Hanjalutung Lake Expedition: Tracing the History of a Peatland Oxbow Lake

Hanjalutung Lake is a peatland oxbow lake, a type of floodplain lake formed when a river meander becomes cut off from the main channel, creating an isolated water body often referred to locally as a kali mati. These lakes represent dynamic freshwater systems that archive environmental change while providing essential ecological functions.

Located in Petuk Katimpun Village, approximately 10 km from Palangka Raya, Hanjalutung Lake covers an area of about 11.7 hectares, with a length of nearly 2 km, a width ranging from 100 to 150 meters, and depths reaching up to 8 meters. Although the lake maintains a hydrological connection with the Rungan River, its water level fluctuates dramatically in response to seasonal flooding, reflecting the natural dynamics of the surrounding floodplain.

Oxbow lakes play a critical role in floodplain ecosystems. They function as freshwater habitats, flood buffers, regulators of biogeochemical cycles, and providers of diverse ecosystem services for both wildlife and surrounding communities. Encircled by peat swamp forest, Hanjalutung Lake exhibits distinctive hydrological, chemical, and biological characteristics shaped by organic-rich sediments and acidic waters typical of tropical peatland environments.

From a global environmental perspective, the lake holds particular significance due to its role in carbon storage. In Central Kalimantan, more than 95% of peat swamp forest carbon reserves are stored within sediments, making peatland lakes like Hanjalutung vital components in carbon sequestration and climate change mitigation. However, these systems are increasingly threatened. Land conversion for agriculture and plantations has intensified erosion and sedimentation processes, pressures that are further amplified by climate change–driven hydrological extremes.

Despite its ecological importance, fundamental questions remain unanswered: When did Lake Hanjalutung form, and when did significant environmental changes begin? These questions can be addressed through paleolimnological approaches, which reconstruct past environmental conditions using sediment records as natural archives.

For this reason, the study was conducted as part of the Oxbow Lakes Expedition: Hanjalutung Lake, aiming to uncover the lake’s formation history, environmental trajectories, and responses to both natural and anthropogenic drivers. The expedition contributes critical baseline knowledge needed to support peatland conservation, sustainable land management, and long-term climate resilience strategies.