The present study aims to assess the water quality of Senchal Lake, the main source of drinking water for Darjeeling Hill town, covering the time period of 2011–2020. A total of 14 water quality parameters were considered to evaluate lake water quality. The annual mean values of measured water parameters were within the desirable limits for drinking water (BIS, in 2012 Indian standard for drinking water specification 2012 second revision. Bureau of Indian Standards, New Delhi, 2012; WHO, in Drinking water guidelines World Health Organization standard 2006. World Health Organization, Geneva, 2006). Water Quality Index (WQI) was employed to assess the lake’s health and to classify the lake water quality. The calculated WQI values ranged between 13.21 and 105.58 during the period of 2011–2020. Year-wise WQI values revealed mostly ‘Excellent to Good’ types of water quality, except in 2013, when water quality was recorded to be ‘very poor’. Various statistical tools such as Pearson’s correlation study, principal component analysis (PCA), and cluster analysis (CA) were employed in order to identify the factors which influence the lake water quality. The results of statistical analyses (PCA and CA) have demonstrated that geogenic sources, catchment features and temporal variations are the major factors which influence the lake water characteristics, with limited contributions from anthropogenic sources. The observation has shown an increasing trend of nutrient enrichment (NO3– 0.27 ± 0.15; PO43– 0.17 ± 0.38) which may lead to the onset of eutrophication in the near future. Therefore, it is important to identify the sources of nutrients in lake water and address this on an urgent basis. Additionally, regular monitoring of the water quality and the proper execution of effective management plans are essential to protect this lake and its water resources.