Spatial Prediction of Groundwater Potential of Upper Tigris Basin Mapping in Türkiye with GIS-Based Multicriteria Decision Making (MCDM) Method

Abstract

The Upper Tigris region in the Middle East is in Turkey and this study shows it to be an area with significant water resources that enable agricultural activities in the region. Since the GAP irrigation project, yet to be completed, there is an extensive use of groundwater for irrigation. This situation threatens the groundwater potential of the basin. Therefore, determination of groundwater potential should be evaluated properly instead of relying assessment of the groundwater potential of the region with observation wells, which is a more costly method. In this study, the groundwater potential of the basin was determined by the GIS-based Multi-Criteria Decision Making (MCDM) method; the GIS-based-AHP method is used for identifying the groundwater potential zones of the Upper Tigris Basin as an alternative to expensive and time-consuming method of well drilling. There are 8 key criteria considered; Geomorphology (GM), Geology(G), Line Density (LD), Slope (SL), Drainage Density (DD), Land Use (LU), Rainfall (R), and Soil Type (ST) and the individual weight of each criterion was evaluated by the AHP technique and utilized by the “Spatial Analysis Overlay Weighted Method” obtaining the “Groundwater Potential Index (GWPI)”. The GWPI values obtained is used to classify the Upper Tigris Basin into five categories as follows: 319 km2 of the basin has very poor potential (3.8%); 2217 km2 has poor potential (26.7%); 2800 km2 has moderate potential (33.7%); 2200 km2 has good potential (26.5%); and finally, 763 km2 has very good potential (9.2%).