Construction of the dam began in 1975 and ended in 1982 Magat Dam is one of the largest dam in the Philippines and has two primary purposes: as a source of irrigation water and as a provider of hydroelectric power.
The construction and appurtenant structures authorized by PD 693 signed on May 7, 1975 by the late President Ferdinand E. Marcos. The Magat Dam was built in 1978 and inaugurated by Late Pres. Ferdinand E. Marcos on October 27, 1982 and began operations in 1983.
Multipurpose project implementation is based on the preliminary study conducted in 1973 by the National Irrigation Administration (NIA) with the help of the United States Bureau of Recovery (USBR) and United States Agency for International Development (USAID).
The subsequent detailed and extensive study dam site investigation and engineering further confirmed the feasibility of what is now known as the most daring infrastructure projects NIA and one of Asia's largest Dam today.
It is the largest multipurpose dam in South East Asia's. The dam is part of the Magat River Multipurpose Project (MRMP) in which it is financed by the World Bank and that the aim is to improve the existing Magat River Irrigation System (MARIS) and to triple the production of rice in the Cagayan River basin .