Dynamics of pollution and trophic status in selected sub-tropical surface water bodies in Haridwar district, India.

This study provides a detailed approach to evaluating water quality in the Haridwar district, Uttarakhand, India, by integrating physicochemical and microbiological investigations. It employs multivariate analysis and applies water quality and trophic state indices to evaluate the current state of the water and identify potential sources of contamination. The results from the correlation matrix highlight the dynamic interactions between different water quality parameters. Dissolved oxygen, total alkalinity, total suspended solids, biochemical oxygen demand, ammonium nitrogen, fecal coliform, pH, nitrate, and temperature exhibited varying temporal associations. Furthermore, principal component analysis (PCA) identified pH, temperature, and total alkalinity as key influencers across all seasons, while sewage pollution and agricultural runoff were recurring concerns. The enumeration of NSF WQI (National Sanitation Foundation Water Quality Index) (observed from 33.0 to 41.7) further affirmed consistently poor water quality and provided a quantitative metric for a comprehensive assessment. Trophic state index (ranged from 58.6 to 94.2) analysis indicated hyper-eutrophic conditions driven by nutrient concentrations in specific sites, which was further validated by phytoplankton analysis, which revealed the widespread occurrence of cyanobacteria in nearly all water bodies, signaling severe nutrient enrichment and the risk of potential eutrophication. Despite high nutrient levels causing pollution, the water in these water bodies consistently fell within the safe category for irrigation based on estimated sodium percentage, sodium adsorption ratio, and Wilcox diagram. However, it is not recommended to use these surface water bodies for irrigation due to the presence of high levels of organic pollution and a significant load of pathogenic bacteria.