Firat Ersoy, ArzuErsoy, Hakan2015-04-082015-04-082009Journal of Science and Technology 3 (2), 2009, 267 – 2841307-3818Approximately 10 different systems of classification of natural water types were developed (Matthess, 1982). Stuyfzand Classification System combines excellent features of existing classifications with new, strongly diagnostic criteria for subdivision. And this classification plays very important role for determination of hydrogeochemical evolution of groundwater plain. The location plain is important because of it has very huge amount of water in the Gümüşhacıköy Aquifer. This water is used for the industrial purposes and agricultural area in the plain. In this study hydrochemical evolution of Gümüşhacıköy Plain was determined using Stuyfzand Classification System and totally 79 well water, 37 well water analysis results between 1951 and 1972, and 42 well water analysis results between 2003 and 2004, were compared with each other considering this classification system. According to this classification system, the sequence concludes that freshening is going on from NaHCO3+ to MgHCO3+. The south and southwest of the plain is formed CaHCO3f water type according to the first analyses results but CaHCO3+ water type dominates the consequence of freshening to the second analyses results. Typical freshening is going on from west to east in time and the composition of the groundwater is turned into CaHCO3+ water type.enStuyfzand Classification SystemHydrogeochemistryGümüşhacıköy AquiferArticle