Groundwater Flow Modelling of Semi-Arid Watershed Affected by Over-Exploitation: a Case Study of Lake Tuz (Salt Lake) Basin, Turkey

As the largest scaled spatiotemporal groundwater modelling study in Turkey, the aim of this paper was to model the groundwater flow of the Lake Tuz Basin (29 425 km2, Central Anatolia, Turkey), in which an over-exploitation (excessive usage) has been applied by pumping wells for years, to estimate its hazardous effects on the groundwater level. MODFLOW was used for modelling the groundwater flow of the watershed under transient conditions. GMS groundwater simulator was utilized to create the input files for MODFLOW. The model was yearly simulated for 24 years from 2000 to 2023. Model calibration and validation were performed by using groundwater observation data (water levels) of 2000–2015 and 2016–2023, respectively. The groundwater parameters were calibrated by the modified Clonal Selection Algorithm (a class of Artificial Immune Systems) linked with MODFLOW in MATLAB. Recharge was calibrated based on the land use/cover (30 different types) while other parameters (storage coefficient, hydraulic conductivity) were calibrated depending on the aquifer lithology (23 aquifers). Moreover, the groundwater flow model was run according to different scenarios to predict groundwater level changes under possible future conditions. The results showed that the model was successful in simulating the groundwater levels/heads and was enlightening to forecast their future changes in the Lake Tuz watershed.