RAS question
The 50 cm isohyet line in Rajasthan approximately follows:
Correct answer: (D) The Aravalli Range.
In Rajasthan, the 50 cm isohyet approximately follows the Aravalli Range, marking the broad rainfall divide between the drier west and the wetter east.
Explanation
An isohyet joins places receiving the same amount of rainfall, so the 50 cm isohyet is a climatic line rather than an administrative or transport line. In Rajasthan, this line lies roughly along the Aravalli Range, separating the arid western side, which receives less than 50 cm rainfall, from the semi-arid and sub-humid eastern side, which receives more than 50 cm. The Testbook solution notes the same core point: the 50 cm isohyet line is present along the Aravalli and divides Rajasthan into two parts. That is why the Aravalli Range, not a canal, latitude line, or state boundary, is the best approximate match.
Why the other options are wrong
- (A) The IGNP canal route lies in western Rajasthan, while the 50 cm isohyet is described as a climatic divide along the Aravalli Range.
- (B) The Tropic of Cancer is much farther south, whereas the 50 cm isohyet is tied here to Rajasthan's Aravalli-based rainfall divide.
- (C) The Madhya Pradesh boundary is on the eastern side of Rajasthan, but the 50 cm isohyet separates the arid west from the wetter east within Rajasthan.
Concept
This tests Rajasthan climatology, especially the use of isohyets to read regional rainfall patterns. It recurs in RAS because the Aravalli-linked rainfall divide explains Rajasthan's sharp west-east contrast in aridity.