The reason for the high variability of rainfall in the northwestern part of Madhya Pradesh is:
- (a)Low rainfall.
- (b)High rainfall.
- (c)High temperature.
- (d)Continuous rainfall.
Correct — A, low rainfall. Rainfall variability is measured as the coefficient of variation, C.V. = (standard deviation ÷ mean rainfall) × 100. The mean sits in the denominator, so the smaller a region's average rainfall, the larger the percentage swing produced by the same absolute departure. The relationship is inverse and it holds across India: areas receiving over 100 cm a year show variability under 25 per cent, areas receiving 50–100 cm show 25–50 per cent, and areas receiving under 50 cm show over 50 per cent. Physically, a dry region lies at the outer margin of monsoon penetration and depends on a handful of depressions reaching it — miss two of them and the season collapses, whereas a wet region has so many rain-days that one weak spell barely dents the total. North-western Madhya Pradesh (the Gwalior–Chambal tract of Bhind, Morena, Sheopur and Datia) is the driest corner of a state whose rainfall falls steadily from the south-east to the north-west, which is precisely why its rainfall is the least dependable.
- (b)High rainfall. — The exact inverse of the truth. India's least variable rainfall — under 25 per cent — is found on the west coast, the Western Ghats and in the north-east, i.e. the regions of heaviest rainfall. Abundant rain means many rain-days and a dependable total.
- (c)High temperature. — North-western MP is genuinely hot in summer, which makes this tempting, but temperature is a companion of aridity, not the measure behind variability. Coastal and north-eastern India are also hot yet have the country's most dependable rainfall — so high temperature by itself does not produce high variability.
- (d)Continuous rainfall. — Continuous, steady rain is the signature of low variability, not high. The north-west of the state receives its rain in a few short bursts from passing monsoon depressions rather than continuously, and it is that dependence on a small number of spells which makes the total erratic.
Rainfall has two separate attributes — how much and how dependable. Dependability is expressed by the coefficient of variation of annual rainfall, C.V. = (standard deviation ÷ mean) × 100, which reports the departure from the long-term average as a percentage. Because the mean is the divisor, variability rises as mean rainfall falls, so India's driest regions are also its most unreliable ones. This is why drought is a recurring feature of low-rainfall belts such as western Rajasthan and the interior Deccan, and why irrigation, not just rainfall totals, decides agriculture there.
Within Madhya Pradesh, rainfall declines from the south-east to the north-west: the south-eastern districts around Balaghat, Mandla, Dindori and Anuppur are the wettest, fed generously by the Bay of Bengal branch of the monsoon, while the Gwalior–Chambal corner in the north-west is the driest and gets only the weakened tail of the monsoon currents. Once you know that gradient, the question answers itself — the north-west is the low-rainfall end, and low rainfall is what makes rainfall variable. Option (c) is the designed trap because heat and dryness travel together in students' minds; the fix is to remember that variability is a statistic about rainfall, computed from rainfall, so its cause must be a rainfall property.
- Rainfall variability = coefficient of variation = (standard deviation ÷ mean rainfall) × 100
- Annual rainfall over 100 cm → variability under 25 per cent (west coast, Western Ghats, north-east India, Ganga plain's eastern part)
- Annual rainfall 50–100 cm → variability of 25–50 per cent (most of India)
- Annual rainfall under 50 cm → variability over 50 per cent (western Rajasthan, interior Deccan, parts of the cold north)
- In Madhya Pradesh rainfall decreases from the south-east (Balaghat–Mandla–Dindori, the wettest) towards the north-west (Gwalior–Chambal, the driest)
Because the mean rainfall is the divisor in the coefficient of variation, less rain always means less reliable rain.
- Reading 'variability' as 'quantity' — a region can have low rainfall and high variability at the same time; the two are different measurements
- Blaming high temperature for erratic rainfall — hot and wet regions such as the Kerala coast have among India's most dependable rainfall
- Assuming the whole of Madhya Pradesh is uniformly rainy because the Narmada basin is well watered
MPPSC asks the MP-specific version — which part of the state receives the most or least rainfall, which monsoon branch feeds the south-east, which statement about the state's climate is wrong. UPSC asks the same physical principle in national terms, usually as a statement pair on the direction in which rainfall or monsoon duration changes across India.
Consider the following statements: 1. The duration of the monsoon decreases from southern India to northern India. 2. The amount of annual rainfall in the northern plains of India decreases from east to west. Which of the statements given above is/are correct?
- (a) 1 only
- (b) 2 only
- (c) Both 1 and 2
- (d) Neither 1 nor 2
Answer(c) Both 1 and 2 — the monsoon is shorter as you go north, and rainfall falls off westwards across the northern plains.
The same underlying idea in national form — rainfall thins out as you move away from the moisture source and as the monsoon's stay shortens; that dry, briefly-served end of the gradient is exactly where variability is highest.
Which of the following statements about the climate of Madhya Pradesh is NOT correct?
- (a) During winter, the northern parts become cooler than the southern parts.
- (b) The south-eastern part of the state receives relatively higher rainfall.
- (c) Temperature remains low in Morena and Datia districts during summer season.
- (d) Generally, the winter season is dry.
Answer(c) Temperature remains low in Morena and Datia districts during summer season.
Tests the same climatic profile of northern MP that this question rests on — the south-east is the wet end, and the Datia–Bundelkhand belt of the north is the hot, dry end.
Which of the following districts receives higher rainfall during the rainy season?
- (a) Narsinghpur
- (b) Mandsaur
- (c) Mandla
- (d) Chhatarpur
Answer(c) Mandla
The same south-east-to-north-west rainfall gradient, asked district-wise; knowing that Mandla is the wet end tells you the Chambal districts are the dry — and therefore the most variable — end.
- practice — not a real PYQ
In India, areas receiving an annual rainfall of less than 50 cm generally record a rainfall variability of:
- (a)Less than 25 per cent
- (b)25 to 50 per cent
- (c)More than 50 per cent
- (d)Variability cannot be computed for such areas
Answer(c) More than 50 per cent — the driest belts, such as western Rajasthan and the interior Deccan, are also the most erratic.
- practice — not a real PYQ
Which part of Madhya Pradesh receives the highest annual rainfall?
- (a)The Gwalior–Chambal region
- (b)The Malwa plateau
- (c)The south-eastern districts such as Balaghat, Mandla and Dindori
- (d)The Bundelkhand region
Answer(c) The south-eastern districts — rainfall in the state declines from the south-east towards the north-west.