The Rs10.05 billion diversion tunnel of the Sunkoshi Marin multipurpose project, a hope for the people of the perennially parched central Tarai, achieved a breakthrough on Wednesday, six months before its completion deadline.

The 13.3-km diversion tunnel will redirect part of the flow of the Sunkoshi River to the Marin River, a tributary of the Bagmati River, to irrigate farmlands in the central Tarai. The construction site is located in Sindhuli district, about 120 km southeast of Kathmandu on the BP Highway.

The final point of the tunnel was broken in the presence of Prime Minister Pushpa Kamal Dahal amid a function on Wednesday.

The Rs87 billion Sunkoshi Marin project located in Sindhuli and Ramechhap districts aims to harness water from the Sunkoshi River, directing it into the Bagmati River to irrigate 122,000 hectares of farmland in Rautahat, Dhanusha, Mahottari, Sarlahi and Bara districts in the southern plains.

According to Mitra Baral, the project chief, the hydropower component is expected to cost Rs49.42 billion, from the earlier estimated Rs46.19 billion, which includes the construction of the tunnel, headworks, powerhouse and transmission line, river management, and capacity building works.

The irrigation scheme, estimated to cost Rs37.3 billion, also may see a variation when the detailed project report is completed, according to project officials.

The project, which got the status of a national pride project on January 20, 2020, has a completion deadline of July 2027.

The defects liability period is two years, during which the contractor is legally required to return to the construction site to repair any defects which appear in the contractor’s work since the date of completion.

The project proposes to build a 12-metre-high barrage across the Sunkoshi River and divert a discharge of 67 cubic metres a second through the tunnel to Kusumtar located in ward 6 of Kamalamai Municipality in Sindhuli district.

A powerhouse will be built on the Marin River to generate 31.07 megawatts of electricity.

The installed capacity of the hydropower project was initially set at 42.3 megawatts. During the feasibility study, planners decided that a 31.07 megawatt project would be most economical and viable.

According to Baral, they have planned an additional 10 MW cascade project from the Marin river.

Prime Minister Dahal said that the completion of the national pride project would irrigate a swathe of land in the Tarai and open up economic opportunities.

“This project will provide year-round irrigation to farmlands of five districts of the Madhesh province, and will contribute to the economy and also generate hydropower.”

As agriculture is the backbone of the Nepali economy, with a share of about a fourth of the GDP, Dahal said increased agricultural production would help the country be self-sufficient in food.

“Increased productivity will also help narrow down the ballooning trade deficit,” the prime minister said.

In February 2021, the China Overseas Engineering Company won the contract for the construction of the tunnel for the Sunkoshi Marin multipurpose project by offering to do the work for Rs10.05 billion, nearly Rs6 billion less than the price quoted by the government.

The Chinese company has used a tunnel boring machine to cut the hills, making Sunkoshi Marin the second project after the Bheri-Babai Diversion Multipurpose Project in Surkhet to do so.

The 12.2-km Bheri Babai tunnel was also built by the China Overseas Engineering Company to irrigate 51,000 hectares of land in Banke and Bardia districts in southwestern Nepal.

The water from the Sunkoshi will first be diverted to the Marin River in Sindhuli through the 7-metre-wide tunnel before being channelled into the Bagmati River. The water will then be collected at a barrage and distributed to irrigated fields.

Low water flows in the Bagmati River have caused severe difficulties for farmers, particularly in Rautahat and Sarlahi districts to irrigate their fields. Irrigation is not available in the dry season.

The Sunkoshi Marin Diversion Multipurpose Project intends to provide round-the-year irrigation to five drought-prone districts in the southern plains, decades after it was envisioned.

The project was first mooted in 2016 when the government had planned to launch a scheme entitled Prosperous Tarai-Madhes Irrigation Special Programme to provide water to parched farmlands in the five Tarai districts.

Insufficient rainfall has long been a recurrent problem in the Madhesh province. A massive outflow of youths to foreign lands, creating a shortage of labourers to carry out agricultural activities, have added to the difficulties of local farmers.

The proposed multipurpose project will inundate 312 hectares of land and create a pond in Sunkoshi and Khadadevi rural municipalities and Manthali Municipality affecting 3,026 households, as per a draft of the environmental impact assessment.

The scheme will also submerge a 1-km stretch of the Banepa-Bardibas Highway (BP Highway) and a 475-metre stretch of the road will have to be relocated to accommodate water intake and other structures.

According to the environmental impact assessment of the Sunkoshi Marin diversion multipurpose project, year-round irrigation will be a boon to farmers as it will help boost production at a time the country is facing a food deficit.

This fiscal year, despite the El Niño phenomenon, Nepali farmers harvested a record 5.72 million tonnes of paddy.

Paddy is transplanted across most of Nepal in June and harvested in October-November.

Paddy is Nepal’s biggest earning farm commodity, with tens of thousands of farmers relying on its income. The high output, according to economists, may cool down inflation and pump up the economy.

The country has 1.43 million hectares of land suitable for growing paddy, with the largest portion (375,340 hectares) in the Madhesh province. However, productivity in Madhesh is one of the lowest among all seven provinces.

According to the statistics at the agriculture ministry, Koshi province surpassed Madhesh province in terms of paddy production this fiscal year, as some districts in Madhesh were hit by drought. Paddy production in Madhesh province dropped to 1.33 million tonnes, down by 3.68 percent year-on-year.