GIS-Based Evaluation of Groundwater Quality and Suitability in Dakhla Oases, Egypt

Abstract

Groundwater is the main source for agricultural and domestic purposes in the Western Desert of Egypt. Groundwater quality is significantly influenced by the surrounding anthropogenic activities. This paper is one of the attempts to spatially assess groundwater quality and its suitability for drinking and irrigation in Dakhla Oases using Water Quality Index (WQI) and GIS techniques. Calibrated Landsat 8 OLI satellite images were processed to produce Land Use Cover map (LULC) to assess the agricultural and human activities in the study area. Further, eight groundwater quality parameters and WQI were attributed to a GIS layer for 71 investigated wells for mapping purposes using the Inverse Distance Weighting (IDW) method in ArcGIS. LULC map showed that 75% of the study area is a bare land and 25% is urban and agricultural areas. Almost all the studied wells recorded total dissolved solids and sulfate coinciding with the Egyptian permissible limits for drinking purposes. Fe and Mn levels exceeded the allowable limits for drinking in the majority of Dakhla wells. Based on the WQI, 38% and 36.6% of the study area fell within the poor water category according to the Egyptian and WHO standards, respectively. Most of the groundwater wells were of the best quality for irrigation with regard to salinity (less than 2000 mg/L) and the excellent quality in terms of sodium absorption ratio (< 10). It can be concluded that GIS analyses of groundwater quality and suitability can provide one of the necessary inputs for management and planning of Dakhla Oases and other similar regions.