A reflectance-based water quality index and its application to examine degradation of river water quality in a rapidly urbanising megacity

• A reflectance-based water quality index is developed to map river in Dhaka megacity. River pollution and change highly conspicuous since 2010. Surface used reduce background level each rainy season until Excessive load destruction of wetlands possibly accountable for deterioration. The rivers around deteriorating very fast given extensive sources pollutants associated with rapid urbanisation industrialisation. This paper introduced a (WQI) utilising Landsat bands 1 3 (0.45 0.67 µm) against band 5 (1.55 1.75 µm). value the proposed varies from – + 1, whereby 0 (small positive negative) indicated probable contamination, if depth 2 m or above. approach was using data study long-term surrounding megacity, Bangladesh. values were converted total suspended solids (TSS) by observed in-situ data, which showed clear seasonal influence pollution, suggesting it reduces onset high monsoonal flows. However, analysis that remain polluted throughout year, particularly 2011. main reason increasing may be linked contaminant has increased extensively recent years. this other urban rivers, Asia.