The Royal Irrigation Department (RID) is pushing for an 80-billion-baht project to divert water from the Yuam River in Mae Hong Son through a water tunnel to Bhumibol dam in Tak province.
The proposed project is aimed at addressing water shortages in the Central Plains during the dry season.
Chalermkiat Khongwichianwat, the RID's deputy director-general, said that the project has already undergone an environmental impact assessment study.
A survey and project design study is now under way and is expected to be completed in September or October of next year, he said.
The project will then be submitted to the National Committee on Water Resources and the cabinet for consideration.
If approved, construction is expected to take seven years and it should be completed in 2026, Mr Chalermkiat said. The cost of the project is estimated to be about 80 billion baht, he said.
Under the plan, the water diversion project requires construction of a Yuam River dam, a water pumping station, a water tank and a tunnel which forms a crucial element of the project, he said.
The 61.52km-water tunnel will be dug through a mountain, he said.
During the rainy season, the Yuam River in Mae Hong Son's Sop Moei district has an abundance of water which should be tapped rather than letting it flow wastefully out of the country, he said
In light of this, the plan is to divert the excess of the Yuam River through Chiang Mai where the water will then be sent via the tunnel to the reservoir of Bhumibol dam in Tak province, Mr Chalermkiat said.
The project will feed about 1.79 billion cubic metres (cu/m) of water a year into the Bhumibol dam, he added.
The excess will then be flushed into the Chao Phraya River for farmers in the lower Central Plains Region to use during the dry season when shortages are a problem.
The project will also benefit residents in Bangkok and surrounding provinces as there will be enough water supplies to produce tap water for consumption as well as to generate electricity, Mr Chalermkiat said.
Currently, demand for usable water demand in the Bhumibol dam is 9.66 billion cu/m, but the dam holds only 5.62 billion cu/m. Another 4.036 billion cu/m is still needed to replenish the reservoir, he said.