Magat Dam is a large rock-fill dam in the island of Luzon in the Philippines. The dam is located along the Magat River, a major tributary of Cagayan River. The construction of the dam started in 1975 and was completed in 1982. It is one of the largest dams in the Philippines. It is a multi-purpose dam which is used primarily for irrigating about 85,000 hectares (210,000 acres) of agricultural lands,[1] flood control, and power generation through the Magat Hydroelectric Power Plant.

Magat Dam
Magat dam and sign.JPG
The dam, with its entrance sign in the foreground
Magat Dam is located in Luzon
Magat Dam
Location of Magat Dam in Luzon
Magat Dam is located in Philippines
Magat Dam
Magat Dam (Philippines)
LocationAlfonso Lista, Ifugao / Ramon, Isabela
Coordinates16°49′30″N 121°27′14″E / 16.82500°N 121.45389°E / 16.82500; 121.45389Coordinates: 16°49′30″N 121°27′14″E / 16.82500°N 121.45389°E / 16.82500; 121.45389
Construction began1978
Opening date1982
Dam and spillways
Type of damRock-fill dam
ImpoundsMagat River
Height114 m (374 ft)
Length4,160 m (13,650 ft)
Surface area11.7 km2 (4.5 sq mi)
Maximum water depth193 m (633 ft)
Power Station
Installed capacity360 MW

The water stored in the reservoir is enough to supply about two months of normal energy requirements.[1]


The construction and appurtenant structures was authorized by Presidential Decree No/ 693 signed on May 7, 1975 by then President Ferdinand E. Marcos. The Magat Dam was constructed in 1978 and inaugurated by Marcos on October 27, 1982[1] and started operations in 1983.[2]

Implementation of this multipurpose project was based on the preliminary study conducted in 1973 by the National Irrigation Administration (NIA) with the assistance of the United States Bureau of Reclamation (USBR) and the United States Agency for International Development (USAID).

Subsequent detailed and extensive dam site investigation and engineering studies further confirmed the feasibility of what is now known as NIA's most daring infrastructure project and one of Asia's biggest dams today.

It was Southeast Asia's first large multipurpose dam.[3] The dam is part of the Magat River Multipurpose Project (MRMP) which was financed by the World Bank and whose purpose is to improve on the existing Magat River Irrigation System (MARIS) and to triple the production of rice in the Cagayan River basin.[1]

The project was jointly financed by the Philippine Government and the World Bank which extended a US$150M loan to finance the foreign exchange requirement. In addition, a US$9M loan from Bahrain was obtained for the purchase of other equipment for the diversion tunnel, soil laboratory and model testing. The total project cost is US$3.4B (yr. 1975).

The dam was constructed to last for 50 years but increased siltation and sedimentation in the reservoir, slash-and-burn farming, illegal logging and fish-caging resulted in the deterioration of the dam's watershed. The 1990 Luzon earthquake also contributed to the increased siltation in the Magat River system. Because of this, on January 2006, then President Gloria Macapagal Arroyo instructed various government agencies to create a rehabilitation plan to improve the lifespan of the dam system.[3]

The non-power components such as the dam, reservoir, and intake gates are owned, operated, and managed by the National Irrigation Administration (NIA). The hydroelectric plant was formerly owned by the National Power Corporation (NAPOCOR).[1] Under the Electric Power Industry Reform Act of 2001 (Republic Act No. 9136), the Magat hydroelectric power plant underwent a privatization process. As a result, the plant's ownership and operation was turned over to SN Aboitiz Power-Magat, Inc. (SNAP-Magat), a joint venture of a local company, Aboitiz Power Corporation (AP), and a Norwegian firm SN Power in April 2007.[1] SNAP won the bidding in 2006.[4]


The dam is located within the boundaries of Namillangan, Alfonso Lista, Ifugao and Ramon, Isabela, approximately 350 kilometres (220 mi) north of Metro Manila.

Magat RiverEdit

The Magat Dam is on the Magat River, which is the largest tributary of the Cagayan River on the island of Luzon.[5] Cagayan is the longest river in the Philippines.[5] The Magat River has an estimated yearly water discharge of 9,808 million cubic metres and has an approximate crest length of 4,160 metres (13,650 ft) with its headwaters in the province of Nueva Vizcaya and its confluence with the Cagayan River in the province of Isabela.


The Magat power plant, located at the base of the dam.


  • Length: 500 metres (1,600 ft)
  • Width: 164 metres (538 ft)
  • Discharge capacity: 30,600 cubic meters
  • Radial Gates: 7 sets
  • Orifice Gates: 2 sets

Diversion tunnelsEdit

  • Number: 2
  • Diameter: 2 metres (6.6 ft)
  • Average length: 630 metres (2,070 ft)


  • Storage Capacity at Full Supply Level (FSL): 1.08 billion cubic meters[6]
  • Elevation at FSL: 193 masl[6]
  • Minimum Supply Level: 160 masl[6]
  • Maximum Flood Level: 193 masl[6]


  • Installed capacity: 360 MegaWatts
  • Turbine: 4 units, Francis vertical shaft
  • Generator: 4 units x 90 MW, vertical synchronous


It is connected by an all-weather road to San Mateo–Santiago Road at Oscariz, Ramon, Isabela some 350 kilometres (220 mi) north of Metro Manila.

Magat HydroEdit

The Magat hydroelectric power plant is a four-unit powerhouse with an installed capacity of 360 megawatts.[1] It is designed to accommodate two more units[7] that will allow it to generate up to 540 megawatts. The hydroelectric plant is a peaking power plant,[1] which means that it only operates when there is a high demand for electricity in the Luzon power grid, to which the plant is connected.[8] It is capable of providing ancillary services for the stability of the grid.

SN Aboitiz Power-Magat, Inc. completed the half-life refurbishment of the Magat Hydroelectric Power Plant in 2014. Refurbishment began in 2009 and was completed in June 2014.[9] Half-life refurbishment ensures that the power plant facility remains available throughout its life span.

Discharge-induced floodsEdit

In November 2020, Typhoon Vamco (locally known in the Philippines as Typhoon Ulysses) crossed the country, dams from all around Luzon neared their spilling points, forcing them to release large amounts of water into their impounds including Magat Dam. The dam opened all of its 7 gates at 24 meters, releasing over 5,037 cubic metres (1,331,000 US gal) of water into the Cagayan River resulting to numerous riverside towns experienced massive flooding. Waters under the Buntun Bridge went up as high as 13 meters, flooding the nearby barangays up to the roofs of houses.,[10][11] Prior to the flooding, The National Irrigation Administration said Sunday it had already warned residents of Cagayan and Isabela of Magat Dam's water release two days prior Typhoon Ulysses' landfall on November 11.[12] As a result of the catastrophe, the National Irrigation Administration said that it will review its protocols regarding the release of water in Magat Dam and improve its watershed.[13]


  1. ^ a b c d e f g h "Magat Hydro: Environmental & Social Review Summary" – International Finance Corporation (World Bank)
  2. ^ "Magat Hydro". Retrieved January 14, 2016.
  3. ^ a b "Arroyo orders officials to formulate plan for massive rehabilitation of Magat Dam". Manila Bulletin. January 6, 2006. Retrieved April 21, 2008.
  4. ^ "Ifugao, Isabela share natl wealth tax over Magat dam after legal battle". GMANews.TV. GMA Network. April 4, 2008. Retrieved April 21, 2008.
  5. ^ a b "The Cagayan River Basin" – PAGASA. Accessed on April 21, 2008.
  6. ^ a b c d "Magat". Retrieved January 14, 2016.
  7. ^ "Phillippines [sic] – SNPower". Retrieved January 14, 2016.
  8. ^ Visaya, Villamor Jr. (July 29, 2007). "Gov't starts cloud-seeding over Magat dam". Philippine Daily Inquirer.
  9. ^ "Magat". Retrieved January 14, 2016.
  10. ^ "Robredo assures Cagayan Valley: We heard you, gov't finding ways to reach you". November 13, 2020.
  11. ^ "Cagayan province turned into 'Pacific Ocean': Disaster management official". November 13, 2020.
  12. ^ "Residents near Ipo, Ambuklao, Binga, and Magat dams warned of flooding as reservoirs continue to release water".
  13. ^ "NIA to review protocols on Magat Dam water release after Cagayan, Isabela floods".