Colombo completes South Asia’s longest irrigation canal

The investment for the MWSIP totals around 0 million, partly funded by the ADB. It is 96 km long and forms part of a wider project to transform one of the island’s driest regions by channelling water from the Mahaweli River. Once completed, it will irrigate 43,000 hectares of land during the Yala and Maha seasons.

Colombo (AsiaNews) - The longest irrigation tunnel in South Asia is due to be completed by the end of the month; according to the designers, it will breathe new life into an area renowned for being one of the driest in the country.

The total investment for the Mahaweli Water Security Investment Programme (MWSIP) amounts to approximately 0 million, thanks in part to funding allocated over time by the Asian Development Bank (ADB), which has been essential for completing the project. Fifty-six per cent of the total sum is earmarked for the construction of the 27-kilometre-long tunnel for the North Central Province Canal Project (NCPCP).

The 96-km mega-irrigation tunnel in the North Central Province forms part of the wider Maha Ela project, designed specifically to transport water from the Moragahakanda reservoir to Mahakanadarawewa.

Due to the hilly terrain at Palugaswewa and Mahameegaswewa, a section of the canal has been constructed via a tunnel. The construction cost of the structure is expected to amount to approximately 49 billion rupees (equivalent to around 126 million euros).

Meanwhile, as part of phases one and two of the project, around four million euros have been allocated for the implementation of a wildlife management plan aimed at protecting biodiversity and mitigating human-elephant conflict in the affected areas.

This includes the enhancement and development of 650 hectares of grassland habitat, as well as the construction of 160 kilometres of electric fencing for elephants in the region.

The main objective of the MWSIP is to channel excess water from the Mahaweli River, which covers a catchment area of 10,256 km², to water-scarce regions in the North Central, Northern and Eastern provinces.

It is the longest river in Sri Lanka, stretching 345 kilometres and collecting water from wet, intermediate and dry zones. The river represents a major climate mitigation resource, supported by large storage reservoirs and diversion channels along its course from Horton Plains (Central Province) to its outlet at Trincomalee (Eastern Province).

Udaya Ranathunga, project director, said: “The main features of the Mid-North Province Canal Project (MWSIP) include a 96-kilometre canal system with a 28-kilometre tunnel. Added to this is a 30.3 km transfer canal extending from Yakalla to Mahakanadarawa, as well as the 8.8 km Kaluganga–Moragahakanda transfer canal. The expert adds that the project is expected to “supply 40 million cubic metres of drinking water per year to around 25,000 households, benefiting seven major reservoirs”.

Civil engineers Damayanthi Kasturiarachchi and Randesh Sirimanne explain to AsiaNews that “once completed, the tunnel will convey excess water from the Moragahakanda and Kaluganga reservoirs to the arid zone. The tunnel runs underground from Konduruwawa/Elahera to Mahameegaswewa/Palugaswewa.

It forms part of a wider 96-km water conveyance mega-project overseen by Mahaweli Consultancy and the NCPCP. This tunnel,” they conclude, “will convey 40 cubic metres of water per second. Once completed, it will irrigate 43,000 hectares of land during the Yala and Maha seasons [the two main seasons, governed by the monsoons], supplying water to over 1,200 small reservoirs.

Bharatha Senanayaka and Amendra Tennakoon, leading experts in the field, emphasise that “once the North-Central Province canal is completed, Sri Lanka will be able to utilise approximately one billion cubic metres of water that currently flows into the sea.

Completion of the project will also mark the culmination of one of the most complex and essential water resource development initiatives, transforming the arid northern zone into a region for export-oriented fruit and vegetable production. Furthermore, it will strengthen rural livelihoods, create employment for young people and improve – they warn – climate resilience in the country’s agri-food sector”.

In 1976, the diversion of the Mahaweli River brought about a radical transformation, significantly altering the biodiversity and the surrounding environment of Anuradhapura and the arid Kala Oya basin in the North Central Province. The project brought about a substantial transformation, creating a greener urban environment, whilst the Rajangana reservoir, previously water-scarce, became rich in water resources.

A similar transformation is expected in the area served by the North Central Province Canal, which covers approximately 500,000 hectares in one of Sri Lanka’s driest regions. With water diverted to this region, the environment is expected to change significantly, with five major rivers becoming perennial systems.

“Subsequently,” the researchers conclude, “the entire area could be transformed into a commercial agricultural zone whilst establishing itself as a tourist hub similar to the Habarana tourism development zone in Polonnaruwa. This is an achievable goal thanks to the diversion of water through the Huruluwewa feed canal and the replenishment of the Minneriya and Kandalama reservoirs.”