Nor does this matter most in the monsoon. During the rains, the plains hardly need the glaciers, since rainfall dwarfs their share. It is in the hot, dry weeks before the monsoon, when fields are parched, that meltwater attenuates the effects of the shortage. The Indus basin, with its drier lowlands, leans on this supply far more heavily than the Ganga basin, where rain carries more of the load.
Retreat brings a quicker danger too. Meltwater often pools in lakes behind loose walls of rock and debris left by the glacier. If such a wall gives way, the lake can empty within hours, and the flood that follows, a glacial lake outburst flood, tears down the valley with little warning. None of this means the rivers will soon run dry. When peak water arrives differs from basin to basin, and for some rivers no one can yet say whether it has already passed.
Which of the following can be inferred from the passage?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → A river fed by a glacier may run fuller even while it is losing its source.
The second paragraph leads straight to this idea, one step beyond its words.
- The passage says a river “may run fuller for years while the ice that feeds it shrinks”. The ice is the river’s source, the place its water comes from.
- It adds that the extra flow “is not a sign of health”. So a fuller river does not prove that its glacier is safe. It may be losing the very ice it depends on.
Why the Other Options are Incorrect?
Option 2: Once peak water has passed, the meltwater reaching the plains in the dry weeks should slowly recover. — Incorrect. Contradicted: After peak water, “the melt begins to fall, because less ice is left to melt”. Nothing in the passage says it will recover.
Option 3: A failure of meltwater in the dry weeks would hurt the Ganga basin more than the Indus basin. — Incorrect. Contradicted: The Indus basin leans on meltwater “far more heavily than the Ganga basin”. So the Indus basin would be hurt more.
Option 4: Scientists have now worked out when peak water will arrive for most Himalayan rivers. — Incorrect. Contradicted: The last line says that for some rivers “no one can yet say” whether peak water has already passed.