An investigation of the source of salinity in groundwater using stable isotope tracers and GIS: A case study of the Urmia Lake basin, Iran

Salinization of groundwater resources, especially in arid areas, limits their use. This problem can be aggravated by low annual precipitation, greater evaporation, and an excessive water discharge. The various sources of salinization, particularly in the unconfined aquifers, make it difficult to manage these resources. The sources of salinity can be detected through detailed sets of tracer data and a spatial analysis of their variation over the aquifer. Regarding the intense computational effort needed for this purpose, the geographic information system (GIS) can be used as a powerful tool for spatial analysis. This study aims to reveal the sources of salinity in the Azarshahr and Shabestar-Sufyan aquifers located in the Urmia basin, northwest Iran. The study is based on a comprehensive geochemical and stable water isotope (δ18O, δ2H) investigation of groundwater. We conclude the effectiveness of using isotope tracers to observe the effect of basin geology on water salinity. Evaporation and the dissolution of evaporative rocks in these regions is greatly effective in the isotopic concentrations. As is evident from a Piper diagram, in some parts of the study area, the main groundwater source is precipitation and there is no significant relationship between precipitation and the Urmia Lake. [Display omitted] •Variety of salinization sources, makes it difficult to manage these resources.•Salinity sources are detected through isotopic tracer data and spatial analysis of their variation over the aquifer.•Contour maps of ground water δ18O and δD values revealed their correlation with other chemical tracers.•Evaporation and dissolution of evaporative rocks in these regions control the isotopic concentrations.•Based on Piper diagram, the main groundwater origin is rainfall and its salinity isn’t highly impacted by Urmia Lake.