Appraisal of water quality in the Lakes of Nainital District through numerical indices and multivariate statistics, India

Nainital district is naturally gifted with numbers of natural water bodies. Among these water bodies, the four lakes (Nainital, Bhimtal, Naukuchiatal and Sattal) are the major source of freshwater for the local inhabitants and industries situated in surrounding area. However, the lakes receive an enormous amount of untreated wastewater which imbalances the nutrients concentration in lake water. Therefore, the present study is focused to assess the water quality using water quality indices (NSFWQI, CPI and HPI) based on the concentration of parameters (like DO, BOD, heavy metals, etc.) in the lakes. The envirometric applications (HCA and PCA) were also used to identify the similarity in pollution load at sampling locations and the source of factor responsible for pollution in the lakes. The water samples were collected in pre- and post-monsoon months in the year 2014–2015, from 12 sampling locations. The results indicate that the water quality of lakes is unsuitable for drinking, as the average CPI was 0.90 and 0.88 in Bhimtal Lake, 1.42 and 1.43 in Nainital Lake, 1.19 and 1.27 in Naukuchiatal Lake, 1.46 and 1.42 in Sattal Lake in pre- and post-monsoon months, respectively. The HPI was found more in Nainital Lake than in rest other three lakes, while risk assessment index (RAI) was found in range RAI > 1 in the four lakes. HCA gained two clusters and PCA gained two PCs, which indicate the impact of both anthropogenic and natural sources for deterioration of water quality. Therefore, it has been suggested that the lake water must be treated before used for drinking.