RAS question
The Thar Desert in western Rajasthan receives an average annual rainfall of approximately:
Correct answer: (A) Less than 25 cm.
The core Thar Desert in western Rajasthan receives less than 25 cm of average annual rainfall.
Explanation
The question is asking about the core desert belt, not Rajasthan's wider dry or semi-arid zone. Jaisalmer, Barmer, western Jodhpur and Bikaner fall in this core Thar Desert belt, which receives less than 25 cm, or 250 mm, of annual rainfall. MaargX UPSC by SAARTHI IAS divides the Thar Desert by rainfall into an Arid or Rathi Region with 0-25 cm rainfall and a Semi-Arid or Bangar Region with 25-50 cm rainfall. It also identifies the 25 cm isohyet as the line separating the arid and semi-arid parts. So, for the core western desert, the best answer is less than 25 cm.
Why the other options are wrong
- (B) 25-50 cm belongs to the semi-arid Bangar transition belt, while the core arid Thar/Rathi belt is below the 25 cm isohyet.
- (C) 50-100 cm points to sub-humid eastern Rajasthan, not the low-rainfall core of the western Thar Desert.
- (D) More than 100 cm is associated with the wetter south-eastern Rajasthan belt, not Jaisalmer-Barmer-style arid desert conditions.
Concept
This tests Rajasthan physical geography, especially rainfall isohyets and the arid versus semi-arid division of the Thar Desert. It recurs in RAS because rainfall thresholds help classify regions, agriculture, vegetation and desert landscapes in western Rajasthan.