Groundwater modeling and management in a complex lake-aquifer system

In this paper, the hydrogeologic analysis and the development of a numerical model for the simulation of a complex system of aquifers in Northern Greece are presented. The study area faces a severe environmental danger as the unsustainable water consuming practices have resulted in negative water balance and severe water shortage. Based on field data and in-situ measurements carried out by several research groups during the last 30 years, a conceptual model is developed, that alters what scientists believed to date as far as the hydraulic communication between the shallow and the deep aquifer, as well as the lake-aquifer interaction are concerned. Based on the assumptions of the conceptual model, a numerical model has been developed in order to investigate the regional groundwater flow in the aquifers. The Modflow program has been used for its implementation. The results have verified firstly that a marginal hydraulic contact between the 2 aquifers is permitted, and secondly that the assumed relation between the lake's water volume and the aquifer's water table fluctuations is practically negligible. The dramatic decrease in the lake's water reserves by 90%, as the model results show, is mainly due to the reversing of the torrent-aquifer interrelation. Finally, the model is used as a management tool for the restoration of the aquifer as well as of the lake.