Hydrogeological investigation of Dinar (Afyonkarahisar) basin

In this study, Dinar (Afyonkarahisar) Basin was evaluated in terms of hydrogeology, hydrology and hydrogeochemistry. The basin is a sub-basin of Büyük Menderes River basin. The river is the most important surface flow of the basin. The river is born in the basin with the name of Dinar Stream and forms the beginning of the river. The river flows through Dinar Plain from southeast to northwest and flows into Işıklı Lake. Therefore, Dinar basin has the characteristic of a semi-closed basin. Allochthonous, autochthonous, paraallochthonous units and cover rocks are distributed in the basin. Units consisting of limestone and mélange are the basement rocks of the basin. Current sediments and limestones are the most important groundwater reserves of the basin. There are natural spring waters with natural discharge in the basin. Groundwater analyses were performed to determine its quality and pollution characteristics. Groundwater has physical characteristics such as "cold-slightly warm", "acidic", "quite hardhard" and "fresh-bitter" waters. Chemically, Ca2+ and HCO3 -ions are dominant in groundwater. According to Piper and chadha diagrams, groundwater is in the "CaMgHCO3" water facies. Groundwater in the basin complies with TS-266 (2005) and WHO (2011) drinking water standards in terms of physical and chemical parameters. Different irrigation water quality index parameters were calculated. Groundwater is suitable in terms of irrigation water quality. When the effect of agricultural activities on groundwater is considered, there is no pollution element in groundwater in terms of nitrite and ammonium. However, nitrate content exceeded the nitrate concentration limit value (50 mg/l) of WHO (2011) and TS-266 (2005) drinking water standards in 7 different points where agricultural activities and fertilization are intensive. In addition, no trace element pollution was encountered in the basin. Manganese (Mn) concentration value was determined to be above the TS-266 (2005) drinking water standard limit value (0.05 mg/l) in 2 water samples. The manganese increase indicates that the water in shallow wells interacts with rocks and the well water may be affected by agricultural activities. Keywords: Groundwater, hydrogeology, hydrochemistry, Dinar basin