Modeling of Harran Plain groundwater potential and quality with geographic information system supported multiple criteria decision making method

There are two important variables in of Harran Plain Groundwater Potential and Quality. These variables are groundwater potential modeling and water quality (pollution). These studies were investigated with Multi-Criteria Decision System (GIS). In this study, the well data about the groundwater potential of Şanlıurfa State Water Works, showing the groundwater level variations which land structure, geology, geomorphology, slope, land use, soil, precipitation, fault intensity and drainage density parameters Groundwater Potential Index (YPSI) of Harran Plain was obtained by using Multiple Assessment Method. According to the ground water potential index, 38% of the basin; medium level, 31%; good level, 29%; bad level, 1.6% of the portion; very good level, very few of them had been found to have very poor groundwater potential. Also by comparing the drilling well data with index water potential index values were overlap with each other. The data related to Harran Plain groundwater quality second part of our study were taken from the water quality study of Yesilnacar (2006) from Harran University Environmental Engineering Department and the opportunities created by GIS program were utilized. Evaluations in 24 wells on the Harran Plain, water quality (pollution) values were transferred to GIS environment by using sodium, pH, EC, nitrate, hardness and irrigation water classification parameters and data related to groundwater quality were obtained. Accordingly, it is concluded that the Harran Plain has high quality waters. One of the reasons Turkey's groundwater contamination, municipal waste and solid and liquid is introduced directly into the soil not subjected to any treatment. Compounds that take longer to break down, such as detergents, can cause serious problems in drinking water by mixing with groundwater. Agricultural activities causing the deterioration of groundwater quality are; pesticide, which is a drug waste, as well as chemical fertilizer and animal wastes. Harran Plain meets most of the need for drinking and irrigation water from groundwater sources. The use of groundwater unplaned and unscheduled can create very important ecological and economic problems. In order to take measures against pollution problems and to establish new policies, it is necessary to record the water usage as a priority and to renew the plans of the subject and, most importantly, to show continuity. Accordingly, GIS (Geographic Information System), ground water and surface water resources, vast land cover of the globe, provides greater benefits and benefits in tracking and recording changes in agricultural activities. Since the Harran Plain is a region where agricultural activities are predominant, nitrate pollution can easily be seen from the maps which have been made more than the desired in these regions. According to the results, it can be said that the criteria that cause nitrate values above the desired limit values in the plain are fertilizers used for agriculture.