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In this study, intrinsic groundwater vulnerability for the shallow aquifer in northeastern Missan governorate, south of Iraq is evaluated using commonly used DRASTIC model in framework of GIS environment. Preparation of DRASTIC parameters is attained through gathering data from different sources including field survey, geological and meteorological data, a digital elevation model DEM of the study area, archival database, and published research. The different data used to build DRASTIC model are arranged in a geospatial database using spatial analyst extension of ArcGIS 10.2 software. The obtained results related to the vulnerability to general contaminants show that the study area is characterized by two vulnerability zones: low and moderate. Ninety-four percentage (94 %) of the study area has a low class of groundwater vulnerability to contamination, whereas a total of (6 %) of the study area has moderate vulnerability. The pesticides DRASTIC index map shows that the study area is also characterized by two zones of vulnerability: low and moderate. The DRASTIC map of this version clearly shows that small percentage (13 %) of the study area has low vulnerability to contamination, and most parts have moderate vulnerability (about 87 %). The final results indicate that the aquifer system in the interested area is relatively protected from contamination on the groundwater surface. To mitigate the contamination risks in the moderate vulnerability zones, a protective measure must be put before exploiting the aquifer and before comprehensive agricultural activities begin in the area.

This study focus on determining the groundwater availability zones in an arid region, Iraq using bivariate frequency ratio and combining frequency ratio and index of entropy approaches linked with remote sensing and GIS techniques. For building models, an inventory of boreholes with high flow rate (8 l/s) was firstly prepared and divided into two sets training and testing along with different groundwater occurrence factors. Selection of the factors was based on availability of data, literature review, and expert opinion. The selected factors were elevation, slope angle, curvature, aspect, topographic wetness index, stream power index, geology, soil, land use/land cover, and distance to faults. The statistical relationships between groundwater occurrence factors and geographic borehole locations were investigated using likelihood ratio. The linear combination technique was first used to derive groundwater availability zones with assumption that all groundwater factors have the same influence on the groundwater availability. In the second model, the weight for each groundwater factor was calculated using index of entropy method, and thus a weighted linear combination technique was used to derive groundwater availability zones. The final groundwater availability index produced by applying both methods were classified into five classes based on Jenks classification scheme: very low, low, moderate, high, and very high. The areas covered by very low to low groundwater availability zones occupy 70 and 72 % from the total area for frequency ratio and combining frequency ratio and index of entropy models, respectively, indicating that the groundwater availability condition is low. Validation of the prospecting maps using relative operating characteristic curves indicated that the prediction rates for frequency ratio model and combining frequency ratio-index of entropy model were 0.804 and 0.806, respectively implying that the combining frequency ratio-index of entropy model was slightly better than frequency ratio model alone.