Groundwater contamination by nitrates in the city of Konya, (Turkey): A GIS perspective

Groundwater is an essential drinking water source in the city of Konya, Turkey. Approximately 75% of the city's water consumption has been supplied from 198 groundwater wells for the last six years. Nitrate (NO3−) is one of the important water quality parameters and was measured in the water samples taken from 139 wells in 1998 and from 156 wells in 2001 within the study area of 427.5 km2.To evaluate the nitrate data, a vector-based GIS software package ArcView GIS 3.2 was used. A hardcopy map of the city was digitized in the UTM projection system. The locations of the wells were obtained by a hand-held Global Positioning System (GPS) receiver.According to the maps produced, nitrate concentrations generally tend to increase in the city center, the average concentrations being 2.2 and 16.1 mg/L for the years of 1998 and 2001, respectively. A statistical correlation procedure was also applied to well depths and nitrate concentrations. As a result, correlation coefficients of 0.259 and 0.261 were obtained for data collected in 1998 and 2001. It is concluded that the distribution of nitrate concentrations is not correlated with well depths within the study area.