Pasak Jolasid Dam

         Pasak Jolasid Dam is a royal initiative by His Majesty King Bhumibol Adulyadej to mitigate flood and store water. Pasak Jolasid Dam is the biggest earth dam in Thailand. His Majesty the King granted a royal permission to name the dam “Pasak Jolasid” and graciously performed the opening ceremony on November 25, 1999.



         “Pasak River is one of the most important rivers in Lop Buri and Saraburi Provinces. The river benefits agriculture and fishery significantly.

         In the past, from August to October every year, there were sudden floods in many areas of Lop Buri, Saraburi, Ayutthaya, and Bangkok Provinces. From January to May, Pasak River Basin was dry and lacked water for agricultural purpose and household consumption.

         In 1965, Royal Irrigation Department started conducting a feasibility study of Pasak River Project before it was suspended as the cost was high. However, as His Majesty King Bhumibol Adulyadej saw the difficulties of his people when he went to visit the areas, he told the Royal Irrigation Department to further the feasibility study of Pasak River Project to mitigate water shortage and floods.



         Phatthana Nikhom District, Lopburi Province and Wang Muang District, Saraburi Province


Rainwater catchment Area 14,520 square kilometers
Average streamflow (1955-1992) 2,400 million cubic meters/year
Highest overflow 3,900 cubic meters/second


Maximum pool level +43 meters MSL
Normal pool level +42 meters MSL
Storage capacity 785 million cubic meters

Service Spillway

Type steel-reinforced concrete with radial gate
Number of floodgates 7 gates
Floodgate dimensions (width x height) 12.5 x 8 meters
Drainage ability 3,900.00 cubic meters/second

Dam feature

Type earth dam with clay core
Crest elevation +46.5 meters MSL
Length 4,860 meters
Height 31.5 meters


Pasak Jolasid Hydropower Plant

         Pasak Jolasid Hydropower Plant is a coordination on renewable energy between Electricity Generating Authority of Thailand and Royal Irrigation Department. The project aimed to utilize the maximum use of water in the dam in compliance with power strategic plan of the Government announced in September 2003 that supported renewable energy development to reduce the fuel import.

         In December 2003, the Cabinet announced the policy to support the small hydropower power plant construction behind the Royal Irrigation Department’s dams to generate the electricity from the normal water releasing of the dam. Ministry of Agriculture and Cooperatives was assigned to be responsible for the project which was technically supported by Ministry of Energy. Royal Irrigation Department and EGAT were assigned by the 2 ministries to implement the project. EGAT was committed to developing 6 downstream hydropower plants with a total capacity of 78.7 MW that were approved by the Cabinet on December 12, 2006. One of the 6 approved projects was Pasak Jolasid Downstream Hydropower Plant.


Power Plant Building

         The power plant building is 22.50 meters wide, 40.50 meters long, and 38.60 meters high. Inside the power plant building, a 6.70 MW generator was installed. The power that is generated is supplied to the 22 kV transmission line. The power plant can generate electricity of 34.80 million units annually (million kWh).



  1. Reduce the fuel use and environmental impacts
  2. Generate electricity 34 million units/year
  3. Reduce the oil import
  4. Support the research and study on electricity generation from renewable energy
  5. Add the electricity capacity in the national system
  6. Create the local employment during construction
  7. Improve the power system security in Phatthana Nikhom District and neighboring areas.
  8. Promote the dam as tourist attraction


June 2018