Assessment karstic water origin along South slope of Grate Caucasus Mountain range

The impact of climate change had caused that precipitation has significantly decreased in Georgia which caused significant decrease of surface water flows and depletion of groundwater amounts in natural springs. In the same time, the waters recharged in karstic aquifers, occurring on the southern slopes of the Greater Caucasus Mountains, can be considered as alternative groundwater resources for the communities in lowlands and the adjacent foothills. Here, about half of the renewable groundwater resources in artesian basins and confined groundwater systems in Georgia can be considered as belonging to the above mentioned water-bearing horizon. In order to assess water resources, the pathways between the recharge zones along the Caucasus and aquifers need to be addressed and risks of groundwater contamination along these pathways need to be evaluated.

On the territory of West Georgia, hydrogeological and hydrogeochemical surveys were performed in order to define the main hydrogeological features of the region. In the frame of this research, more than one hundred water sources (springs, wells, boreholes, rivers) were sampled during 2019. Physical parameters (pH, O₂, EC, temperature) were measured on site during sampling. Water samples were collected for chemical (major ions) and isotope analysis (¹⁸O and ²H). Karstic areas of West Georgia were covered by mapping. Isotopic composition of water in the study area evolves according to a line parallel with the global meteoric water line. Available isotopic data indicate several groups of groundwater types. Some of them very probably represent older waters, with substantially long mean residence time. Samples with pronounced isotope composition variability indicate the evolution of groundwater isotopic composition from the recharge area in the mountains through river valleys to the exfiltration areas. Deuterium excess shows higher values, typical for mountain precipitation and snow in mountain ranges. The conjunctive use of isotopic approaches demonstrates a high potential for future water resources studies in Georgia.