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 , President Gloria Macapagal-Arroyo instructed various government agencies to create a rehabilitation plan to improve the lifespan of the dam system
1990 Luzon earthquake
1990 Luzon earthquake
Magat Dam