The present study has been carried out to study the status of primary productivity in relation to physiochemical parameters of the Kadwai reservoir of Ratnagiri district, Maharashtra. The primary productivity was determined by estimating gross and net primary productivity. The experiment was conducted during the monsoon and post monsoon seasons from 1^st June to 30^th Nov 2015 to know the effect of organic run off on primary production of Kadwai reservoir. The physiochemical parameters such as temperature, pH, dissolved oxygen, total hardness, total alkalinity and transparency ranged from 27^oC-30.5^oC, 7.5-8.6, 3.2-7.0 mg/l, 46-75 mg/l, 56-95 mg/l, and 118-130 cm, respectively. The gross primary productivity (GPP) during monsoon was 0.07-0.11 gC/m³/hr in June, July and August 2015, respectively, which was very low, whereas GPP were increased during post monsoon season. The values were recorded as 0.12-0.48 gC/m³/hr in the months of September, October, and November 2015, respectively. The results indicated that during monsoon season, organic load is coming along with water in to the reservoir, but phytoplankton growth is minimum due to the heavy rain and flushing rate were high from the downstream of the reservoir. During post monsoon, primary productivity was increased. The results indicate that Kadwai reservoir is more productive during post monsoon season suitable for stocking fish seed.