MPSC 2023 Prelims Paper-I · Question 33 of 100

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Deccan, and their catchments are watered by the south-west monsoon between June and September; once that current has withdrawn, very little rain reaches them, and their discharge falls away steeply through the cold season.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.

• (1)The course of the river Kaveri receives heavy rainfall from the south-west monsoons — 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 First, the season is wrong: the south-west monsoon blows from June to September and has withdrawn from the peninsula well before the winter that the stem asks about, so it cannot account for a large volume of water in the cold season.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'.
• (3)The course of the river Kaveri receives rainfall from both south-west and north-east monsoons — 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.
• (4)The tributaries of the Kaveri provide large volume of water to the course of the Kaveri — 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.

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.

Peninsular drainage is examined in MPSC papers both for its own sake and as a way into the rainfall regimes that control it, and questions on the Kaveri almost always turn on the double rainfall it receives, because that is what distinguishes it from every other river in the region. The more general skill this item teaches is how to read a comparative stem. The words 'as compared to the Godavari and Krishna rivers' are not scene-setting; they define the answer, because they restrict it to whatever the Kaveri has that those two lack. A candidate who reads the stem as though it simply asked about the Kaveri will find two options that are true statements about the river and no way to choose between them. Reading it as a comparison eliminates one of those two immediately, since anything the three rivers share cannot be the differentiator. It is a habit worth carrying into every question containing the words 'as compared to', 'unlike', 'in contrast with' or 'more than': write down what the two sides have in common, strike out every option built from it, and the field usually reduces to one.

• The upper catchment of the Kaveri receives rain from the south-west monsoon and its lower catchment from the north-east monsoon, so the river carries water through the year with comparatively less fluctuation than any other peninsular river.
• The north-east monsoon of October to December gives the Coromandel coast and interior Tamil Nadu their principal rainfall, because the offshore winter winds cross the Bay of Bengal and take up moisture before striking the coast.
• The Godavari and Krishna basins lie largely in the interior Deccan and depend almost entirely on the south-west monsoon, so their discharge falls away sharply once that current has withdrawn.
• Peninsular rivers are rain-fed and therefore markedly seasonal, unlike the Himalayan rivers, which are supplied by snow and glacier melt in addition to rain and so flow through the year.
• The Kaveri rises at Talakaveri in the Brahmagiri hills of Kodagu district in Karnataka and flows south-eastwards across Karnataka and Tamil Nadu to the Bay of Bengal, where it builds a large delta.

• Answering a comparative stem with a factor that all the compared items share, which explains none of them; the south-west monsoon feeds all three rivers named here
• Choosing a true statement about the subject when the stem asks for the specific difference, which is how a factually correct option becomes the wrong answer
• Forgetting that the south-west monsoon has withdrawn from the peninsula long before the winter season the question is about
• Treating tributaries as a source of water rather than as channels that deliver rain which must first have fallen in the catchment

River questions in MPSC papers ask for sources and mouths, tributaries and their confluences, the states a basin covers, the dams built on a river, and the regime of its flow. The regime questions are the ones that carry reasoning, and the Kaveri appears in them more often than its size warrants because its double rainfall makes it the natural test case. Expect the commission to frame such items as comparisons, since a comparison lets it place several true statements in the option set and separate candidates on precision rather than on knowledge. The related topics likely to appear alongside are the north-east monsoon, the rain shadow of the Ghats, the seasonality of peninsular rivers against the perennial Himalayan ones, and the water disputes that follow from an unevenly distributed supply.

No directly related past PYQ was found.

• practice — not a real PYQ

  The Kaveri river rises at Talakaveri, in which of the following ranges or hills ?

  • (a)The Brahmagiri hills of Kodagu in Karnataka
  • (b)The hills near Mahabaleshwar in Maharashtra
  • (c)The hills near Trimbakeshwar in Nashik district
  • (d)The Amarkantak plateau in Madhya Pradesh

  Answer(a) The Brahmagiri hills of Kodagu in Karnataka — the Kaveri rises at Talakaveri on the eastern slope of the Western Ghats and flows south-east to the Bay of Bengal. Mahabaleshwar is the source of the Krishna, Trimbakeshwar near Nashik that of the Godavari, and the Amarkantak plateau that of the Narmada and the Son, so the four options together cover the sources most often confused with one another.

• practice — not a real PYQ

  Which of the following best explains why the Himalayan rivers flow through the year while most peninsular rivers do not ?

  • (a)The Himalayan rivers have much larger catchment areas
  • (b)The Himalayan rivers are fed by snow and glacier melt in addition to rainfall
  • (c)The Himalayan rivers flow through softer rock and so cut deeper channels
  • (d)The Himalayan rivers receive rain from both the monsoons

  Answer(b) The Himalayan rivers are fed by snow and glacier melt in addition to rainfall — the melt continues through the dry months and even peaks in summer before the monsoon arrives, so the channels never run dry. Peninsular rivers depend on rain alone and therefore shrink sharply once the monsoon withdraws. Catchment size and rock type affect the volume and the valley form but cannot supply water in a season when none is falling.