Assessment of the Seasonal Variations of Lakes Water Quality in Bangladesh

The study was conducted to assess the seasonal variations of water quality in Hatirjheel Lake and Dhanmondi Lake during the period from August, 2019 to January, 2020. The water samples were collected monthly during the monsoon and postmonsoon seasons from five sampling stations of both lakes. Comparative analysis revealed that mean pH was near the standard level in both lakes where DO concentration was much lower in Hatirjheel Lake than Dhanmondi Lake which could be due to the direct dumping of nearby residential and commercial waste, and domestic sewages from the city drainage system as well. The BOD concentration in Hairjheel Lake water exceeded the standard in both seasons and there was no significant change over seasons. In contrast, the Dhanmondi Lake water showed relatively lower BOD concentrations in both seasons where mean concentration slightly exceeded the standard in some stations. The EC and TDS contents showed positive relations but exceeded the standard limit throughout seasons in both lakes. The nutrient contents (NO3 -, NO2 - and NH4 +) of Hatirjheel Lake water highly exceeded the standard during the study that tends the lake water prone to eutrophication. The study revealed that the physicochemical parameters and nutrient status of Dhanmondi Lake water were within the standard limit except EC indicating a rich habitat for aquatic organisms and sounds for recreational activities than Hatirjheel Lake which should be monitored throughout the year to maintain the productivity of lake water systems.