The Bhatsa River originates in Igatpuri, Maharashtra, and converges with the Ulhas and Kalu Rivers. This river is a major source of drinking water for the local population and the Mumbai Metropolitan Region (MMR), and supports rich flora and fauna, but also receives pollutants from agriculture, fishing, dredging, and industry. This study examines the seasonal variations in the physicochemical and biological parameters of the Bhatsa River. Significant seasonal fluctuations were observed in turbidity, dissolved oxygen, nutrients and microbial counts. Bhatsa River water quality was evaluated using a multi-parameter Water Quality Index (WQI) at eight stations(S1-S8) from January 2020 to September 2025 across pre-monsoon, monsoon and post-monsoon seasons, measuring monthly pH, dissolved oxygen, biochemical oxygen demand (BOD), chemical oxygen demand (COD), nitrate, fecal coliform(MPN), through Laboratory analysis in accordance with corresponding IS standards and NSFWQI. Mean WQI showed Excellent conditions at upstream S1 (88.43), Good quality at midstream stations S2–S7 (≈78–83), and Poor quality at downstream S8 (56.16), where 69.6% of samples were Very Poor with markedly elevated BOD, COD, and fecal coliform. Kruskal–Wallis tests indicated highly significant spatial differences for all parameters and WQI (p < 0.001), while temporal analyses revealed significant WQI decline at S2 and S3, additional concern at S7, increasing pH and nitrate at all stations and sharply rising fecal coliform at S8. Seasonally, WQI was highest in pre- and post-monsoon and lowest during the monsoon, reflecting runoff, dilution, and pollutant loading dynamics. Strong negative correlations of WQI with BOD, COD, and fecal coliform, and positive correlation with dissolved oxygen, highlighted the dominance of organic and microbial pollution, whereas clustering and a pollution severity index delineated three zones: pristine upstream (S1), moderately impacted midstream (S2–S7), and a critical downstream hotspot (S8). Land cover data were obtained from the Esri Sentinel 2 10 m Land Use/Land Cover Time Series, produced by Impact Observatory, Microsoft, and Esri from ESA Sentinel 2 imagery and accessed via the Esri Land Cover Explorer (ArcGIS Living Atlas of the World). Land-cover analysis reveals rapid peri-urban transformation (2017–2024), with built-up area doubling from 3.4% to 7.4% alongside sharp declines in tree cover (21.7% to 14.0%), signalling urgent needs for sustainable planning. The findings confirm a progressive upstream–downstream deterioration in Bhatsa River water quality, with statistically significant inter-station differences and emerging temporal degradation at key midstream sites. These patterns underscore the need for targeted management, including urgent intervention at station S8 and stricter basin-wide control of organic and microbial pollution sources. Seasonal runoff and anthropogenic inputs are shown to exert a strong influence on water quality dynamics, further complicating the river’s ecological resilience. Importantly, the integration of hydrological modelling with water quality assessment provides a comprehensive framework to disentangle natural variability from human-induced pressures, offering critical insights into the drivers of river health and guiding sustainable management strategies.
AGRE et al. (Thu,) studied this question.