Assessment of irrigation water quality by a Geographic Information System-Multicriteria Decision Analysis-based model: A case study from Ankara, Turkey.

In this study, the irrigation water quality of Eryaman region in Ankara (Turkey) has been investigated using a Geographic Information System-Multicriteria Decision Analysis (GIS-MCDA)-based model. Two different irrigation water quality indices (IWQI-A and IWQI-B) based on Analytic Hierarchy Process (AHP) and Data Envelopment Analysis (DEA) have been developed to provide a single suitability score for all criteria of irrigation water quality. The irrigation water quality indices were composed of 3 main criteria and 11 sub-criteria. Based on irrigation water quality indices, four suitability classes have been identified as (a) excellent, (b) good, (c) permissible, and (d) unsuitable. Irrigation water quality maps were created by using kriging method and the water quality index scores. The temporal variation of irrigation water quality was evaluated using the models created for July 2007, 2010, and 2015 years. The most suitable areas for irrigation water are concentrated in the eastern and western parts of the region where the IWQI-B scores were >0.85. In recent years, the deterioration in irrigation water quality has increased in the southern parts of the basin. This research has demonstrated that the indices created by using DEA and AHP methods are reliable indicators to assess irrigation water quality. PRACTITIONER POINTS: Water quality indices can be used to depict the overall water quality status in water management planning. To avoid problems when modeling groundwater quality, the factors that have the most effect on water quality should be selected. Analytic Hierarchy Process and Data Envelopment Analysis techniques are efficient and reliable methods to determine water quality.