Across Southeast Asia, lakes carry everyday life on their waters. Boats connect settlements, fishing grounds feed families, and shorelines preserve stories passed between generations. From Cambodia’s expanding Tonle Sap to Indonesia’s volcanic Lake Toba, their future connects food security, cultural heritage and the health of entire landscapes.
Extraordinary Waters, Different Stories
Southeast Asia’s lakes reveal remarkably different geological histories. In North Sumatra, Toba’s vast basin was shaped by a supervolcanic eruption approximately 74,000 years ago. UNESCO recognised Toba Caldera as a Global Geopark in 2020, highlighting both its geological significance and the cultural heritage of surrounding communities.
The region’s deepest lake, however, is Matano in South Sulawesi. Indonesia’s conservation authority records its maximum depth at approximately 590 metres. Formed through tectonic processes, Matano connects through an outlet to Mahalona and Towuti, forming part of the Malili lake system. Its story demonstrates why Southeast Asia’s inland waters cannot be understood through volcanic landscapes alone.
Cambodia’s Tonle Sap offers another distinction: Southeast Asia’s largest freshwater lake changes dramatically with the seasons. The Mekong River Commission describes its surface expanding from approximately 2,500 square kilometres to around 15,000 square kilometres during peak flooding. These figures describe a seasonal range, rather than a fixed size reached every year.
A Seasonal Pulse That Feeds Communities
Tonle Sap’s productivity depends on its connection to the Mekong. During the wet season, rising Mekong waters reverse the flow of the Tonle Sap River, pushing water into the lake. Flooded forests and surrounding wetlands become feeding and nursery grounds for fish.
As waters recede, fish move through the connected river system. The Mekong River Commission and Cambodia’s Fisheries Administration have monitored the Tonle Sap River’s stationary-net fishery since 1995, tracking migrations that link seasonal flooding with livelihoods.
For fishing households, the timing and duration of flooding can be as consequential as the amount of water. Changes to river flows, habitat loss and fishing pressure affect what families can catch, eat and sell. Protecting the lake therefore requires attention to the wider basin, including decisions made far upstream.
Indonesian limnologist Arianto Budi Santoso expressed the broader management challenge in a BRIN discussion reported in May 2024.
“Lake problems are not only technical but also socioeconomic,” he explained, translated from Indonesian, calling for collaboration across disciplines and institutions.
Keeping Fish Farming Within Nature’s Limits
Aquaculture provides income and food, but productive lakes also have ecological limits. Fish cages concentrate animals, feed and waste in particular areas, making stocking levels and water quality central to responsible management.
Taal Lake in the Philippines illustrates the financial consequences when that balance breaks down. In June 2019, the Bureau of Fisheries and Aquatic Resources reported that depleted dissolved oxygen had caused losses exceeding 600 metric tonnes of tilapia, valued at approximately ₱43.13 million.
The agency identified weather conditions and overstocking among the contributing factors. Its response included water monitoring, emergency harvesting advice and guidance on appropriate feeding and stocking density.
The lesson extends beyond a single incident. A lake’s contribution to food security depends on maintaining conditions that allow fish to survive. Monitoring and timely advice protect both ecosystems and the investments of producers.
Waterways That Carry Culture
At Myanmar’s Inle Lake, navigation, fishing, commerce and floating vegetable gardens form an interconnected way of life. Gardens established on floating rafts and distinctive waterside homes demonstrate how communities have adapted their livelihoods to the lake.
These landscapes also show how environmental pressures overlap. UNDP has documented the effects of unsustainable resource use, invasive species, deteriorating water quality and tourism development around Inle. Conservation involves the surrounding watershed as well as the water itself.
Speaking at an Inle conservation workshop in 2018, Biplove Choudhary, then chief of UNDP Myanmar’s Sustainable Inclusive Growth unit, stressed the importance of coordinated management.
“A strengthened Inle Lake Management Authority will play a key role in ensuring the sustainability of current and planned conservation efforts,” he said.
At Toba, the relationship between landscape and culture offers another approach to understanding a lake. Traditional houses and museums introduce visitors to the heritage of Batak Toba, Simalungun, Karo and Pakpak communities. Geology provides the setting; local knowledge gives the landscape its human depth.
Sharing Solutions Across the Shoreline
Regional cooperation can begin with practical exchanges between communities. An initiative launched in 2016 connected residents of Cambodia’s Tonle Sap and Thailand’s Songkhla lake basin through participatory video production.
Supported by the Mekong River Commission, participants documented fish conservation, women’s roles in disaster preparedness and youth climate action. Community screenings helped residents compare experiences and discuss possible solutions. This was cooperation through shared knowledge, grounded in the daily concerns of people living beside water.
Southeast Asia’s lakes deserve attention beyond their scenic appeal. Their lasting value lies in healthy fisheries, dependable connections and living cultures. Protecting those benefits means giving lakeside communities a meaningful role in decisions about the waters that sustain them.
