Water quality management of Laguna de Bay
1991
Santos-Borja, A.C. (Laguna Lake Development Authority, Manila (Philippines))
Laguna de Bay is considered as the largest lake in Southeast Asia having a surface area of 900 km2 and a shore-line of 220 km. The average depth is 2.8 m, with a total volume of 3.2 billion m cubic. Because of its high surface area to volume ratio, the lake is generally turbid during most parts of the year. The only outlet of the lake is the Napindan River which diverges into the Marikina River and the Pasig River. The latter serves as the link between Laguna de Bay and Manila Bay. Backflow of the Pasig River occurs whenever the lake level is lower than Manila Bay. This unique hydraulic regime has serious effects on the lake's water quality aside from the pollution problems emanating from the multiplicity of use of the lake resource. In 1989, a policy decision to utilize the lake for domestic water supply was formulated through a consensus among the different national and regional agencies and some private sector groups. This would require stringent measures to meet the necessary water quality standard. At present, the lake is still classified as a class C water resource which means it is suitable for fishery. Generally, the water quality meets the set standards except in areas within the vicinity of the mouths of polluted rivers. The agency mandated by law to develop the Laguna Lake Region, is the Laguna Lake Development Authority (LLDA). It was also given powers and functions to regulate and monitor activities in the Laguna de Bay region as well as to adopt, prescribe and promulgate the necessary rules and regulations needed in carrying out its mandate. In view of the recent develoments concerning the use of the lake, the LLDA has, as a matter of policy, decided to view lake management through the more responsive watershed or ecosystem approach. The strategic plans for the region include not only the upgrading of the lake's water quality and the conservation of its quantity for water supply, but also on providing alternative means of income to the affected sectors
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