Ganga River System

It is the longest river of India. Length ~ 2525km. National aquatic animal in river Ganga is gangetic dolphin. They are blind in nature. Because of the dissolved oxygen in river ganga the dolphins are found, it means some kind of dolphins. Its basin is in 5 states but its drainage area is in 15 states.  That is why it is called National River.  This is purest, longest, polluted, self cleaning. Self-cleaning means a virus is found inside it, it is bacteriophage so it kills the bacteria. Origin - It originates from Bhagirathi which originates from Gangotri glacier.  Which is north of Kashi district which is in Uttarakhand.  The Ganges River flows from - Uttarakhand,  Uttar Pradesh, Bihar, Jharkhand, West Bengal,  Bangladesh.  In fact, I had said 5 earlier, so now counting it is 6.  But Bangladesh does not belong to India.  The drainage basin of the Ganges, it goes into 15 states.

Tributaies:

1. First tributary - Ram Ganga river

2. Last tributary - Mahananda river

3. Longest tributary - Yamuna river (length wise) 

4. Largest tributary - Ghagra river (Meaning most of the water gives Ghagra river)