Lakes are one of the important sources of potential primary production in the world. Primary production is the most important biological phenomenon in nature on which the entire diverse array of life depends, either directly or indirectly. It is concerned with evaluation of the capacity of an ecosystem to build up primary organic compounds, using radiant and chemical energy, for transformation and flow to a higher-level trophic system. Phytoplanktons act as primary producers and their physiological activities are greatly controlled by physico-chemical characters of the water body. During photosynthesis, Primary producers produce a wide range of organic compounds, release oxygen as a byproduct to the surrounding waters. Measurement of primary productivity provides information about the photosynthetic production of organic matter and becomes the basis for the functioning of ecosystem. It is influenced by a combination of physical, biological factors and sunlight provides the energy for photosynthesis. It is adversely affected by anthropogenic activities. In the present study, seasonal variations of primary productivity in terms of NPP, GPP and CR of water was studied using Light and dark bottle method of Gardner and Gran (1927) for a period of one year from February-2014 to January-2015 at two sites of Durgada Halli lake.