The train will ferry water to parched Chennai, which needs 830 million litres a day.

The first train carrying water to parched Chennai is likely to leave from Jolarpet railway station on Friday. "The wagons have been filled. We are waiting for clearance to leave from Chennai Metro Water," a senior railways officer told NDTV.

A function has been planned at the Villivakkam railway station to receive the first water train. State minister S P Velumani and few other ministers are expected to attend.

Fifty wagons of this train with a capacity of 50 kilolitres each would transport 2.5 million litres each trip. With two trains available for this purpose, the railway authorities are trying to supply at least 7.5 million litres a day to begin with, though the target is 10 million litres.

"Based on slots available for movement of these trains the capacity could go up," said the officer.

Southern Railways would charge Chennai Metro Water Rs 7.5 lakh for each trip. The Tamil Nadu government has allotted Rs 65 core for this project.

Officials say these trains would take around five hours to reach Chennai's Villivakkam, 220 km away, from where water would be pumped to the Kilpauk Water Works, the pumping station that distributes water to localities in the city.

However, the water supply by train would not increase supply to Chennai. It will only ease the pressure on the state government to ensure a minimum supply of 525 million litres to residents against the requirement of 830 million litres a day.

A 3.5-km-long pipeline was laid connecting the Jolarpet railway station with a pumping house. A trial run of the supply line was carried out on Wednesday.

Blaming four parched drinking water supplying reservoirs outside Chennai due inadequate monsoon last year, Chennai Metro Water has cut piped water supply by 40 per cent. In many areas, residents don't get piped water at all.

Chennai Metro Water has deployed 900 tankers for street supply. Many families say they get five pots of water daily from the tankers. Private water tankers have doubled the price since April. The Madras High Court has criticised the Tamil Nadu government for not doing enough.

Chennai is one of the 20 Indian cities that the government think tank NITI Aayog has said would run out of water by 2021.