Spatial and temporal changes in surface area of Atikhisar Reservoir were monitored by using remote sensing and geographic information system techniques from 1975 to 2017. Satellite images were processed, analysed and manually digitized to reveal the changes in surface area of the reservoir. The results showed that total surface area of the reservoir was ranged between 1.72km(2) and 3.84km(2) during the monitoring period. Maximum increase in the surface area has been observed with 74.6% while maximum decrease has been observed with 31.8%. These fluctuations could be related with the climatic changes, natural and man-made processes such as sediment transportation, water leakages, excessive water exploitation for drinking, domestic or agricultural purposes, and human interventions along the reservoir. Therefore, surface area should be monitored continuously and all factors influencing the variation in surface area should be considered in decision making processes to support water sharing policy toward the management of water resources.