| Title | Hydrogeochemical Properties of Geothermal Fluid and its Effect on The Environment In Gediz Graben, Western Turkey |
|---|---|
| Authors | Alper BABA, Celalettin SIMSEK, Orhan GUNDUZ, Alper ELCI, Alim MURATHAN |
| Year | 2015 |
| Conference | World Geothermal Congress |
| Keywords | Geothermal energy, arsenic, boron, Gediz graben, Turkey |
| Abstract | In parallel to developing geothermal energy applications such as electricity generation and direct application in different part of Turkey, many sites experience environmental problems such as groundwater and surface water contamination. At present 2084 MWt is actually being utilized for direct applications and 243.35 MWe of electricity is being generated in Turkey. Most of this energy originates from the Menderes Massif (consisting of mica-schist, gneiss and marbles) which discharges along the rims of east–west-trending faults that form the Büyük Menderes, Küçük Menderes, Gediz, and Simav grabens in western Turkey. With a length of 140 km and a width of 3–40 km, Gediz Graben is one of the most important geothermal sites for geothermal energy in western Anatolia. The graben has a WNW–ESE trending structure bounded by two major active normal fault systems. Many geothermal fields occur along Gediz Graben from Alaºehir to Turgutlu districts. Within this region, geothermal energy is being actively used for green house and district heating as well as thermal tourism and balneology. More than 100 boreholes have been done for power generation in this graben during the last decade. The depth of these boreholes recently reached to 2954 m and the highest reservoir temperature (287 °C in 2750 m) ever achieved in Turkey was measured within this system. The geothermal fluid in Gediz Graben is mostly dominated by Na and HCO3 ions whereas groundwater is mostly dominated by Ca and HCO3 ions. The chemical analyses further revealed very high levels of heavy metals such as arsenic and boron reaching to values of 432 µg/L and 60 mg/L, respectively. The results also indicated that uncontrolled discharge of geothermal fluid influence the quality of surface and subsurface water resources of the region where these resources are commonly used for agricultural irrigation and domestic water supply. In particular, the levels of arsenic and boron in surface and subsurface waters exceeded the maximum allowable limits given in national and international standards for drinking-water quality. Thus, strict re-injection practices need to be implemented in Gediz Graben in order to prevent contamination of the already scarce water resources of the region. |