This research was designed to obtain information on long term changes in water quality of Lake Khurpatal, (Kumaun Himalaya, India). The study was conducted during 2016-17 and 2017-18. The results of the study were compared with the studies carried out about 35 years back. It was noticed that water transparency and concentration of dissolved oxygen in the lake were lowered by 37.5% and 32.2%, respectively in the last 35 years. The water pH was reduced from 8 to 6.7 in the same period of time. The concentration of silica was increased by 26%, however, the lake water was within the set limit of freshwater with regards to salinity. The concentration of PO 4 -P was increased by 26 times while the ammonium -nitrogen and nitratenitrogen increased by 23% and 33%, respectively in last 35 years. The studied parameters of water quality suggested that lake has turned to eutrophic state in this duration.