Detection of Potential Zones of Groundwater for Different Valleys in Western Desert Using GIS

Abstract

In arid and semi-arid regions (ASARs) around the world, the investigation of groundwater potential zones has been a main target to recompense the massive shortage in rainfall and surface water supplies that occurs due to the climate changes and the increasing demand for agricultural and urbanization development. Several methodologies and criteria have been applied and developed by many researchers to identify appropriate sites and mechanisms to detect groundwater potential areas. The primary purpose of this study is to a develop a method to determine groundwater potential zones (GWPZs) in ASARs by examining an inventory of the primary methods and criteria that developed during the last few years. Recently, the combination of Remote Sensing (RS) and Geographical Information System (GIS) techniques can be used to overcome water scarcity problems and help in providing water requirements for population, agricultural and commercial purposes in the Iraqi Western Desert. Two study areas were considered to conduct this study, the first was Al-Mohammedi Valley basin which includes the required boreholes to validate the model and then the same methodology were applied in the second study area of Al-Ghadaf Basin. Various thematic layers such as geology, geomorphology, slope, soil infiltration, land use and land cover, rainfall, drainage density, and lineament density were derived from the RS data such as Landsat 8 satellite images, Digital Elevation Model (DEM) from Shuttle Radar Topography Mission (SRTM) and Iraqi geological maps. The output map of the GWPZs was generated by integrating all the thematic layers based on weighted values that were generated depending on the Analytical Hierarchal Process (AHP) approach. Accordingly, around 18.3 % and 23.27 % of the total precipitated water (47.4 × 106 m3 /year and 240.4 × 106 m3 /year) are infiltrated downward to recharge groundwater in Al-Mohammedi and Al- II Ghadaf basins respectively, while the residual percentage converts to surface runoff or lost through evapo-transpiration. Finally, the prospective map was examined and validated with the existing yield wells data within Al Mohammedi basin. Twenty two of twenty-eight validated boreholes match with the predicted classes of the yield boreholes and the value of the cross correlation confirms this finding as R2 value was 0.6