Evaluation of groundwater vulnerability in El-Bahariya Oasis, Western Desert, Egypt, using modelling and GIS techniques: A case study

Abstract

The Nubian Sandstone Aquifer (NSSA) is the main groundwater resource of the El-Bahariya Oasis, which is located in the middle of the Western Desert of Egypt. This aquifer is composed mainly of continental clastic sediments of sandstone with shale and clay intercalations of saturated thickness ranging between 100 and 1500 m. Vulnerability assessment to delineate areas that are more susceptible to contamination from anthropogenic sources has become an important element for sustainable resources management and land use planning. Accordingly, this research aims to estimate the vulnerability of NSSA by applying the DRASTIC model as well as utilising sensitivity analyses to evaluate the relative importance of the model parameters for aquifer vulnerability in the study area. The main objective is to demonstrate the combined use of the DRASTIC and the GIS techniques as an effective method for groundwater pollution risk assessment, and mapping the areas that are prone to deterioration of groundwater quality and quantity. Based on DRASTIC index (DI) values, a groundwater vulnerability map was produced using the GIS. The aquifer analysis in the study area highlighted the following key points: the northeastern and western parts of the NSSA were dominated by 'High' vulnerability classes while the northwestern and southeastern parts were characterised by 'Medium' vulnerability classes. The elevated central part of the study area displayed 'Low' aquifer vulnerability. The vulnerability map shows a relatively greater risk imposed on the northeastern part of the NSSA due to the larger pollution potential of intensive vegetable cultivation. Depth-to-water, topography and hydraulic conductivity parameters were found to be more effective in assessing aquifer vulnerability.

Estimation and Mapping of the Transmissivity of the Nubian Sandstone Aquifer in the Kharga Oasis, Egypt

“…Hamdam et al [16] reported transmissivity values between 236 m 2 /d and 3045 m 2 /d as a result of 12 pumping tests conducted in the Nubian sandstone aquifer in the El-Bahariya oasis, about 300 km northwest of the Kharga oasis. Masoud and Osta [17] analyzed 26 pumping tests in the Nubian sandstone aquifer of the El-Bahariya oasis and reported transmissivity values between 191 m 2 /d and 970 m 2 /d; the discrepancy with the previous study was not explained.…”

Quantitative Assessment of Desertification in Bahariya Oasis Environment, Western Desert, Egypt

“…Other geological formations include El-Heiz formation, El-Hefhuf formation, and Quaternary deposits (El-Sisi et al, 2002;Khalifa et al, 2006). The Bahariya Oasis, initially developed during the lower Eocene due to tectonic movements which is now occupied by a major depression floor dotted by several isolated residual hills and is surrounded by escarpments from the northern and eastern parts (Hamdan 2012;Masoud and El-Osta, 2016) (Fig. 2b).…”

“…The main water resource for irrigating the reclaimed areas ( Fig. 2d) in this Oasis is groundwater stored within the Nubian Sandstone Aquifer (NSSA) (Masoud and El-Osta, 2016). Groundwater is susceptible to anthropogenic activity resulting from urbanisation, increase in populations, land reclamation, increase of agricultural activities and lack of proper sewage and irrigation drainage systems (El-Sisi et al, 2002).…”

“…The digital elevation model (DEM) and major geomorphological map of the Baharyia Oasis were previously produced by and Elnaggar 2017and Masoud and El-Osta (2016), respectively ( Fig. 2a & b).…”

GIS-based bivariate statistical techniques for groundwater potential analysis (an example of Iran)

“…In the view of these weaknesses, there is a strong requirement for reassessment of groundwater resources using pioneer technology such as Geographic Information System (GIS), Global Positioning System (GPS), and Remote Sensing (RS) (Srivastava et al 2013;Singh et al 2014). The growth of these tools has also prepared another time and cost impressive means of groundwater potential analysis (Nampak et al 2014;Masoud and El Osta 2016). So, according to Davoodi Moghaddam et al (2015), groundwater potential analysis can be very useful and helpful for managers to prepare best management scenarios of water resources in any region.…”