River Basins

The Philippines has 412 principal river basins in 119 proclaimed watersheds. Of these, 19 are considered major river basins. The longest river is the Cagayan in Region II. Other important rivers in Luzon include the Agno and Pampanga, crossing the plains of Central Luzon; the Pasig, a commercially important artery flowing through the center of Metro Manila, providing the main drainage outlet for most of the waterways; and the Bicol, the primary river of Region V. the principal river of Mindanao is the Rio Grande de Mindanao, which receives the waters of the Pulangi and the Agusan.

The Pasig River which passes through the center of Metro Manila and serves as its major waterway, has become seriously polluted over time. Through the rehabilitation effort of the Government the Water quality of the Pasig River showed improvement over the last 5 years which include the following:

• Improvement of the DO levels from 1998 to 2001 in nearly all stations;
• Increasing number of stations is passing ambient WQ criteria;
• Improvement of the BOD levels from the 1998 to 2001 in nearly all stations;
• Odor of the river is reduced; and
• BOD load (from domestic sewage, solid waste, and commercial; and industrial liquid wastes) and floating solid wastes have been reduced which shows the importance of solid waste as a source.

Figure 1 : DO Levels in the Pasig River System

Source: DENR-Environment Management Bureau

Figure 2 : BOD Levels in Pasig River System, 1998-2001

Source: DENR-Environment Management Bureau

Source: Philippines Environment Monitor 2003

Related Presentation:Plans and Programmes of River Basin Control Office relative to Water Resources Management