From Highlands to Wetlands: A Longitudinal Transformation of Water Quality in the Pamba River, Southwest India

The Pamba River is a major west-flowing river of Kerala that supports domestic water supply, agriculture, fisheries, pilgrimage activities, and wetland ecosystems. The present study assesses the spatial variation in physicochemical water quality along two hydrologically contrasting stretches of the river: the highland region of Seethathodu Panchayat and the terminal lowland region of Kainakari Panchayat, during the post-monsoon season of 2023. Surface water samples were collected from six sites in each stretch and analysed for key physicochemical parameters, including temperature, turbidity, pH, dissolved oxygen, nutrients, alkalinity, hardness, calcium, and magnesium, following standard methods. To interpret spatial variability and controlling factors, an integrated analytical framework comprising descriptive statistics, independent sample t-tests, Pearson correlation analysis, principal component analysis (PCA), hierarchical cluster analysis (CA), and Water Quality Index (WQI) was employed. The results revealed significant spatial differences in temperature, turbidity, and dissolved oxygen between the highland and lowland stretches, while nutrient concentrations showed relatively uniform distribution during the post-monsoon period. Multivariate analyses clearly distinguished the two river stretches, highlighting the influence of geomorphology, wetland interaction, and anthropogenic pressure on downstream water quality. Although both stretches fell under the “good” water quality category based on WQI, moderate downstream deterioration was evident. The study provides a robust baseline for future seasonal monitoring and supports integrated river management strategies for the Pamba River basin.