This study examines the effects of rapidly increasing industrial activities on groundwater levels in the Trakya Region of Turkey where groundwater is the main resource for industrial, agricultural, and domestic water supply. The Ergene River Basin (11,325 km 2) is the most important catchment, around half of which is underlain by the unconfined 600 m thick Corlu/Ergene aquifer of Miocene/Pliocene age. Using water-table monitoring data from 13 monitoring wells the relation between potential pumping and water table fluctuation was evaluated. The average aquifer reserve and the total discharge of the area per year were determined as 340 and 460 Mm(3) respectively. The annual recharge was calculated as 123 Mm(3). The results show that the total amount of discharge (outflow + withdrawal) is much higher than the groundwater recharge, i.e. the system is not sustainable.