Ecological and conservation status of the wetlands of Dhaka city

Abstract

The rapid urbanization and population growth in Dhaka, the capital city of Bangladesh, have dramatically altered its landscape, placing wetlands under unprecedented threat. This study aims to evaluate the current state of wetlands in Dhaka City, identify factors contributing to their depletion, explore the diversity of aquatic flora and fauna, and develop a conservation strategy to restore degraded wetlands for a healthier environment. For this investigation, twelve sampling locations were selected across different regions of Dhaka, including the Buriganga River, Turag River, Balu River, Ramna Lake, Dhanmondi Lake, and Gulshan Lake. Data were collected through field observations over two years, from June 2019 to June 2021, involving the collection of water and plankton samples every three months at selected sites around Dhaka City. Laboratory analyses were conducted to assess zooplankton status and water quality parameters. Secondary data were sourced from the internet, journal articles, books, and various departments and institutes within the University of Dhaka. The study reveals significant relationships between physico-chemical parameters and zooplankton abundance, showing seasonal and spatial variations in Dhaka City's water bodies. It identified 22 genera from 5 zooplankton groups at the study sites, with Rotifera (40.9%), Cladocera (31.81%), and Copepoda (13.63%) being the most dominant. Zooplankton abundance peaked in the winter and rainy seasons and was lowest in the summer, providing insights into their periodicity in Dhaka City water bodies. Physico-chemical parameters varied seasonally across sampling stations, with the highest temperatures recorded in the Buriganga River and the lowest in Ramna Lake. Dhanmondi Lake had the highest pH, while Ramna Lake had the highest dissolved oxygen (DO), and Turag River had the lowest pH and DO. Total Dissolved Solids (TDS) were highest in the Turag River and lowest in Dhanmondi Lake, while other parameters like EC, NO2-N, NO3-N, and NH3-N showed the highest levels in the Balu River and the lowest in Ramna and Dhanmondi Lakes. The study highlights a significant reduction in the total area of water bodies, indicating a sharp transformation in Dhaka City's wetland landscape. It underscores the imminent threat of depletion due to urbanization, resource overuse, and pollution, recommending urgent measures such as restoration, sustainable management, and community involvement to protect Dhaka's wetlands.