Impacts of rapid urbanization on long-term water quality of the peripheral River of Dhaka, Bangladesh

This study was carried out to determine the current state of the physicochemical water quality parameters and the effects of urbanization over 50 years in the peripheral rivers by using primary and secondary data adjacent to Dhaka city. These rivers and waterways had DO levels much below the recommended standard of Bangladesh, and occasionally, they even approached 0. This suggests that the water in these rivers is highly polluted and unfit for aquatic life. For the most part, high rates of pollution also contribute to high BOD readings. Besides, the weighted arithmetic method discovered that the urban rivers have deficient water quality, which requires immediate attention. Compared to the seasonal variations, the water quality is worse in the dry season compared to the wet season. Among all the rivers, the lowest WQI found was 11.89 in the wet season and 123.65 in the dry season. Moreover, the Heavy Metal Pollution Index (HPI) calculation was done, with data from 1 to 3797 indicating that most heavy metal data sets are unsuitable for drinking and household uses. The current study found that built-up areas have grown 288%, and the water bodies have declined by 60% over the last 30 years. This study shows that the quality of peripheral river water in Dhaka city hinders the objectives of the SDG 6 Goal: Clean Water and Sanitation. Revitalizing the water supply requires the attention of the city authorities.Practitioner Points Rapid urbanization has made Dhaka one of the least habitable cities, with industrial growth contributing significantly to pollution. DO levels are far below than Bangladesh's standards, sometimes approaching zero, making the water unfit for aquatic life. The study reveals a decline in water quality, especially during the dry season, and WQI indicates extremely low standards. Built-up areas have increased by 288%, while water bodies have decreased by 60% over the past 30 years.