The use of the pilot points method on groundwater modelling for a degraded aquifer with limited field data: The case of Lake Karla aquifer

Groundwater depletion poses a major threat to global groundwater resources with increasing trends due to natural and anthropogenic activities. This study presents a surface-groundwater framework for water resources modelling of ill-posed problems in hydrogeologically data-scarce areas. The proposed framework is based on the application of a conceptual water balance model and composed of surface hydrological (UTHBAL) and groundwater flow simulation with the integration of a Newton formulation of the MODFLOW-2005 code (MODFLOW-NWT) and PEST suite modules. The groundwater simulation includes a preprocessor tool for automated calibration and a post-processor tool for automated validation. The methodology was applied to a rural region of Central Greece, Lake Karla Basin, which is degraded due to groundwater resources overexploitation to cover irrigation water demands. The aquifer is modelled focusing on a precise simulation-validation procedure of the conceptual model. The groundwater model was calibrated with the calibration preprocessor tool for spatially distributed hydraulic conductivity with the pilot points method. The calibration process achieved satisfactory results as validated by the post-process analysis of observed and simulated water levels. The findings for the groundwater budget indicate that the groundwater system is still under intense pressure even though farming activity in recent years has turned to less water-intensive crops. © 2021 The Authors Water Supply