Spatio-temporal variations of groundwater quality index using geostatistical methods and GIS

A groundwater quality map serves as a deterrent mechanism that provides insight into likely environmental health predicaments. The objective of this study was to create map and evaluate the quality and changes in groundwater during the study period in Erbil, Iraq. Based on the 13 groundwater parameters, the water quality index (WQI) was calculated for 61 wells from 2015 to 2017 for wet and dry seasons. To generate WQI maps, two geostatistical analyst tools in Geographical Information Systems, including Kriging and Inverse Distance Weighted (IDW) were used. For determining the most suitable method, statistical indices were applied to the obtained data. The results showed that the Kriging method increases the prediction accuracy compared to the IDW method. The water quality in 2017 was decreased compared to the previous years and the WQI was increased from 1.64% to 11.47%. Untreated domestic and industrial wastewater causes groundwater pollution which was the main reason for the decrease in the water quality of Erbil city.