Trophic State Index (TSI) of Nainital lake has been determined using secchi disk transparency as well as using Landsat 7 ETM bands. The insitu water quality parameters like pH and dissolved oxygen (DO) have been measured using multiparameter water quality instrument TROLL 9500. Various interpolation techniques have been tested and the best one has been applied to prepare the water quality images of Nainital lake. The analysis of Landsat images have shown that the lake water is in eutrophic condition from the year 2000 to 2010. However, the trophic state index values are found to be relatively less during the year 2006 to 2008. This may be due to the lake restoration programmes undertaken by the Lake Development Authorities.