In order to provide the continuity of ecological balance, the presence of water as well as its quality is of capital importance. In this study; a research was carried out about the water pollution in Melendiz stream which feeds the Mamasun dam and meets the drinking and usage water need of Aksaray Plain and its environment. The samples were taken from totally 14 stations between 2006 and 2009 (February, June, September, December) throughout the whole study. These samples were analyzed in terms of 22 parameters, its water quality was determined by evaluating according to "Continental Water Sources Quality Classification Criterions" (Republic of Turkey Ministry of Environment and Forest / Regulation for Water Pollution Control) and thus the factors that cause pollution in Melendiz stream were determined. Moreover, the seasonal variations in quality criterions of Melendiz stream were determined and the precautions necessary to minimize the pollution were discussed. As a result of the research; the effects of domestic wastewater, thermal spring wastewater and wastewater of touristic plants as point pollution sources and agricultural drainage water as a common source were determined. In point sources, organic substances and nitrite were determined whereas, nitrate pollution related with excess fertilizer usage was determined in common sources. The concentrations of these parameters increased especially in dry spells and caused a certain decrease in water quality. According to continental water quality classification criterions, the surface water had IIIrd and IVth class water property in terms of especially nitrate, nitrite and total nitrogen and IInd class water property in terms of other parameters. When the analysis results of samples taken between 2006 and 2009 were compared, it was determined that the amount of pollution increased in time. It was also observed that the surface water of Melendiz stream was exposed to pollution by point and common sources and the quality of water decreased gradually.