The Control of Saltwater Intrusion into Laguna de Bay: Socioeconomic and Ecological Significance

ABSTRACT

Laguna de Bay is the largest lake in Southeast Asia. At present it is being used for fishery, irrigation, power generation, and navigation and is considered to be a source of potable water in the year 2000. The only outlet of the lake is the 24 km Pasig River which drains into Manila Bay. When the lake level is lower than Manila Bay, the Pasig River enters the lake via the Napindan Channel. However, the water is not only saline, but also deoxygenated and polluted with industrial and domestic effluents. The backflow of the Pasig River further aggravates die pollution problem in the lake.

In 1983 a hydraulic control structure (HCS) was constructed at the confluence of the Pasig-Napindan River in order to prevent further pollution of the lake and to control the storage of lake water to firm up a dependable outflow for water supply and irrigation. However, operation of the HCS became a controversial issue among the different lake users. Fishermen and fishpen operators are against its operation because they claim it would reduce the natural food supply of fish especially the cultured milkfish. On the other hand, other sectors claim that the HCS is beneficial because it prepares the lake for its intended and future uses. Operation of the HCS continues to be a debatable issue and, due to pressures from different sectors, the HCS remains open from 1985 up to the present.

Key Words:

• Pasig River
• saline water pollution
• milkfish