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 statements are NOT true according to the passage?
(A) The Bhagirathi begins at the lower end of the Gangotri glacier.
(B) The melt from a glacier keeps rising for as long as the glacier goes on shrinking.
(C) During the monsoon, rain supplies so much water that the plains depend little on glacier melt.
(D) People living below a glacial lake usually get several days’ notice before an outburst flood.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (B) and (D) only
The question asks for the statements that are NOT true.
(A) The Bhagirathi begins at the lower end of the Gangotri glacier. — True.
- The Bhagirathi “flows from the snout of the Gangotri glacier”.
- The snout is the lower end of a glacier.
(B) The melt from a glacier keeps rising for as long as the glacier goes on shrinking. — Not true.
- After ‘peak water’, “the melt begins to fall” even though the ice is still shrinking.
(C) During the monsoon, rain supplies so much water that the plains depend little on glacier melt. — True.
- During the rains the plains “hardly need the glaciers, since rainfall dwarfs their share”.
- To dwarf is to make something look small.
(D) People living below a glacial lake usually get several days’ notice before an outburst flood. — Not true.
- The lake “can empty within hours”, and the flood comes “with little warning”.