Evaluation of groundwater quality using a GIS-MCDA-based model: a case study in Aksaray, Turkey

Evaluation of water resources and the protection of these resources from environmental pollutants is a difficult and complex process. In this study, a development of model to estimate the water quality and identify the most suitable regions based on good water quality was aimed. For this purpose, 40 water samples were taken through water wells in Aksaray region of Turkey. A groundwater quality index (AWQI) based on water chemistry data has been developed to assessment the groundwater quality using the techniques of the multi-criteria decision analysis. Based on this index, four suitability classes were defined as excellent, good, permissible and unsuitable. Kriging method was used to determine the spatial distribution of groundwater quality parameters in the study area. For each map, different semivariogram models were tested by cross-validation and the best model was selected. The exponential model having a minimum standard error was selected the most suitable model for deriving water quality maps. The areas that are excellent for groundwater quality are concentrated in the northeastern and southeastern parts of the region where the AWQI-II scores were greater than 0.9. This study provides general information on how to determine the spatial distribution of the groundwater quality and identify the performance scores of criteria affecting water quality in inland aquifers.