Seasonal assessment of physico-chemical parameters and water quality index of Waithou Lake, Manipur, using multivariate statistical techniques

Waithou Lake, a perennial freshwater body in Manipur, has long supported biodiversity, aquaculture, and local livelihoods. However, human activities, intensive aquaculture, and hydrological changes have altered its ecological balance. The present study assessed seasonal variation in water quality at four sites in the lake during the pre-monsoon (PM), monsoon (M), and post-monsoon (PoM) seasons of 2024. A total of 18 physico-chemical parameters were analyzed according to APHA (2017) protocols, and the Water Quality Index (WQI) was computed using WHO standards. Multivariate statistical approaches, including Pearson's correlation, Principal Component Analysis (PCA), and Hierarchical Cluster Analysis (HCA), were applied to assess parameter interrelationships and identify key factors influencing water quality. Results revealed that most parameters were within permissible limits, except for dissolved oxygen, turbidity, and alkalinity, which exceeded the recommended values. WQI values categorized lake water as good to unsuitable across seasons, with only 10% of samples falling into the good category, while 90% were deemed unsuitable. Correlation and PCA indicated strong linkages between EC, TDS, alkalinity, bicarbonates, and nutrient load, while HCA grouped the parameters into three clusters, highlighting their combined influence on WQI. The study concludes that Waithou Lake is experiencing significant ecological stress, with its water quality unsuitable for direct human consumption. The findings provide essential baseline information for sustainable management and conservation of the lake ecosystem. Appropriate measures, such as controlling organic pollution, managing macrophytes and sediments, and implementing community-based monitoring, should be implemented to conserve the lake for the future.