Develi Closed Basin is located at the south-western side of Erciyes Mountain, in the Central Anatolia. Sultansazligi Wetland is located in Develi Closed Basin, which is one of the seven important wetlands of Turkey and the second important bird habitat of Turkey. Sultansazligi is also known as one of the most important wetlands of the Eastern Europe and the Middle East. In the recent years, this wetland faced with the water shortage and salinity, due to the climatic change and irrigation return flow with the high salt content. There is an intensive irrigation around the marsh with abundant use of water due to the wild flooding. In this study, the water budget of Develi Closed Basin is computed and the uncertainties faced during the water budget computations are introduced. Uncertainties of the Develi Closed Basin water budget computations; can be summarized as the unknown hydrological parameters such as missing flow data, infiltration index of the soil, evapotranspiration from the reedfield, insufficient flow and precipitation data.