The Marikina River is a river in eastern Metro Manila, Philippines. It is the largest tributary of the Pasig River, with headwaters located in the Sierra Madre Mountains in Rodriguez, Rizal province. The Marikina River used to be an important transport route during the Spanish colonial era, but its importance as a transport route diminished when the Philippines' nati…The Marikina River is a river in eastern Metro Manila, Philippines. It is the largest tributary of the Pasig River, with headwaters located in the Sierra Madre Mountains in Rodriguez, Rizal province. The Marikina River used to be an important transport route during the Spanish colonial era, but its importance as a transport route diminished when the Philippines' national highway system became more established. The resulting lack of river boat traffic and the deforestation of the upland areas in what is now the Upper Marikina River Basin Protected Landscape contributed to the river's siltation, further reducing its value as a transport route.