The Abra River is the sixth largest river system in the Philippines in terms of watershed size. It has an estimated drainage area of 5,125 square kilometers and a length of 198 kilometers from its source in the vicinity of Mount Data in the Benguet province.
Traversing the provinces of Benguet and Pangasinan, it is the third largest river system in the country with a drainage area of 5,952 km². It originates in the Cordillera Mountains and empties into the South China Sea via the Lingayen Gulf. The river is 206 km long. Roughly 2 million people live in the Agno River Valley and it comprises one of Philippines' larger population clusters. The river is dammed by three hydroelectric power plants; the Ambuklao Dam in Bokod, the Binga Dam in Itogon, and the San Roque Dam in San Manuel.
The Abulog or Abulug is the 9th largest river system in the Philippines in terms of watershed size. It has an estimated drainage area of 3,372 square kilometres (1,302 sq mi) and a length of 175 kilometres (109 mi) from its source in the mountains of Apayao in the Cordillera Administrative Region. More than 90% of the drainage area of the river is located in Apayao province while the remaining, including the mouth of the river, is in Cagayan province. The upper reaches of the Abulug River, especially upstream from Kabugao, is commonly known as the Apayao River.
Bicol River is the eight largest river in the Philippines in terms of drainage basin size with an estimated catchment area of 3,770 km². The river drains the southwestern part of the island of Luzon and passes through Camarines Surprovince in the Bicol Region. The river starts from Lake Bato, 6 metres above sea level, and flows 94 kilometres downstream to its estuarine mouth at San Miguel Bay. The basin has an influence area of 10,058 square kilometres including its drainage basin.
The Buayan-Malungon River Basin is considered as an allied sub-basin of Mindanao river basin. It has an area of approximately 150,509.79 ha. It is located in Southern and Central Regions of Mindanao. In the east, it is bounded by Mt. Matutum in Malungon, and drains to its outlet, the Sarangani Bay. Buayan and Malungon rivers are its main tributaries. Buayan River, which originates from Mt. Matutum at the western side, is the river basin’s main water body. Several rivers particularly within General Santos City, South Cotabato, and Alabel, Sarangani also serve and tributaries to be delivered to Sarangani Bay (DENR Region XII 2007).
The Cagayan River, also known as the Rio Grande de Cagayan, is the longest and 2nd largest river in the Philippine Archipelago. The river's headwaters are at the Caraballo Mountains of the Central Luzon at an elevation of approximately 1,524 metres (5,000 ft). The river flows north for some 354 kilometres (220 mi)to its mouth at the Babuyan Channel near the town of Aparri, Cagayan. The river drops rapidly to 91 metres (299 ft) above sea level some 227 kilometres (141 mi) from the river mouth. Its principal tributaries are the Pinacanauan, Chico, Siffu, Mallig, Magat and Ilagan Rivers.
The Cagayan de Oro River Basin (CDORB) is one of the major river basins of the Philippines with a total area of 1,373.84 km2 in Northern Mindanao. The basin encompasses three provinces in Region X. It is bounded by Northern Cotabato in the south, by Lanao del Sur in the south west and by Bohol Sea in the north. It is the water rafting capital of Mindanao and a home to eight (8) sub-watersheds.
The Central Cebu River Basins cover around 67, 870 ha in ten Local Government Units (LGUs) in the Province of Cebu and covers 214 barangays. Cebu City has the most number of barangays within the river basin with all of its 80 barangays within the basin. Mandaue City exhibits the same case, with all of its 27 barangays located within the river basin. The Municipality of Minglanilla has only two barangays within the river basin.
One of the major river basins in the Philippines is the Davao River Basin (DRB). It has a total area of 1,598 km2. covering the province of Bukidnon and Davao City in Regions X and XI respectively.
The Iloilo River located in the Province of Iloilo, Philippines is actually an estuary. The river starts in Oton at Batiano River, which is also an estuary, then traverses the Iloilo City districts of Lapuz, Lapaz, Mandurriao, Molo, Arevalo and the city proper, before emptying into the Iloilo Strait.
Jalaur River, also known as Jalaud River is the second largest river in island of Panay and the 17th largest river system in the Philippines in terms of drainage basin size.
Marikina River is a river in eastern Metro Manila, Philippines. It is a tributary of Pasig River with headwaters located in the Sierra Madre Mountains in Rodriguez, Rizal province.
The Mindanao River Basin is the second largest river system in the Philippines, and the largest in Mindanao. Located in the Central and a portion of Southern Mindanao, it has a total catchment area of 21,503 km2. It is also the largest bird sanctuary in Mindanao and a habitat of crocodiles. It covers the area from the mountains of Impasug-ong in Bukidnon (known as Upper Pulangi River), Kabacan River (relabeled as Mindanao River), Lower Pulangi River and Ligawasan Marsh. The latter serves as natural flood storages, from which the river system splits to the Tamontaka and Rio Grande de Mindanao Rivers and finally exits to Illana Bay.
Panay River is a river of the Philippines, draining a large portion of Panay Island in Western Visayas region.
The Ranao (Agus) River Basin is bounded on the north by Iligan Bay, Bukidnon province on the east, Maguindanao and North Cotabato provinces on its south and Illana Bay on its southwest. It has a total land area of 1,987.07 km2 consisting of five major subwatersheds which supply water to Lake Lanao. Agus River serves as the drainage of Lake Lanao. Also, it is a hydropower source for Mindanao.
Tagoloan River Basin (TRB) is the 13th largest river system in the Philippines in terms of watershed size, with total drainage area of 1,801.027 km2.Situated in the provinces of Misamis Oriental and Bukidnon, its main drainage way is the Tagoloan River with a generally north western flow. On the other hand, the Macajalar Bay serves as the discharge point of the whole basin.
Tagum-Libuganon River Basin (TLRB) has an area of 2,374 km2 which covers the provinces of Davao del Norte and Agusan del Sur.