FACTS:The Laguna de Bay Masterplan
LLDA / DENRhttp://www.llda.gov.ph/masterplan.htm
The Laguna de Bay watershed region as a natural resource is strategically situated in the midst of the country’s center of urban and industrial development. Aside from Metro Manila which lies just west of Laguna de Bay, the region straddles the whole of Laguna and Rizal provinces, parts of Batangas, Cavite and Quezon which compose the CALABARZON area. This configuration makes the region a critical resource in terms of its importance as the main source of agricultural food commodities and industrial raw materials. The lake itself as well as the other smaller lakes in the basin are important sources of livelihood for the fishery sector and serve multifarious purpose - in irrigation, transportation, energy generation and other industrial uses.
The geographic features and location of the basin within the primary growth area of the country make it susceptible to destructive human interventions which in the long-term may cause irreparable damage to its resources including the loss of valuable agricultural and forest lands to urban and industrial growth.
A strategic resource of the Region is the Laguna de Bay, the second largest body of freshwater in Southeast Asia. It has a surface area of approximately 90,000 heactares, an average depth of 2.8m, a total volume of 3.2 billion cubic meters measured at elevation 11.50 meters above the Laguna de Bay datum set at 10.0 meters below the Mean Lower Low Water (MLLW)
and a shoreline of 220 kms. There are 21 tributaries that drain into the lake; 35% of freshwater that drains comes from Pagsanjan River while 15% comes from the Sta. Cruz River. The only outlet of the lake is the Napindan Channel which at its confluence with the Marikina River, forms the Pasig River. This river meanders along 24-km. long course westward through a major part of Metropolitan Manila, before finally discharging into Manila Bay.
Laguna de Bay Region boundaries include six (6) provinces, 60 municipalities of which 28 towns are lakeshore and 32 non-lakeshore towns. The actual population of the Region including Metro-Manila was approximately 8.3 Million in 1990 and is expected to rise to 12.0 Million by year 2000. The lake is the singly most important resource of the Region. At present it is a source of industrial cooling water, irrigation water, and hydroelectric power; a transport route for oil products and the lakeshore dwellers; a source of snails for duck feed; a venue for recreation and most notably a source of fish supply. Also, the lake serves as a huge sink for waste coming from domestic sources (household and service sectors); non-point sources (surface run-off from urban areas, crop lans and forest lands); industries, livestock and poultry production, fishery activities and Pasig River and Manggahan Floodway inflow. The latter is most alarming since its pollution and sediment load will jeopardize the existing and potential uses of the water body. LOCATION
Today, Laguna de Bay cover almost one half of the 190,000 ha. total area of all existing lakes in this country. It is known as the second largest inland body of water in Southeast Asia next to Lake Toba in Indonesia (Santos-Borja, 1994). It has a total surface area of about 90,000 has. and an average depth of 2.8 m. Laguna de Bay stands unique in the sense that it is right in the middle of its upper watershed. It lies just east and generally south of Metropolitan Manila. The lake has a total volume of 3.2 billion cubic meters with a shoreline of 220 km. There are 21 tributaries that drain into the lake; 35% of freshwater that drain comes from Pagsanjan River while 15% comes from Sta. Cruz River. The only outlet of the lake is the Napindan Channel which at its confluence with the Marikina river, forms the Pasig river, which meanders along a 24 km. long course westward through a major part of Metropolitan Manila, before eventually discharging into Manila Bay
(Francisco, 1985). Other lakes in the region also include the Seven Crater Lakes in San Pablo City with a total surface area of 289.6 has. and Tadlak Lake in Los Baños with only 22.6 ha. area.
Laguna de Bay Region occupies 1.3% of the total land area of the Philippines. It encompasses the whole provinces of Rizal and Laguna, the cities of San Pablo, Pasay, Caloocan, Quezon, Manila and Tagaytay, the towns of Tanauan, Sto. Tomas and Malvar in Batangas, the towns of Silang and Carmona in Cavite; Lucban in Quezon province and Marikina, Pasig, Taguig, Muntinlupa and Pateros in Metro Manila. To sum it up, Laguna de Bay Region boundaries include 6 provinces, 60 municipalities of which 28 towns are lakeshore covering 177 barangays and 32 non-lakeshore towns.
Laguna de Bay is trilobate lake with three corporate bays: The West Bay, Central Bay and East Bay that converge towards the South carving out what resembles a large bird or dinosaur. The West and Central Bays are separated by Talim Island, the largest and most populated of the nine islands within the lake. It is bordered by the ruggedly high Sierra Madre mountain ranges on the Northeastern portion, the high Caliraya volcanic plateau in the East and the chains of mountains of Laguna and Batangas province to the South and Southeast, which includes Mt. Banahaw and Mt. Makiling. HYDROLOGY OF THE LAKE
The hydrology of the lake has a natural stage regime which in the dry season results in a minimum lake elevation of about 10.5 m. controlled by mean level in Manila Bay.
At the end of the dry season, the lake level may drop below the level of high tide in Manila Bay, resulting in the intrusion of seawater up the Pasig river. With this diurnal reversal, the highly polluted waters of the Pasig river system are carried in the lake. The tidal influx is also the primary cause of elevated salinity in the lake during this part of the year (Francisco, 1985). During the wet season, precipitation results in an annual mean high water elevation of 12.5m. and a peak elevation which may reach as high as 14.6m for a 100 year recurrence interval.
During extremely wet years, widespread flood damage occurs along the lakeshores because the land is relatively flat for several kilometers inland in most areas. Also during this period, the Marikina river floods the Pasig river and overflows into the Laguna de Bay via the Napindan Channel because the Marikina river can generate floodflows of about 200 m3s to 4000 m3s, and because the Pasig river bank full channel capacity varies from as little as 50 m3 to only about 750 m3s.
Depending upon the tide and local inflow, the Marikina river causes flooding in and around Metropolitan Manila.Laguna De Bayhttp://en.wikipedia.org/wiki/Laguna_de_BayLake Calirayahttp://en.wikipedia.org/wiki/Lake_CalirayaPagsanjan Riverhttp://en.wikipedia.org/wiki/Pagsanjan_RiverSta Cruz Riverhttp://en.wikipedia.org/wiki/Sta._Cruz_River