Spatial and temporal mapping of groundwater salinity using ordinary kriging and indicator kriging: The case of Bafra Plain, Turkey

Groundwater salinity contributes significantly to soil salinization in irrigated areas. In this study, spatial and temporal analyses of groundwater salinity were performed based on data from 97 wells monitored over a 7-year period. ArcGIS Geostatistical Analyst was used in exploratory data analysis, semivariogram model selection, cross-validation and development of a groundwater salinity distribution pattern. Groundwater salinity semivariogram models varied by year and included exponential (2004, 2009), spherical (2005), J-Bessel (2006) and rational (2007, 2008, 2010) models. Ordinary Kriging (OK) was used to analyze spatial variability of groundwater salinity, whereas Indicator Kriging (IK) was used to analyze groundwater salinity in relation to pollution threshold values.Spatial variability maps show a decrease in groundwater salinity from 2004 to 2010, with salinity levels in 31% of the study area exceeding 5.0 dS m−1 in 2004, compared to 9% of the study area in 2010. Moreover, probability maps show that 13.60% of the total area had the highest probability (0.8–1.0) of exceeding the threshold in 2004, compared to 0% in 2010.

► Groundwater salinity were measured at 97 wells from 2004 to 2010.
► Groundwater salinity values interpolated using ordinary kriging and indicator kriging.
► The best-fitted theoretical model was selected based on the lowest RMSE.
► Groundwater salinity decreased from 2004 to 2010.
► Kriging methods are suitable methods for estimation of water quality.