29. Remote Sensing of Water Quality Parameters Along the West Bengal Coast of India

Satellite remote sensing of coastal water quality using the sensors that operate in the visible and near-infrared (NIR) bands for measuring ocean colour and estimation of Sea Surface Temperature (SST), is extensively carried out across various regions. The present study focuses on the analysis of water quality on the east coast of India using Landsat 8 OLI/TIRS (Level-1C), 30 m resolution data for the period 2016–2019. The parameters that could be measured using remote sensing through various band combinations are Chlorophyll-a, Coloured Dissolved Organic Matter (CDOM), Total Suspended Matter (TSM), Turbidity. Reflectance data is converted into radiance, later on land masking and atmospheric corrections were carried out for the cloud free images. Algorithm used for the estimation of chlorophyll-a is OC2, which is a ratio of band 2 (483 nm) and band 3 (561 nm) that varies between 0 and 6 mg/m³. CDOM is derived using ratio of band 3 (561 nm) and band 4 (655 nm), wherein the values range from 0.785 to 8.58 m⁻¹. Turbidity is derived using ratio of band 3 (561 nm) and band 4 (655 nm). Turbidity along the coast is observed to be in the range of 4–21 FTU (Formazin Turbidity Unit). CDOM is predominant near the mouth of River ‘Mahanadi’ inferring that this has originated in the catchment area rather than the one generated in the Bay of Bengal. The impact of rainfall, discharge and cyclones on the water quality variability along the coasts of West Bengal, Odisha and Andhra Pradesh is assessed in the present study. Similarly, the anthropogenic impact on the turbidity, suspended matter and chlorophyll is assessed.