Indian rivers fall into two families. Himalayan rivers - the Indus, Ganga and Brahmaputra - are snow-fed and perennial, cutting deep gorges and forming large plains. Peninsular rivers are rain-fed and seasonal.
The Ganga is India's longest river at about 2,525 km, rising at Gangotri and joined by the Yamuna at Prayagraj. The Godavari, the longest peninsular river, is called the Dakshina Ganga.
The Narmada and Tapi are unusual in flowing west into the Arabian Sea through rift valleys, which is why they form estuaries rather than deltas.