Concept:
River valley projects and major dams form an essential part of geographical studies. Mettur Dam is one of the largest and oldest dams constructed in India, situated in the Salem district of Tamil Nadu.
Step 1:
The Mettur Dam was completed in 1934 and is constructed across the Kaveri River (Cauvery) as it enters the flat plains region. It creates the vast Stanley Reservoir and serves as a vital irrigation asset for delta agriculture downriver.
Step 2:
Verifying the other river options: Bhavani is a tributary of Kaveri, the Krishna river hosts the Nagarjuna Sagar and Almatti dams, and the Vaigai river has the Vaigai Dam across it. Hence, Kaveri is the correct match for Mettur Dam.