Most of the non-irrigated areas in the southeast of the Harran Plain are irrigated by groundwater. The aim of this study is to determine the importance of 13 underground irrigation water sources operating in the agricultural areas of Ohali village in southeast of Harran Plain in Sanliurfa province in terms of some quality characteristics and irrigation. In this context, the waters belonging to 13 underground wells were analysed and examined in terms of irrigation water quality. According to the results of the analysis, the electrical conductivity of water samples was measured between 1127-4090 µS/cm. The SAR value of irrigation water was found to be between 1.05-3.41 and the %Na value was between 16.2% - 31.8%. In the evaluation made according to four different classification systems, in general, waters 6, 7, 8 and 9 were determined as the worst quality in all classification systems. These waters are described “unsuitable” irrigation water. Considering that the plants which have high water consumption such as cotton and corn are cultivated in the region, it is foreseen that if the necessary precautions are not taken, the salinity in the soil will increase and yield losses will be high. It is imperative that these areas, which cannot be irrigated within the scope of GAP irrigation project, be irrigated with clean water as soon as possible. However, an appropriate drainage system must be installed in the area.