Spatiotemporal Dynamics of BOD and COD as Organic Pollution Indicators in Porsuk Dam Lake, Türkiye

Abstract

This study evaluates the spatiotemporal distribution of Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) as primary indicators of organic pollution in Porsuk Dam Lake, Türkiye. Monitoring was conducted during the winter and spring seasons of 2025 across multiple stations. Pearson Correlation Index (PCI) was applied to the dataset to identify the relationship between BOD and COD. Results revealed a significant increase in both parameters during the spring, with the highest levels recorded at station P1. This station, located at the inflow of the Porsuk Stream, is subject to intensive domestic and industrial discharges from Kütahya Province. The near-perfect correlation between BOD and COD confirms a shared origin, primarily linked to municipal and agricultural wastewaters. Conversely, a gradual improvement in water quality was observed toward the dam outlet; stations P4 and P5, located near the dam gates, exhibited significantly lower organic loads, consistent with the natural self-purification processes of the reservoir. Ultimately, these findings underscore that organic pollution is driven by anthropogenic activities, particularly concentrated at the river-lake interface.