Creating a Drinking Water Quality Index (WQI) Map Using the Geographic Information System (GIS) Technique for Karbala City, Iraq

The geographic information system (GIS) technique is applied in the present study to produce a drinking water quality index map for the Karbala city in Iraq. Ninety-two samples of groundwater were collected from different sites in the study area and analyzed in terms of different chemical parameters affecting the quality of drinking water. The piper diagram is used to estimate the chemical type of groundwater in the study area. Na^+-SO_4^-2 and, Na^+-Cl^- facies were found to be the dominant major groundwater types. At few locations, the groundwater chemistry belongs to mixed Mg^2+-Ca^2+-SO_4^-2 and mixed Mg^2+-Ca^2+- Cl^- facies. Cations and anions were used to create a water quality database in the study area using (GIS) for the purpose of producing a spatial distribution map for each parameter using the Reverse Interpolation Technique (IDW). The results of these determinants were also used to calculate the values of the water quality index and the production of the index map of the quality of drinking water. The analysis of the WQI map results shows that only 1 % of the water samples fall within class II which represents good water quality and 57 % of the available well samples fall under class III which indicates poor water quality, 21% of the water samples fall in class IV which indicates a very poor water quality, and 20 % of the samples indicate unsuitable water. Wilcox and United State Salinity Laboratory (USSL) diagrams are also applied in the current study to evaluate the available water wells in the area, and to determine its suitability for irrigation purposes. To achieve this goal the Electrical Conductivity (EC) has been measured and the sodium percentage (Na %) and sodium Adsorption Ratio (SAR) have been calculated based on the chemical analysis of Ca^22+, Mg^2+, Na^+, K^+. The results s how that only 4 % of the water samples fall under the good to permissible category, and are suitable for irrigation.