Heavy rains have kept Thervoy Kandigai reservoir brimming since Sunday. In fact, it’s been filled to capacity multiple times since it was commissioned last November. But not a drop from the waterbody — built at a cost of Rs 380 crore to augment Chennai’s drinking water supply — has been used.

That’s because the city’s other reservoirs (Chembarambakkam, Poondi, Red Hills and Cholavaram) already have enough water, says a senior official from the CMWSSB.

But water is still being bought from desalination plants to meet the city’s needs. On Tuesday too, 68 MLD was purchased from the Nemmeli desalination plant, and 45 MLD from the Minjur desalination plant, triggering questions from experts.