Vol. 9, Special Issue 4, Part G (2025)

Urban water bodies are vital for human settlements and provide various ecosystem services to city dwellers; however, they face significant environmental strain as cities expand. This study compared ten physicochemical parameters, zooplankton diversity, and water quality between a natural oxbow lake (Moti Lake) and a pond (Atal Pond) in a densely populated town (Motihari) of Bihar, India. Water samples were collected and analyzed weekly during the study period from July 2023 to June 2024. Altogether, five samples from Moti Lake and one from Atal Pond were collected every week. Independent t-tests were used to assess the differences in the mean value of physicochemical parameters, while zooplankton diversity was evaluated using Shannon, Simpson, and Pielou indices. The Weighted Arithmetic Water Quality Index (WAWQI) determined overall water quality. Results indicated significantly poorer physicochemical quality in the lake (p < 0.05 for all parameters) except Temperature and Dissolved Oxygen [DO]. The lake exhibited higher zooplankton diversity and species richness but similar evenness to the pond. A preliminary examination of water quality indicated both water bodies were unsuitable for human use, with the lake scoring poorer on WAWQI. These findings underscore the need for targeted action to rejuvenate the Moti Lake.