Delineation of Groundwater Recharge Zones in Ali Al-Gharbi District, Southern Iraq Using Multi-criteria Decision-making Model and GIS

Abstract

This study identifies the groundwater recharge zone in an arid region of southern Iraq in a GIS framework using two multi-criteria decision-making techniques, namely the analytical hierarchy process (AHP) and the technique for order of preference by similarity to ideal solutions (TOPSIS). Eight factors are used to delineate groundwater recharge zones based on local conditions and data availability. These factors are elevation, slope, lithology, soil, land cover, drainage density, aquifer’s saturated thickness, and groundwater depths. These factors are prepared using different data sources, such as remotely sensed imagery, field survey, and borehole testing reports. AHP is mainly used to derive factor weights that reflect the contribution of each factor in the siting of the groundwater recharge project, while TOPSIS is used to rank the alternatives. The ranked values are classified into five groundwater recharge suitability zones: very low, low, moderate, high, and very high. The very low to low suitability classes cover an area of 75 km2 (12% of the study area), the high to very high classes encompass an area of 436 km2 (72%), and the moderate class extends over the remaining parts of the study area 99 km2 (16%). Results are validated using the receiver operating characteristic curve. This validation test revealed a prediction accuracy of 76% (good predictive model).