SPATIO-TEMPORAL VARIATION OF WATER QUALITY PARAMETERS AND SEDIMENTS ORGANIC MATTER IN RELATION TO DEPTH OF THE KAPTAI LAKE, RANGAMATI

Abstract

The present study was carried out to reveal the physical and chemical status of the Kaptai Lake, Bangladesh. From four sampling points (Jolojan Ghaat, Kandemu, Shubholong Jhorna and Shubholong Bazar), water samples were taken over a period of 6 months from September, 2021 to February, 2022. Temporal variations in physical and chemical parameters were discovered in all cases. Highest air temperature (32.8°C) was recorded in October 2021 and the lowest (24.1°C) in January 2022. On the other hand, the water temperature varied from 21.9°C in January 2022 to 31.6°C in October. The value of dissolved oxygen (DO) was found to fluctuate from the minimum value of 5.5 mg/l in September to the maximum value of 8.30 mg/l in November. The maximum free CO2 value was 6.5 mg/l in February and the minimum value was 2.3 mg/l in November whereas the pH of the water was always found to be alkaline in nature and varied between 7.30 and 9.02. The total alkalinity value fluctuated from 62.8 mg/l in October to 89.10 mg/l in January whereas the hardness of lake water varied from 55.7 mg/l in September to 85.68 mg/l in February. The lowest concentration of NH3-N was found at Shubholong Jhorna (0.018 mg/l) in October and the highest concentration was found at Kandemu (0.49 mg/l) in February. The highest and lowest organic matter was 6.32 % and 4.09 %, with a mean value of 5.50 ± 0.55%. Water temperature and dissolved oxygen concentration were higher in the surface water whereas the TDS was higher in the bottom water. The physical and chemical characteristics of lake water were found to be within the ranges that were suitable for the survival of aquatic life, including the production of fish by supporting a good ecosystem. The current study offers baseline data on Kaptai Lake's physical and chemical parameters' monthly changes, which will be useful for the lake's significant ecosystem's sustainable management and preservation.