Explanation

The Western Ghats are the source region of the Godavari (rising at Trimbakeshwar in Maharashtra), the Krishna (rising at Mahabaleshwar) and the Cauvery (rising at Talakaveri in Karnataka) — all three are major east-flowing peninsular rivers originating in the Ghats. The Mahanadi, by contrast, rises in the Dandakaranya region of Chhattisgarh (Sihawa range), not in the Western Ghats. Hence the Mahanadi is the river that does NOT originate from the Western Ghats.