Assessing the Dynamics of Water Quality and Their Implications on Bio-Chemical Health of River Ecosystem: A RS-Based Study of the Shitalakshya River, Dhaka

Author: Md. Amit Hasan, FarjanaAkther Koly, Sheikh Fahim Faysal Sowrav, S.M. Mustafizur Rahman, Nawshin Alam, Md. Masud-Ul-Alam, Md. Zuhaib Kabir, Shamin Rownok Sarder, Kushik Ahmed
DOI: doi.org/10.70279/bmj-v2-1124

Urban rivers in quickly expanding megacities are frequently severely contaminated, but regular field-based monitoring is difficult because of financial and practical limitations. Using Landsat-8 OLI Level-2 surface reflectance data (2025) and a multi-criteria decision framework, this study assesses the spatial water quality conditions and related biochemical health of the Shitalakshya River in Dhaka. Chlorophyll-a, DO, pH, BOD, COD, TDS, TSS, TP, SPM, salinity, and NDWI were obtained from satellite imagery and incorporated into a River Ecosystem Health Index (REHI) using the Analytical Hierarchy Process (AHP). While the upstream (Purbachal–Demra) and downstream (Bondor–Mondogonj) segments exhibit Good–Excellent conditions over 30–40% of the river, the mid-reach section (Demra–Bondor) forms a continuous Poor–Very Poor REHI hotspot, covering roughly 45–55% of the river length. With COD up to 350 mg L⁻¹, BOD up to 13 mg L⁻¹, TSS up to 1000 mg L⁻¹, and DO continuously below 5 mg L⁻¹ in degraded zones, water quality indicators demonstrate severe organic and particulate stress. The predominance of untreated effluent inputs is confirmed by strong correlations between COD and BOD (R² = 0.958) and suspended loads (R² > 0.91). The satellite data indicators-turned-integrated tool for REHI seems to be an effective approach towards the monitoring of pollution hotspot areas through enaction of rules as well as the restoration of river ecosystems in the more data-poor urban river basins in Bangladesh