Spatial Modeling of Potential Zones for Groundwater and Their Spatial Overlap with Used and Covered Land in Western Basrah Province Using AHP and ArcGIS

Abstract

Given the worsening scarcity and pollution of surface water, particularly in southern Iraq's Basrah Governorate, with its arid desert environment and scarce rainfall, the importance of utilizing groundwater, especially for agricultural and domestic uses, becomes evident. In order to make optimal use of groundwater, decision-makers should be provided with systematic scientific studies on this water resource so that it can be managed properly. The Analytic Hierarchy Process method (AHP) was utilized to find groundwater potential zones (GWPZ), as well as the (ArcGIS Pro) software environment with addition to remote sensing. The area for this study was located in Basrah in southern Iraq, and it covered an area of 132.662 km2. Thematic layers were essential to the study and five of them were used according to their importance in the previously mentioned area, and they are: groundwater’s depth, LULC, slope, drainage density and rainfall. These parameters results were identified to create a map of potential groundwater locations for the study, and this was done through the use of a pairwise comparison matrix. The consistency ratio analysis (CR) illustrated that the previous inferred results are reliable and suitable to map zones where groundwater could potentially be found, as it was shown to be 0.022. Additionally, these same findings identified that the groundwater’s depth was the most influential parameter, as it had a relative weight of 0.4875, after which comes the LULC parameter which has weight of relatively 0.2277, whereas the lowest recorded weight was the of rainfall’s as it had a value of only 0.0556 due to the low rainfall and limited spatial variation in the region. The results, after dividing the map into five categories, showed that approximately one third of the specified area for the study (30.61%) had high groundwater potential zones. On the other hand, zones with potentially very high and medium amount of groundwater covered 26.56% and 17.23% of the area. Meanwhile, zones with potentially low and very low groundwater covered only 17.43% and 8.17%, respectively. To confirm the accuracy of the study model, field validation was conducted using 10 well sites, revealing an 80% accuracy rate. Statistical analysis of the study results revealed a strong positive correlation between agriculture and grasses practices and groundwater potential zones. These two activities are usually found together at a high percentage in zones with very high and high potential for groundwater, measuring 97.31% and 85.25% In contrast, the results of the statistical analysis showed an inverse relationship between barren land and the potential of groundwater. As for the urban area, the results revealed that it peaks in areas of medium potential and recedes in areas of very high potential. The study concluded by proposing 26 future well-drilling sites in high and very high potential areas, which provides a means to help decision-makers manage groundwater in the best way and achieve the desired development.