Spatial Assessment of Organic Pollution in Three Major Lakes of Türkiye: A Comparative Analysis of BOD and COD Levels in Manyas, Uluabat, and İznik Lakes

Marmara Lakes BOD-COD

Abstract

This study investigates the spatial distribution and comparative water quality status of Manyas, Uluabat, and İznik Lakes using Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) as key indicators of organic pollution. Water samples collected in spring 2025 were analysed, and GIS-based mapping approaches was applied to reveal spatial variability and pollution patterns. Results showed that Uluabat Lake generally exhibited good water quality with low organic load, İznik Lake reflected mostly moderate conditions with localized impacts, while Manyas Lake displayed considerably higher BOD and COD values, indicating stronger organic pollution pressure. According to the Turkish Water Pollution Control Regulation, Manyas Lake was classified at higher pollution classes in several stations, whereas the other two lakes remained largely within lower classes. Overall, the findings highlight clear differences in anthropogenic pressure among the studied lakes and emphasize the importance of continuous monitoring and effective watershed management to protect these ecologically and economically significant freshwater systems.