Lake Lanao is a large, oligotrophic freshwater lake, located on Mindanao Island in the Philippines. It is the second largest lake in the country, the largest on the island and is one of the 15 ancient lakes of the Planet.
Geography and Hydrology
Lake Lanao, located in the Southern part of the Philippines in Lanao del Sur province, was formed by the tectonic-volcanic damming of a basin set between two mountain ranges, and the collapse of a large volcano. It is bordered on the south and southeast by extensive forests and the majority of its coastline houses vast reed beds. The lake basin is shallowest on the northern part, but deepens progressively towards the south.
The lake has four main tributaries, but its only outflow is the Agus River, which flows northeast into the Iligan Bay through two channels: one located on the Maria Cristina Falls, and one over the Linamon Falls.
Numerous towns and communities can be found on the lakeshore, such as Marantao, Marawi City, Mulondo and Tamparan, a lot of which are Muslim. The most popular recreational activities are boating, swimming and sport fishing.
Flora and Fauna
The lake is home to many fish and vertebrates and served as an exceptional research site regarding the evolutions of cyprinids, of which 20 endemic species could be found in Lanao in the past. Out of these 20 fish none were found in 2008, according to research studies on Lake Lanao. Specialists affirmed that this unfortunate turn of events was due to a mixture of overfishing, pollution and competition from introduced fish species. According to another study led by Marano State University, the disappearance of these fish was caused by a massive algae contamination, due to poor sewage and agricultural waste management. The Department of Agriculture, together with the Bureau of Fisheries and Aquatic Resources stated that indiscriminate logging, along with extensive land use and farming caused the loss in Lake Lanao’s flora.
Lake Lanao was proclaimed a watershed reservation in 1992 through the Presidential Proclamation, which aims to protect the local forest cover and the water yield for irrigational, domestic use and hydropower. A total of 42 endemic crab species inhabit the lake. The Philippine duck also uses Lake Lanao as a breeding and nesting space.
Legends and Myths
Lake Lanao is home to many myths and legends of the Meranaw tribe. A myth regarding the lake’s formation states that a group of angels under the command of Gabriel removed the vast population of Mantapoli from the area, to prevent the world from tipping over. The hole that was left was filled with water and threatened to drown the rest of the world. In a response to this fact, the angels joined forces with the Four Winds to gauge out and outlet for the lake, and thus Agus River was created.
The Meranaw is the spoken language of the Marano people. It derives from the name of the lake and means “people living around the lake”.
Hydroelectric Power Supply
Between 1953 and 1978 the National Power Corporation has been operating five power plants along the Agus River, using its high-energy water flow. In 1978 they installed a regulatory dam which caused massive flooding and then drying of the shore, causing the lake and river to get unstable. This caused quite the uproar amongst locals. Two additional dams were constructed later to draw water from the lake. Although these dams generate 70% of the electricity used by the people of Mindanao, the Save Lake Lanao Movement was initiated in 1990 to raise awareness on the extensive downfall of the lake’s ecology because of these plants and pollution.