ABSTRACT: This study includes hydrogeological and hydrogeochemical assessment and investigation of the flow andcontamination relationships between surface water and groundwater of the Lake Bafa and its western part.Menderes Massif rocks form the basis of the geological structure in and around the study area. Jurassic-Cretaceousmarbles belonging to the Menderes Massif, overlying Neogene lacustrine carbonates and Quaternary alluviumare the aquifer forming units. Groundwater is exploited from many wells and springs. Lake Bafa and geothermalfluid with conductivity values of 23400 and 56000 µS/cm are Na-Cl dominated waters, respectively. Seawater mixing percentages have been calculated for saline waters. Lake Bafa is recharged by geothermal water affected by seawater intrusion, rainwaters and Büyük Menderes River. Low-temperature saline karstic waters supplied from the marbles belonging to the Menderes Massif in the northwest of the Lake Bafa are used by fish farmers in the region.Groundwater with about t 2 m3 /sec  is discharged to  the Lake Bafa or Büyük Menderes River after usage  Processes,which determine the chemistry of the lake, are mixture of these water and effect of evaporation.The seawaterintrusion is controlled by the Akköy Fault extending from the sea to the Lake Bafa.Salinity of the Lake Bafa is not asign of contamination, but the result of natural geological evolution.However, geothermal waters containing highdissolved ions discharged in to the Lake Bafa negatively affect the ecosystem of the lake. Geothermal waste watershould be removed from ammonium and reinjected in to the marble unit. This implementation has been determined asthe most suitable method for the continuity of the reservoir and ecosystem. The suitability of the waters for drinking,livestock and fish farming has been examined. The surface water and groundwater relationship is determined in andaround of the Lake Bafa, and the results are interpreted by evaluating organic-inorganic chemical analysis. Solutionsuggestions for sustainable water resource management of the Lake Bafa are presented in detail.