Turkey is the seventh richest country in the world in terms of geothermal potential (2705 MWt for direct use and 114.2 MWe for power production annually (Baba, 2012; 2013). The Aegean and Marmara regions show substantial potential for geothermal energy utilization (Faulds et al., 2009). The first geothermal research and investigations in Turkey were started by the General Directorate of Mineral Research and Exploration (MTA) in the 1960s. Since then 222 geothermal areas, 95% of which are low-and medium-enthalpy fields, widely used for direct heat applications, have been discovered by MTA (Mertog˘lu, 2010; Dag˘ıstan, 2012). Turkey has around 1000 natural thermal and mineralized springs and 527 wells. Their installed capacity is 4764 MWt (Dag˘ıstan, 2012; MTA, 2011). Geothermal areas in the western Turkey are located mainly along the major grabens such as Büyük Menderes, Gediz, and Küçük Menderes (Fig. 6.1). Geothermal fields in the study area are located within the Gediz graben (Fig. 6.2). Hydrogeological and hydrochemical characteristics of the thermo-mineral waters in the study area are described in this chapter. The study area is geographically divided into three main groups: Turgutlu, Salihli, and Alas¸ehir geothermal areas. The thermo-mineral waters are used for spa facilities, therapeutical purposes, and greenhouse and district heating applications. Additionally, several new deep wells have been drilled for power production.