Stretching for 25.2 kilometers (15.7 mi), it bisects the Philippine capital of Manila and its surrounding urban area into northern and southern halves.

During the dry season, the water level in Laguna de Bay is low with the river's flow direction dependent on the tides.

Due to negligence and industrial development, the river suffered a rapid decline in the second half of the 20th century and was declared biologically dead in 1990.

Rehabilitation efforts are also aided by private sector organizations through raising funds or assisting river cleanups.

The San Juan River drains the plateau on which Quezon City stands; its major tributary is Diliman Creek.

The growth of Manila along the banks of the Pasig River has made it a focal point for development and historical events.

In Makati, along the southern bank of Pasig, are Circuit Makati (the former Santa Ana Race Track), the Poblacion sewage treatment plant and pumping station of Manila Water, and the Rockwell Center, a high-end office and commercial area containing the Power Plant Mall.

In El Filibusterismo, the legend tells a story of a rich Chinese man who did not believe in Catholicism that boasted of not being afraid of crocodiles.

[citation needed] Other rock formations in the country that resemble crocodiles can be found near Boracay, and Santa Ana, Cagayan.

The Manggahan Floodway is an artificially constructed waterway that aims to reduce the flooding in the Marikina Valley during the rainy season, by bringing excess water to Laguna de Bay.

Toward the end of the summer or dry season (April and May), the water level in Laguna de Bay reaches to a minimum of 10.5 meters (34 ft).

The Manggahan Floodway was constructed to divert excess floodwater from the Marikina River into Laguna de Bay, which serves as a temporary reservoir.

It was discovered during construction of the Church of the Jesuits in 1921 and was partially damaged during excavation,[13] and was noted to be 'primitive' through a loss of Neanderthal characters and mandibular traits (most notably in the teeth and lack of chin), coining the name Homo manillensis.

The specimen remains undated (although a Quaternary age has been suggested[14]), and Romeo (1979) somewhat equates the skull with Homo sapiens in his description.

[15][16][17] The Pasig River served as an important means of transport; it was Manila's lifeline and center of economic activity.

When the Spanish established Manila as the capital of their colonial properties in the Far East, they built the walled city of Intramuros on the southern bank of the Pasig River near its mouth.

After World War II, massive population growth, infrastructure construction, and the dispersal of economic activities to Manila's suburbs left the river neglected.

[18] In the 1930s, observers noticed the increasing pollution of the river, as fish migration from Laguna de Bay diminished.

Increasing poverty in the rural areas in Philippines has driven migration to Metro Manila in search of better opportunities.

This resulted in rapid urban growth, congestion and overcrowding of land and along the riverbanks, making the river and its tributaries a dumping ground for informal settlers living there.

About 30–35 percent of the river pollution is generated from industries locating close to the river (such as tanneries, textile mills, food processing plants, distilleries, and chemical and metal plants), some of which do not have water treatment facilities which are capable of removing heavy metal pollutants.

The Pasig River Rehabilitation Program (PRRP) was established, with the Department of Environment and Natural Resources (DENR) as the main agency with the coordination of the Danish International Development Assistance (DANIDA).

54 establishing the Pasig River Rehabilitation Commission (PRRC) to replace the old PRRP with additional expanded powers such as managing of wastes and resettling of squatters.

On January 17, 2024, the Bongbong Marcos administration inaugurated its Pasig Bigyang Buhay Muli (PBBM; lit.

Aside from preying on small fish and contributing to the river's murkiness, its population has exponentially risen due to lack of natural predators.