Water pollution and quality assessment of Meda Ela (Mid Canal), Kandy, Sri Lanka: Impact of urbanization – A preliminary study

Meda Ela (Mid Canal), a small but ecologically significant tributary of the Mahaweli River in Kandy, Sri Lanka, is under increasing pressure from urbanization and high population density. This study examines the impacts of unplanned urban development on water quality in this tropical, mountainous urban area. Temporal and spatial water samples were collected along the tributary and analyzed for key chemical parameters, including dissolved oxygen (DO), biological oxygen demand (BOD), nitrite (NO₂⁻), nitrate (NO₃⁻), and phosphate (PO₄³⁻). Results indicate critically low DO levels (<2.0 mg L⁻¹) in densely urbanized sections. Nitrite concentrations exhibit a strong negative correlation with DO, while nitrate shows a strong positive correlation, likely reflecting denitrification by facultative bacteria under anoxic conditions. Principal component analysis identifies the fourth sampling location (the first underground section) as the most polluted site. Downstream trends reveal increasing concentrations of most pollution indicators, except nitrate, accompanied by decreasing DO. Additionally, the stream suffers from high levels of solid waste and aesthetic degradation. These findings highlight the urgent need for sustainable urban planning and effective wastewater management to preserve this tributary’s ecological integrity.