Monsoon-Driven Variability and Long-Term Monitoring of Estuarine Water Quality in the Meghna Estuary, Coastal Bangladesh, Using Geospatial Techniques

Author: Khan Mohammad Ibtehal, Md Ashikur Rahman, Sheikh Fahim Faysal Sowrav, Mohammad Azharul Islam, Rabina Poudyal
DOI: doi.org/10.70279/bmj-v1-1099

Coastal and estuarine ecosystems are vital yet highly vulnerable to climatic variability and anthropogenic pressures that disrupt water quality dynamics. Understanding these varia tions in the Meghna Estuary is essential due to its ecological and socio-economic impor tance to Bangladesh’s coastal communities. The research study aims to examine long-term and seasonal variations in Surface Water Quality Parameters (SWQP) across 33 years (1990–2023) with a six-year interval, focusing on pre-monsoon and post-monsoon condi tions. Multi-temporal Landsat satellite images downloaded from USGS Earth Explorer, were analyzed with the help of ArcGIS 10.7 software deriving ten parameters, including BOD, COD, DO, pH, SST, SSS, SChl, TDS, TSS and Turbidity. Analytical techniques such as the Canadian Council of Ministers of the Environment Water Quality Index (CCME-WQI), Iso Cluster Unsupervised Classification (ICUC), Principal Component Analysis (PCA) and Mann–Kendall (MK) trend tests were employed to evaluate spatial and temporal patterns. The result of the study reveals distinct seasonal contrasts as pre-monsoon waters exhibited higher salinity, TDS, and organic loads, whereas post-monsoon conditions showed elevated turbidity, suspended solids, and chlorophyll-a due to monsoon-induced runoff and sediment transport. The MK trend test and PCA indicated a long-term decline in salinity and dissolved solids, alongside increasing eutrophic tendencies and organic pollution. The CCME-WQI values demonstrated gradual improvement during pre-monsoon but deterioration in post-monsoon periods, reflecting the shifting of hydrological and anthropogenic influences. The study emphasizes the importance of enhancing pollution control policies at the water shed level, rigorously enforcing effluent discharge regulations, and incorporating remote sensing-based monitoring frameworks into national coastal management to ensure sustain able estuarine resource governance in Bangladesh.