Impact of landscape patterns on spatial and seasonal water quality: an insight from the Sub-Himalayan rivers in Siliguri Planning Area, India

Rapid urbanization significantly influences the quantity and quality of natural water resources. This study investigates the impact of urban growth on the water quality of the Balason and Mahananda rivers in Siliguri. To evaluate the Water Quality Index (WQI), water samples for eleven physicochemical parameters were collected from seventeen selected sites. An upper – urban – downstream gradient approach was adopted, integrating statistical and GIS-based techniques for comprehensive analysis. WQI results indicated a marked decline in water quality during the lean season, particularly in densely populated urban stretches. Average WQI scores ranged from good to poor, with the most degraded sites located within the central urban zone. Statistical assessments revealed significant spatial variation in water quality across upstream, urban, and downstream segments. This research highlights that improving urban water quality aligns directly with SDG 6 (clean water and sanitation), suggesting the urgent need for integrated water resource management and sustainable urban planning.