As compared to the Godavari and Krishna rivers, the course of the Kaveri river receives large volume of water during winter, because

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Correct — option (2). The stem is a comparison, and a comparison can only be answered by the factor that differs between the things compared. All three rivers named are peninsular rivers, all three are rain-fed rather than snow-fed, and all three are therefore at the mercy of whatever rain falls in their catchments. The Godavari and the Krishna drain the interior of the Deccan, and their catchments are watered by the south-west monsoon between June and September; once that current has withdrawn, very little rain reaches them, and their discharge falls away steeply through the cold season. The Kaveri is different in one specific respect. Its lower basin lies in Tamil Nadu, and Tamil Nadu sits in the rain shadow of the Western Ghats during the south-west monsoon but receives its principal rainfall in October, November and December from the north-east monsoon. In that season the winds blow outward from the cooling landmass of northern India, and the branch that passes over the Bay of Bengal picks up moisture before turning on to the Coromandel coast, where it delivers rain directly. So at precisely the time of year when the Godavari and the Krishna are receiving nothing, the Kaveri's lower catchment is being rained on. That is why the Kaveri carries a large volume of water in winter while the other two do not. It also explains a feature of the Kaveri that is worth remembering in its own right: because its upper catchment in Karnataka and Kerala is fed by the south-west monsoon and its lower catchment by the north-east monsoon, the river carries water through the year with markedly less fluctuation than any other peninsular river, which is what has made its water so valuable and so bitterly contested. Option (2) names the north-east monsoon, the one source of water that the Kaveri has and the Godavari and Krishna effectively do not.

Why the other options are wrong — (a) The Kaveri's upper catchment, in the Western Ghats of Karnataka and Kerala, genuinely does receive heavy south-west monsoon rain, so this option is not false as a statement about the river. It fails on two counts as an answer. First, the season is wrong: the south-west monsoon blows from June to September and has withdrawn from the peninsula well before the winter that the stem asks about, so it cannot account for a large volume of water in the cold season. Second, and more fundamentally, the south-west monsoon is exactly what the Godavari and the Krishna live on too, so it is the factor the three rivers share. A shared factor can never explain a difference between them. This is the standard way a comparative stem is failed — by answering the question 'where does this river get its water' instead of the question 'why does this river differ from those'.  (c) As a description of the Kaveri this option is accurate, and that is what makes it the most attractive of the three: the upper basin is watered by the south-west monsoon and the lower basin by the north-east monsoon, which is precisely why the river's flow is steadier than that of its neighbours. But the stem does not ask what waters the Kaveri; it asks why the Kaveri carries a large volume in winter as compared with the Godavari and the Krishna, and an answer to a comparative question has to isolate the difference. The south-west monsoon half of this option is common to all three rivers, so including it dilutes rather than sharpens the explanation, and the south-west monsoon contributes nothing at all in the season under discussion. Strip out what the three rivers share and what remains is the north-east monsoon alone, which is option (2). When a comparative stem offers both the shared factor and the distinguishing one, the distinguishing one is what is being asked for.  (d) This option names a conduit and calls it a source. Tributaries deliver water to a main stem, but they do not create it; every drop they carry must first have fallen as rain somewhere in the catchment, so an explanation that stops at the tributaries has simply moved the question one step upstream without answering it. The comparison also defeats the option on its own terms. The Godavari is the largest of the peninsular rivers and has a longer list of tributaries than the Kaveri, and the Krishna's tributary system is likewise extensive; if a river's winter volume were decided by the number of streams feeding it, the Godavari would be the one carrying water in the cold season. It is not, because its tributaries drain a region that receives no rain at that time of year. What matters is not how many channels a river has but whether rain is falling into them.

Concept: India has two monsoons, and the second is easy to underrate because it matters over so small a part of the country. The south-west monsoon of June to September supplies the overwhelming bulk of the country's rain and dominates every account of Indian climate. The north-east monsoon of the cold weather season blows outward from the high pressure that builds over the northern landmass, and over most of India it is a dry offshore wind. Its exception is the branch that crosses the Bay of Bengal: passing over warm water it takes up moisture, and when it reaches the Coromandel coast and the interior of Tamil Nadu it delivers that moisture as rain in October, November and December. The result is a corner of India whose rainfall calendar is out of step with the rest of the country, receiving its principal rain when the rest of the peninsula is drying out. This has consequences for the rivers. Peninsular rivers are rain-fed and therefore seasonal, in contrast to the Himalayan rivers, which draw on snow and glacier melt as well and remain perennial. Among the peninsular rivers the Kaveri is the closest to an exception, because its basin straddles both rainfall regimes: the upper catchment in the Western Ghats is filled by the south-west monsoon and the lower catchment in Tamil Nadu by the north-east monsoon, so the river carries water through the year with comparatively little fluctuation.

State PCS 2023 Q33 — Geography PYQ with Answer

State PCS 2023 Q33 — Geography PYQ with Answer