The Province of Kirka (Eskisehir, Turkey), located in the catchment of the Seydisuyu Plain, has one of the largest Na-borate deposits in the world. However, boron concentrations in surface and ground waters downstream of Kirka Province, the Seyitgazi Plain, have increased over the past twenty years. Seyitgazi plain has been widely irrigated from groundwater and Seydisuyu River. In this respect, quality of the river water directly affects groundwater quality in the Seyitgazi Plain since river water is the main supplier for irrigation water in the Seyitgazi plain in addition to groundwater which is extracted from the wells drilled in the Seyitgazi Plain. Thus, any mining activity built in the catchment area of groundwater poses potential risk for the quality of groundwater in the discharge area.
The Seydisuyu River is fed from Catoren and Kunduzlar dam reservoirs which are located in the upper reaches of the Seyitgazi Plain. Chemical analysis of surface waters (n = 102) and groundwaters (n = 136) showed that boron concentrations in groundwater of the Seyitgazi Plain increased up to three to four times due to infiltration into the shallow aquifer system because the Seydisuyu River water is used for irrigation. Statistically, significant positive correlations were found between boron and arsenic due to deposition in the same playa lake. Since the boron bearing layers can contain arsenic minerals, arsenic can act in a tracer role for surplus boron concentrations in groundwater. Besides natural contribution, mining activities caused a substantial increase in boron and arsenic concentrations in the groundwater of the Seyitgazi Plain.