Assessment of Groundwater Quality Changes in the Rural Environment of the Hungarian Great Plain Based on Selected Water Quality Indicators

In the present study, changes in groundwater quality are assessed after the construction of the sewerage network, based on 3 water quality indices. Sampling took place before (2013) and after (2017, 2018, 2019) the establishment of a sewerage network in 2014. In the pre-sewerage period, strong pollution of the groundwater was detected. A total of 90% of the groundwater wells according to the water quality status by Brown, 70% of the wells according to the contamination index C d by Rapant, and 80% of the wells according to the Canadian Council of Ministers of the Environmental Water Quality Index were categorized in the “polluted” or “heavily polluted” categories. After the establishment of the sewerage, significant changes were observed. In 2017, the number of wells in category 5 indicating the most contaminated samples decreased significantly for all three indices, while the number of samples in categories “good” and “acceptable” increased. Discriminant analysis was performed to determine if pre- and post-sewerage samples could be separated. A total of 75.6% of the cross-validated values were successfully categorized into the appropriate category, which indicates a significant difference between pre- and post-sewerage. Based on point and interpolated maps, it was established that in 2013, all three indices showed the highest pollution in the inner and southern parts of the settlement, while the northern areas of the settlement were less polluted. Based on the indices, it was determined that the process of groundwater purification in the settlement has started, although it will continue for years to come.