The watershed lies mostly in eastern Vidarbha region of Maharashtra state and is nearly 18,929 km².
It originates in Pokharni Village which is 2 km away from Bhainsdehi. Bhainsdehi is a thasil place in Betul district Madhya Pradesh adjoining Amravati district of Maharashtra and flows through Akola, Buldhana, and Jalgaon districts. Total length of Purna River is 334 km.
The word purna means complete in Sanskrit. Purna River was also called as Payoshni or Paisani. It is Sanskrit word meaning ambrosia. There are other rivers too, viz. Khadakpurna, Katepurna, referred to as Purna.