Lake Lanao Watershed

OIC, Regional Director, DENR ARMM
and concurrent Regional Project
Director, INREMP

      Lake Lanao is located in the province of Lanao del Sur of the Autonomous Region of Muslim Mindanao (ARMM). It is a proclaimed watershed reserve by virtue of Proclamation No.871 issued on February 26, 1992 and is included in the initial components of the National Protected Areas System (NIPAS) governed under NIPAS Act of 1992 (Republic Act No. 7586). ARMM was created in August 1, 1989 by virtue of Republic Act No. 6734 or known as the Organic Act of Autonomous Region of Muslim Mindanao. The province is located south of Lanao del Norte province. On the east is Bukidnon province, and on the south, the provinces of Maguindanao and North Cotabato. To the southwest is Illana Bay, part of the Moro Gulf.

      Lake Lanao is the largest lake in Mindanao, the second largest in the Philippines and is considered as one of the 15 ancient lakes in the world. It has five watersheds with rivers and major tributaries totaling 431 km. The waters from these rivers and tributaries drain into the lake and goes out through only one outlet, the Agus River in Lanao del Norte that flows southwest into Iligan Bay via two channels; Maria Cristina Falls, the largest waterfall in the country and Linamon Falls. The total area of its inland water is 336 ha. Lake Lanao has a surface area of about 36,300 ha.

      A hydroelectric plant installed along Lanao Lake and Agus River generates 70% of the electricity used by the people of Mindanao. Agus River supports seven (7) hydroelectric power plants of the National Power Corporation (NPC) with a combined capacity of 727 megawatts.

      Among the issues and concerns in this river basin are: a) changes in climatological conditions as manifested by i) rainfall irregularity, intensity and erosivity; and ii) reduction in annual rainfall and rainy days; b) land degradation attributed to: i) slope and terrain of watershed; ii) dislocation of timberlands in flatlands and A & D lands in slopes above 18%; iii) deforestation; iv) agricultural activities encroachment into fragile ecosystems; and iv) sand and gravel quarrying that is encroaching critical zones; and c) water utilization as exhibited by: i) lake has lot of water for electric generation while most localities in the lake area do not have water for drinking or irrigation; ii) most agricultural areas are rainfed; iii) serious siltation of the littoral zones of Lake Lanao; iv) overdrawing of water from the lake; and v) un-utilized aquifer in Lumba-a Bayabo.

      Lake Lanao, with an area of 36,274 ha, is the second largest lake in the Philippines. Its water comes from five (5) watersheds around it. These are Taraka-Gata with an area of about 548 km2 or 39% of the basin area, Malaig with 354 km2 (25%), Bubong with 195 km2 (14%), West with 175 km2 (12%) and Saguiaran-Marawi with 141 km2 (10%) for a total river basin area of 1,413.39 km2. Its outlet, Agus River, with a total length of 36.5 km, cuts across the municipalities of Saguiran, Pantar and Baloi and drains into Iligan Bay. The river basin covers 27 municipalities and city and 731 barangays.

      The total population of the watershed is estimated at 720,649 or an average density of 510 persons per km2. There is no estimate of poverty incidence in the river basin. However, for Lanao del Sur, the poverty incidence in 2006 is 58.5%31. It is the most populated INREMP site though only third in terms of land area. Clustering of settlements is most discernible around the lake.

      Although only 21% of the area is cultivated and planted to annual crops, agriculture remains the primary source of livelihood of the people. Rice, corn, coconut, root crops and vegetables are cultivated but the agricultural production is not sufficient to meet the need of the province. This is due to inadequate irrigation, inefficient farming methods, poor agricultural facilities and post-harvest facilities. Other sources of income include handicrafts and timber harvesting activities.

      The Maranaos and External Relations. The indigenous peoples in the river basin are the Maranaos, with pockets of Higaonon, Kolibugan and Iranon. Together, they constitute about 91% of the population of the province of Lanao del Sur. To many Filipinos, Mindanao is noted for its Muslim secessionist movements and the so-called Mindanao problem. But unknown to many, inter-marriage has found its way among the two major groups in Mindanao which had a long history of prejudice and conflict - the Muslims and the Christians.

      The Maranao has to contend with layers of identity: tribal culture with attendant parochial characteristics; identification with Bangsamoroness and struggle for self-determination; passport affiliation as part of being Filipino;and part of the global Ummah. Any of these identities can clash manifested in dilemmas such as: to use taritib or court system when dealing with murder or rido; choosing to get married to mestizo or pure-bred Maranao. Solutions are being provided in part on, "Towards a Culture of Peace." Ongoing initiatives are directed towards: a culture of dialogue that fosters interfaith and inter-tribal communications; a culture of life that denounces killing as if one kills the whole of humanity; and Tawheed, or submission to the will of Allah.

Bubong 195.46 13.83 Bubong
Ditsaan Ramain
Marawi City
Malaig 354.03 25.05 Bayang
S. Dumalondong
Taraka Gata 547.89 38.76 Lumba-Bayabao
Poona Bayabao
Saguiran-Marawi 141.05 9.98 Saguiran
Marawi City
West 174.96 12.38 Bacolod Grande
TOTAL 1,413.39 100.00 34 / 27* 731

*Counting of covered municipalities avoided double counts.

      Climate and Rainfall. The basin area falls under the 4th climatic type (Corona's Classification) where there are no pronounced dry or wet seasons. The area is outside the typhoon belt. The average annual rainfall is about 2,440 mm. The highest recorded annual rainfall is 5,235 mm at Lumba-Bayabo station in 1992.

      Topography and Slope. The elevation of the river basin ranges from 700 m at Lake Lanao to 2,600 masl in the municipalities of Lumba-Bayabao. An estimated 62% of the total area have slopes of 0-18% (flat to rolling), 22% have 18-30% slope (steep) and 16% have over 30% slope (very steep to critical slope). Of the areas classified as forest lands, 54% have slopes of 0-18%, while 46% have slopes of 18% or higher. For A & D lands, 83% have 0-18% slope while 17% have slopes over 18%. Of the total cultivated area planted to annual crops and perennial crops, only 4% are in areas with slopes of greater than 30%.

      Forest and Vegetation Types. Out of the 141,000 ha of basin area, 102,088 ha or 72% have been classified as forestland, while 39,251 ha or 28% are A&D lands. Of the 102,088 ha of forest land, 78,826 ha or 77% are with forest cover, while the remaining 23% are distributed among other land uses such as built-up area, annual and perennial crops, shrubs and grasslands.

      On the other hand, of the 39,251 ha of A&D lands, 2,186 ha or 6% are with forest cover, 37,065 ha or 94% are currently under other land uses, most of which are cultivated and planted to annual or perennial crops, and the rest are shrubs, grassland, wooded grassland or built-up areas. About 81,012 ha or 58% of the basin have forest cover, of which 97% are legally classified forest lands and 3% are A&D lands. The forest cover is composed of 46,220 ha or 57% closed canopy forest, 34,792 ha or 43% open canopy forest.

      Based on the Lake Lanao Integrated Development Plan, there exist about 40,000 ha of old growth dipterocarp forests, 35,000 ha of residual dipterocarp forests, 5,500 ha of submarginal forests and 2,200 ha of mossy forests in the watersheds. There are also some 1,300 ha of residual dipterocarp forests within A&D areas. The old growth dipterocarp forest is composed of 44% common hardwoods, 40% construction and furniture wood, and 16% other species. Among the common hardwoods are Almon (Shorea almon), Bagtikan (Parashorea plicata) Kalunti (Shorea kalunti), Mayapis (Shorea squamata), Nato (Palaqium luzoniensis), Red lauan (Shorea negrosensis), Tanguile (Shorea philippinensis) and White lauan (Pentacme contorta). The furniture and construction wood species are Apitong (Dipterocarpus grandiflorus), Bangkal (Antocephalus cadamba), Batikuling (Litsea leytensis), Bolong-eta (Diospyrus pilosanthera), Dalingdingan (Hopea foxworthii), Ipil (Instia bijuga), Kalumpit (Terminalia microcarpa), Kamagong (Diospyrus philippinensis) and Katmon (Dillenia philippinensis).

      Biodiversity Assets. Lake Lanao Watershed is an important biodiversity site in the Philippines that is of global significance and is therefore one of the priority sites for conservation (KBA 109). The lake is home to 18 endemic species of freshwater fish and supports a large number of waterfowls. Among other species, the lake is home to the native cyprinids consisting of 20 species of the genus Barbodes and several genera – Mandibularca, Spratellicypris, Cepahlokompsus and Capatulus. These species are accordingly under threat by the introduction of predatory marine species such as white goby. Though the watershed does not have a good baseline data for biodiversity, it was reported that in two barangays that were surveyed during the preparation of the Integrated Development Plan of the Watershed, 27 species of trees, shrubs, and vines were observed while 41 medicinal plant species were recorded. Likewise, available information also shows that there are six (6) bird species in the watershed. Among them are the Halikyon chloris (white collared kingfisher), Corvus enea (slender bird crow), and the Dubulens ibis coromandus (cattle egret).

      Mineral Resources. Metallic minerals are mostly found along the boundary of the watershed with Lanao del Norte and North Cotabato. These include copper, gold, chromium, manganese and silver. Non-metallic minerals are found in the North-eastern side of the watershed. These are clay, gypsum, phosphate, bentonite sand, gravel and feldspar.

      Entry to the province is via the concrete paved national highway from Cotabato City or Iligan City. All municipalities within the province are accessible during all weather condition by any means of land transportation. Within the river basin, the national road is about 122 kilometers, majority of which is the Lake Lanao circumferential road connecting all the lakeshore municipalities. Provincial road within the basin is about 374 km and municipal road is 344 km. Of these total road length, 71 km are paved, 290 km gravel and 479 km are classified as earth road.

      The potential irrigable area within the basin is 15,116 ha with 9,300 classified as national scheme and 5,816 ha as communal. Irrigated area within the basin to date is about 6,320 ha equivalent to a development rate of 41.8%. Of these existing area, the 3,000 ha under Rugnan RIS and 1,200 under Masiu IS are undergoing rehabilitation works under the ADB funded SPISP and CARP-IC, respectively, while about 1,963 ha of the existing communal scheme is proposed for rehabilitation and improvement.

      There is no disaggregated distribution of access to potable water supply by municipality but the provincial figure shows that 68% of the total households have access to potable water supply. The residents in barangays drawing potable water from Lake Lanao declare that these sources are safe but looking at the health statistics of the province, the top two causes of morbidity is diarrhea and skin diseases.