A special 50 wagon train carrying water from Tamil Nadu's Vellore district will reach Chennai on Friday afternoon, a Southern Railway official said.
According to the official, each wagon has capacity to carry 50,000 litres of water.
The train was flagged off from the Jolarpettai station in the morning.
State Ministers were likely to be present at the inauguration of the unloading of the water at Villivakkam station.
Earlier, Tamil Nadu Chief Minister K. Palaniswami had announced the state government's plans to transport 10 million litres of water daily by rail from Jolarpettai to meet the needs of parched Chennai.
He said a sum of ₹65 crore had been allocated for this purpose.
Currently the Chennai Metropolitan Water Supply and Sewerage Board (Chennai Metro Water) is supplying about 525 million litres per day (MLD) in the state capital. The water from Jolarpettai will augment the existing supply.
While the Cholavaram (full capacity 1,081 mcft) and Redhills (full capacity 3,300 mcft) reservoirs and Chembarambakkam lake (full capacity 3,645 mcft) that supply water to Chennai have run dry, 16 mcft water is left in the Poondi reservoir (against a full capacity of 3,231 mcft), according to the Chennai Metro Water.