Seasonal and spatial variations in water quality of deep aquifer in the Harran plain, GAP project, southeastern Anatolia, Turkey

Groundwater is used for both drinking and irrigation purposes. Thus, its monitoring and understanding the processes controlling its quality are crucial in terms of sustainable use. Groundwater samples were collected from 11 deep aquifer wells located in the Harran plain, Southeastern Anatolia during four seasons and analyzed for TDS, EC, pH, Na + , K + , Ca 2+ , Mg 2+ , Cl − , F − , SO 4 2− , HCO 3 − , NO 3 − . Techniques such as ANOVA, correlation analyses, heat-mapping and Principal Component Analyses (PCA) were used to investigate main factors controlling seasonal and spatial variations in groundwater quality parameters. Grounwater quality parameters were also associated with topographical parameters [elevation, slope, flow direction, flow accumulation, and Topo Wetness Index (TWI)]. According to WHO standards, average values of all parameters investigated were in general within allowable limits for drinking water with a few exceptions for NO 3 − , SO 4 2− and F − that exceeded threshold limits at some locations. Seasonal variations in all water quality parameters except EC, TDS and SO 4 2− were statistically significant ( p