Ganga is an outlier when it comes to how polluted it is. Most water sources with settlements nearby aren't safe for drinking but most river's tributaries are re

Ganga is an outlier when it comes to how polluted it is. Most water sources with settlements nearby aren't safe for drinking but most river's tributaries are relatively clean and safe for drinking (after some processing). According to wikipedia: "The Ganges suffers from extreme pollution levels, caused by the 400 million people who live close to the river". South Indian rivers are much, much more cleaner but almost all of it used for irrigation.