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The Köprüören Basin, located in Kütahya Province (Western Türkiye), hosts long-standing silver mining operations centered in the Gümüşköy area, where a complex geological framework controls groundwater flow and the mobility of contaminants. The region comprises several stratigraphic units, including the Carboniferous–Permian Şahin Formation (phyllite, clay-schist, marble), the Permian–Triassic marbles of the Karaağaç Formation, the Middle–Upper Miocene dacitic–rhyolitic tuffites of the Tavşanlı Volcanics, the Lower Pliocene marls, sandstones, and tuffs of the Çokköy Formation, the Upper Pliocene limestone–dolomite alternations of the Emet Formation, and the Quaternary clastic sediments of the Bozyer Formation (Arık, 2002). Türkiye’s only silver deposit is developed within the basement rocks, Miocene volcanics, and Pliocene units, making the area of high economic importance. Modern mining activities in Gümüşköy began in 1987 with cyanide leaching, producing 122.4 tons of 99.9% pure silver annually, and ore production reached five million tons after 2009 (Sasmaz, 2011). While contributing to regional economic development, mining activities have generated significant environmental challenges in the basin. The collapse of one of the mine waste pools in 2011 caused the contaminated wastes to spread into surface-water systems. Geochemical investigations conducted in 2012 indicated that, in addition to natural geogenic sources, mining activities represented a major anthropogenic source of arsenic and other trace elements (Pb, Sb, Zn) through leakage from waste pools (Arslan & Çelik, 2015; Arslan, 2017). The hydrostratigraphic units of the basin were characterized in a recent study (Mohamed, 2025), analyzing the areal extent, thicknesses and hydraulic properties of the aquifers using data obtained from 68 wells. Accordingly, the most productive aquifer occurs within the limestone–marl alternations of the Upper Pliocene Emet Formation, with a thickness ranging from 12 to 223 m. Groundwater is abstracted from this aquifer for both irrigation and mining operations. Silver production consumes large amounts of water (1,713 m³ per ton of silver; Meißner, 2021), a substantial fraction of which is extracted from groundwater in the Köprüören Basin, further exacerbating pressure on local water resources. Recent declines in groundwater levels indicate that water use in the basin is unsustainable. Field reconnaissance in 2024 confirmed ongoing leakage from mine-waste pools, especially near drainage channels. Local reports of rising colon cancer cases suggest possible long-term exposure to trace elements. These findings highlight the continuing environmental and public-health risks and emphasize the need for monitoring, improved management, and sustainable water use in the Köprüören Basin.ReferencesArık, F., 2002. Geochemical Modeling of Gümüşköy (Kütahya) Silver Deposit, PhD Dissertation, Selçuk University, Türkiye.Arslan, Ş., 2017. Assessment of groundwater and soil quality in Köprüören Basin, J. African Earth Sci., 131, 1–13.Arslan, Ş., Çelik, M., 2015. Pollutants in soils and surface waters around Gümüşköy mine, Bull. Environ. Contam. Toxicol., 95(4), 499–506.Meißner, S., 2021. The Impact of Metal Mining on Global Water Stress and Regional Carrying Capacities—A GIS-Based Water Impact Assessment. Resources, 10(12), 120.Mohamed, A.S., 2025. Characterization of the Köprüören Basin Aquifer System, Master’s Thesis, Ankara University.Sasmaz, A., 2011. As, Ag, Pb, Sb and Tl Levels in Soil and Plants Around Gümüşköy Mining Area, TÜBİTAK Project CAYDAG-110Y003, Ankara.