Sri Lanka has marked a major milestone in its irrigation history with the successful completion of excavation work on South Asia’s longest irrigation tunnel, officials said.

The 27.7-kilometre tunnel, constructed under the North Central Province Canal Project — a key component of the Mahaweli Master Plan — was completed following a major underground breakthrough involving two advanced Tunnel Boring Machines.

The excavation, which began simultaneously from Maha Meegaswewa and Koduruwawa, concluded when the two tunnel sections met beneath the ground, a major engineering achievement known as a “Tunnel Breakthrough.”

The tunnel is being developed under the Mahaweli Water Security Investment Programme with financial support from the Asian Development Bank and is expected to become the longest irrigation tunnel in South Asia.

The North Central Province Canal Project, stretching nearly 240 kilometres, is designed to enhance water distribution across the region by supplying 1,505 reservoirs linked to 12 major irrigation systems and 130 cascade networks.

Authorities said the project will provide direct benefits to around 25,000 families and support cultivation across 74,000 hectares of agricultural land during both the Yala and Maha seasons.

The initiative is also aimed at improving access to clean drinking water in the Rajarata region, where communities have faced a long-standing challenge from chronic kidney disease of unknown origin.

Once completed, the project is expected to release around 70 million cubic metres of water annually, helping meet the drinking water needs of nearly 1.5 million people.