Q. The Narmada river flows to the west, while most other large peninsular rivers flow to the east. Why?

1. It occupies a linear rift valley.
2. It flows between the Vindhyas and the Satpuras.
3. The land slopes to the west from Central India.

Select the correct answer using the codes given below. (UPSC Prelims 2013)
Answer: 1 only
Notes: The correct answer is [A] 1 only.This question addresses a unique geological anomaly in the Indian drainage system. While most major peninsular rivers (like the Godavari, Krishna, and Kaveri) follow the general plateau slope toward the Bay of Bengal, the Narmada and Tapi defy this trend.

• 1. It occupies a linear rift valley: (Correct) The primary reason the Narmada flows west is that it flows through a rift valley (a graben) formed by the subsidence of a land block between two parallel faults. This structural depression was created during the upheaval of the Himalayas. The river is essentially "trapped" in this valley, which tilts toward the West, forcing the water to flow into the Arabian Sea.
• 2. It flows between the Vindhyas and the Satpuras: (True, but not the reason) It is a geographical fact that the Narmada flows between the Vindhya range (to the north) and the Satpura range (to the south). However, simply being between two ranges doesn't explain the direction of flow. It is the rift valley structure within these ranges that dictates the westward movement. In multiple-choice questions of this nature, you must distinguish between a fact and a causal reason.
• 3. The land slopes to the west from Central India: (Incorrect) The general slope of the Indian Peninsula is actually from West to East. This is why the Western Ghats are higher than the Eastern Ghats and why most rivers flow toward the Bay of Bengal. The Narmada is an exception because it follows the local slope of the rift valley, not the general slope of the subcontinent.