Perennial and non-perennial rivers
Also called: Perennial and ephemeral rivers · Topic: Drainage System of India: Rivers, Basins and Patterns · NCERT: Class 11, Ch 3 "Drainage System"
Meaning
A perennial river flows all year round. A non-perennial or ephemeral river flows mainly in the rainy season and shrinks or dries up in other months. The difference comes from where the water comes from. Himalayan rivers get both melting snow and monsoon rain, so they never run dry. Most Peninsular and desert rivers depend only on rain. This matters for irrigation, drinking water and hydropower all through the year.
Example
The Ganga, fed by the Gangotri glacier and the monsoon, flows all year. In Rajasthan the Luni is wholly ephemeral: it carries water only after rain and is dry for most of the year.
Don't confuse with
- Seasonal variation in flow: perennial rivers also rise and fall with the seasons. The Ganga peaks in August–September, for example. Being perennial only means the river never fully dries up.
- Exceptions in the Peninsula: the Narmada and Tapi, which flow in rift valleys, are exceptions to the usual non-perennial pattern. The Kaveri gets both the southwest and northeast monsoons, so its flow changes less than that of any other Peninsular river.
Related concepts
- Peninsular drainage system
- Evolution of the Peninsular drainage
- East-flowing rivers of the Peninsula