Though Inland waterways were the chief mode of transport before the advent of railways in India, what made them non-navigable in large parts of their courses?

Diversion of river water for irrigation purposes.

The correct answer is Option 1: Diversion of river water for irrigation purposes.

NCERT: Inland waterways- It was the chief mode of transport before the advent of railways. It, however, faced tough competition from road and railway transport. Moreover, the diversion of river water for irrigation purposes made them non-navigable in large parts of their courses. India has 14,500 km of navigable waterways, contributing about 1% to the country’s transportation. It comprises rivers, canals, backwaters, creeks, etc. At present, 5,685 km of major rivers are navigable by mechanised flat-bottom vessels.