Integrated Water Quality Assessment and Ecological Risk Evaluation of Freshwater Ecosystems Under Multiple Anthropogenic Stressors

The threats to the condition of freshwater systems from the impacts of agriculture, sewage, and industry have been increasing, but water quality and ecological risk have usually been evaluated independently of each other. In this study, an assessment was conducted for both water quality and ecological risk at 24 sites, which were reference sites, agricultural sites, and urban and industrial sites in a freshwater system where multiple land uses are observed. The samples were taken in three seasons and were assessed using physical, chemical, nutrient, metal, and biological parameters. Water quality score and four-tiered ecological risk categorization were combined, and the data were analyzed to find their correlations with pollution sources. Reference sites were still healthy, while industrial and urban sites had poor and very poor water quality conditions with the highest levels of ecological risk. Agricultural sites had the highest level of nutrient enrichment, and runoff in the wet season caused poor water quality at all human-impacted sites. Only 5 out of 24 sites were in the good category, and 11 sites were at considerable or high ecological risk levels. There was an extremely high correlation (correlation coefficient = 0.94) between stressor intensity and ecological risk. It is evident from the findings that using both the status of water quality and ecological risk will create a better platform to prioritize pollution abatement and restoration efforts.