Manila Bay is the premier international gateway to the country’s political, economic and social center. The Bay has been known for its strategic importance ever since the pre-colonial times. One of the finest natural harbors in the world, Manila Bay was a focal point of the manila-Acapulco Galleon Trade. The Bay has been a scene of many battles, and until today a historic naval base in Cavite stands, guarding the entrance to the Bay.

The manila Bay area is a place of many striking contrasts. Monuments and sculptured images of heroes past stand amidst glass, steel and concrete skycrapers. Centuries-old churches are a stone’s throw away from big shopping malls and posh hotels. The walled city of Intramuros- the bastion of Spanish rule, Corregidor’s ruined barracks and artilleries- testimony of heroism in World War II, ancestral houses, museums and historical markers take one down along memory lane. Theater and open-air performances offer a cultural interlude.

The surface area of the Bay is about 1,800km2 and the surrounding watershed area of 17,000 km2. The 190 km coastline is intersected by the (7) major rivers, draining 26 catchment basin. These rivers are the major sources of marine pollution in the Bay. The Bay 60 km long, may be entered through a channel 18 km wide, in which Corregidor and Caballo Islanda are situated. It is bordered by  coastal cities and municipalities of the National Capital Region or NCR ( Manila Pasay, Paranaque, Las Pinas, and Navotas), and the coastal provinces of Bataan, Pampanga, Bulacan in Region 3 =, and Cavite in Region 4. Also within the watershed of Manila Bay are non-coastal cities and municipalities of the NCR (Quezon City, Caloocan City, Makati, Pasig, Marikina, Mandaluyong, Muntinlupa, Valenzuela, Malabon, San Juan, Pateros, and Taguig), provinces of Nueva Ecija and Tarlac Region 3, and Rizal and Laguna in Region 4.

the two main contributory areas are the pasig and the pampanga river basins. the pasig river connects manila bay with laguna de bay, largest freshwater lake in southeast asia. most of the river system in the province of pampanga, bulacan and nueva ecija drain into the pampanga river (bfar, 1995). other major rivers discharging directly into manila bay are talisay, pasag, meycauayan, navotas-malabon-tullahan-tenejros, and maragondon. freshwater inflow has been estimated at approximately 25 cubic kilometers/year. seasonal and annual variations in discharges are pronounced with the largest input occurring in august and the lowest in april. the typical retention time for freshwater in the bay is between two weeks and one month, depending on the season (prrp, 1999).