MARIIS Dam and Reservoir Division - Ramon, Isabela


The construction of the Magat Dam and appurtenant structures was authorized by P.D. 693 signed on May 7, 1975 by the late President Ferdinand E. Marcos. The Dam was constructed in 1978 and was inaugurated by President Marcos on October 27, 1982. It started operations in 1983. The project was implemented 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 damsite 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. The dam is part of the Magat River Multipurpose Project (MRMP) which aimed to improve the existing Magat River Irrigation System (MARIS) and the Siffu River Irrigation System (SIFFRIS) and increase the production of rice in the Cagayan River basin.

Fund Source

The project was jointly financed by the Philippine Government and the World Bank which extended a US $50M loan to finance the foreign exchange requirement. In addition, a US $9M from Bahrain was obtained for the purchase of other equipment for the diversion tunnels, soils laboratory and model testing. Total project cost is 3.4B pesos (yr. 1975). The irrigation facilities, including the reservoir, the intake gates to the hydroelectric plant, and the dam itself, is owned and managed by the National Irrigation Administration (NIA) while the hydroelectric plant was owned by the National Power Corporation (Napocor). Under the Electric Power Industry Reforms Act of 2001 (Republic Act No. 9136), the Magat Dam hydroelectric plant underwent a privatization process. As a result, the plant's ownership and operation was turned over to SN Aboitiz Power Inc. (SNAP), a joint venture of a local company, Aboitiz Equity Venture (AEV), and the Norwegian SN Power Invest (SN Power) in April 2007. 


Dam Features

Location: Alfonso Lista, Ifugao / Ramon, Isabela
Construction Begun: 1978
Completion: 1982
Reservoir Area at SFL: 45 sq km
Crest Elevation, MSL: 200 m
Maximum Water Surface [MWS-Flood], MSL: 197 m
Full Supply Level, [MSL]: 193 m
Maximum Supply Level, [MSL]: 160 m
Installed Capacity:    360 MW
Reserved Capacity:    180 MW
Total at FSL [193 m, without sedimentation]:   1.25 BCM
Total at FSL [160 m, without sedimentation]: 317 BCM
Live Storage [193 m - 260 m] without Sedimentation:    1.25 BCM
After 50 years Operation:   832 MCM
At FSL [193 m]:    45 km sq.
At MSL [160 m]:   15 km sq.
Total Crest Lenghts-Embankment Dams and Dikes Including Headworks Structures:   4, 160 m