Combining AHP with GIS for assessment of irrigation water quality in Çumra irrigation district (Konya), Central Anatolia, Turkey

Çumra irrigation district (ÇID) is one of the most important agricultural production regions in Central Anatolia. Surface water in the region is limited and agricultural production substantially relies on groundwater irrigation. In this study, analytic hierarchy process (AHP) is combined with geographical information systems (GIS) to assess the irrigation water quality in the aquifers of ÇID. Nine water quality criteria were classified into four main hazard groups including salinity hazard, infiltration and permeability hazard, specific ion toxicity, and miscellaneous impacts on sensitive crops. A weighting coefficient of each criterion was determined by using GIS-based AHP. Nine thematic maps defining the electrical conductivity (EC), total dissolved solids (TDS), sodium adsorption ratio (SAR), combined EC-SAR, chloride, boron, nitrate–nitrogen (NO₃–N), bicarbonate, and pH were generated to develop the suitability map for irrigation water quality. Based on the results of this application, the final irrigation water quality index model was classified into three groups as high, moderate, and low suitability for irrigation purposes. The derived suitability index map for irrigation water quality indicates that the aquifer water in 61.92 % of the study area has high suitability for irrigation water, moderate suitability in 19.20 %, and low suitability in the remaining 18.87 %. The suitability index map for irrigation water quality explicitly shows that most of aquifer waters in ÇID are highly suitable for irrigation purposes while the groundwater quality deteriorates towards the north–northeastern and the eastern directions.