Seasonal fluctuations in water temperature and dissolved oxygen: A comparative study of oxbow lakes along the Kapuas Riverine System

Lake Keliling and Lake Baru are oxbow lakes located along the Kapuas River, the largest river in West Kalimantan. This study aimed to analyze the variations in water temperature and dissolved oxygen (DO), and their relationship with fluctuations in the main river during the dry and wet seasons. We measured water temperature and DO parameters at Lake Keliling and Lake Baru in February and September 2023 for wet and dry seasons, respectively. Moreover, we installed a camera for monitoring the river water level fluctuations at both locations. In addition, we obtained the secondary data for water level and water quality data (2021 – 2022 and 2018 – 2022, respectively) close to both sites. The result showed during the wet season, the vertical distribution pattern of DO in Lake Keliling and Lake Baru showed a similar pattern to temperature. Anoxic conditions in Lake Keliling during the rainy season were observed at a depth of 2 meters, whereas in Lake Baru, these conditions were found at depths of 6 to 8 meters. During the dry season, the depth of the anoxic water column in Lake Keliling remained at 2 meters, while in Lake Baru, the anoxic layer shifted to a shallower depth of approximately 1.8 meters, except at Station Baru 3. This indicates the potential for sediments to store heat at shallow depths. It could be explained that the variability of water temperature and DO parameters, was likely various changes related to the water level conditions (dry and wet seasons).