Environmental Earth Sciences (2020) 79:145 https://doi.org/10.1007/s12665-020-8823-x ORIGINAL ARTICLE Assessment of groundwater quality in Bahariya Oasis, Western Desert, Egypt Abbas M. Sharaky1 · Suad H. Abdoun2 Received: 22 April 2019 / Accepted: 21 January 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020 Abstract Groundwater quality and the overall rate of abstraction from the Nubian sandstone aquifer system in the Bahariya Oasis was assessed to determine whether the resource was of a suitable quality for its current use and that that the current usage is sustainable. The hydrochemical analysis of 84 representative groundwater wells was carried out to determine the main hydrochemical characters, genesis and evaluation of the groundwater quality for diferent uses. The physical and chemical characteristics were measured for the groundwater according to standard methods, such as temperature, electrical conductivity (EC), total dissolved solids (TDS), pH, major anions and cations, and heavy metals such as iron, manganese and zinc. The average values of the EC, TDS, pH, major cations and anions did not exceed the recommended limits for drinking water set by the World Health Organization (WHO). Most of the three aquifer zones contain freshwater with an average TDS content of 286 mg/l. Manganese concentrations exceed the recommended WHO drinking water limit. Keywords Bahariya Oasis · Groundwater · Nubian sandstone · Water quality · Salinity · Water pollution · Aquifer Introduction The groundwater resources in Bahariya Oasis are asso- ciated with the main Nubian Sandstone Aquifer System Groundwater is an important natural resource and is gener- (NSAS) that is one of the largest and most important trans- ally the main source of water in desert areas. More than 95% boundary aquifer systems in Northern Africa. It is composed of the Egyptian territories are deserts. The present culti- mainly of continental sandstones with shale and clay inter- vated areas in Egypt do not have the potential to provide the calations. The aquifer has a saturated thickness that varies required food for the growing human population. Therefore, between 100 and 1500 m (Masoud and El Osta 2016). The groundwater abstraction needs to be increased in the region NSAS is shared by Egypt, Libya, Sudan and Chad, a total to reclaim desert land. area of about 2.2 million km2. The NSAS covers an area of An example of this is taking place is in the Bahariya 826,000 km2 in Egypt (38% of the total area), 760,000 km2 Oasis, which is one of the Egyptian oases that mainly (34% of the total area) in Libya, 376,000 km2 in Sudan (17% depend on groundwater for all purposes. The groundwater of the total area) and 235,000 km2 in Chad (11% of the total aquifers in Bahariya are divided into three horizontal zones: area) (Ahmed 2013; Ahmed et al. 2013). the lower zone (S1); the middle zone (S2); and the upper zone (S3) which are separated by clay and shale units. The study problem Egypt has planned to reclaim 4 million acres over the next few years commencing in 2016. The present stage of the * Abbas M. Sharaky program is to cultivate 1.5 million acres depending mostly [email protected] (90%) on non-renewable groundwater pumped from the Suad H. Abdoun Nubian Sandstone Aquifer in the Western Desert. About [email protected] 20,000 acres of the 1.5 million acre project is located in Bahariya Oasis. The only source of water in this region is the 1 Department of Natural Resources, Faculty of High African Studies, Cairo University, Cairo, Egypt groundwater available for cultivation and domestic uses from the Bahariya Oasis. As a result of increasing population and 2 Ministry of Water Resources and Irrigation, Cairo, Egypt Vol.:(0123456789)1 3 145 Page 2 of 14 Environmental Earth Sciences (2020) 79:145 cultivated areas, deep well drilling was initiated in 1963. and runs westward to join the asphaltic road at 45 km to the This produced declines in the piezometric head of the aqui- north of El-Gedida iron ore mine. fer during the period 1963–1970 at an annual rate of about 1.2 m (Masoud and El Osta 2016). Literature review Objectives of the study The NSAS has been subjected to numerous studies since the beginning of the twentieth century starting with Ball (1927) The main purpose of the present paper is to re-evaluate the and Sandford (1935) in the frst half of the century to more hydrogeological conditions of the groundwater occurrence recent studies by Thorweihe (1990) and Heinl and Thor- in Bahariya Oasis to investigate the efects of water exploita- weihe (1993). The recent studies include CEDARE (2002) tion on both water levels and water quality in the aquifer as that developed a regional groundwater fow model for the well as its suitability for drinking, domestic purposes and for NSAS that had its northern boundaries set at the shoreline irrigation. The study also aims to analyze the physical and of the Mediterranean Sea (Ebraheem et al. 2002; Sefelnasr chemical parameters such as temperature, electrical conduc- 2002; Thorweihe and Heinl 2002; Salem and Pallas 2004; tivity (EC), total suspended solids (TSS) and total dissolved Bakhbakhi 2006; Khalifa 2006; Sawires 2010; Tanner and solids (TDS), pH value, major anions and cations and some Khalifa 2010; El Kashouty et al. 2012; Hamdan 2012; Ham- heavy metals such as iron and zinc. dan et al. 2012; Ahmed 2013; Ahmed et al. 2013; El Hossary 2013; Abd El All et al. 2015; Masoud and El Osta 2016; Location of Bahariya Oasis Rabeh et al. 2018; Sharaky et al. 2018). The studies concluded that groundwater in the NSAS Bahariya Oasis is a natural large pear-shaped depression in has a pluvial origin with recharge having taken place dur- the central part in the Western Desert of Egypt. It covers an ing frequent wet periods. The groundwater in the study approximate area of 2078 km2. It is located between latitudes area has fowed mainly from hills in western Sudan many 27° 46′ 27″ and 28° 30′ 32″ N and longitudes 28° 29′ 22″ thousands of years ago. The NSAS is mainly composed of and 29° 08′ 35″ E (Fig. 1). The study area is connected to two water-bearing sequences of sediments. The frst one is the Nile Valley by two main roads. The frst is a 350 km-long the water-bearing sequence contained in the Nubian facies NE–SW asphaltic road that connects Giza town with Bawiti series, while the second one is the water-bearing sequence (the oasis capital). The second main road is the motor track, contained in the post-Nubian rocks. which starts at Samalut in the Nile Valley around 175 km Although several studies of the hydrogeological charac- teristics of the NSAS have been carried out, detailed and accurate information about how this aquifer system func- tions is limited. This includes the current limited information about the total volume of water stored in the aquifer system, the rate of groundwater fow, and total annual extraction. The groundwater quality of the NSAS ranges from fresh- water to saline. The water salinity changes from freshwa- ter (less than 1000 mg/l) in the southern part of the system to brackish water (1000–10,000 mg/l), and saline water (10,000–35,000 mg/l) in the northern part. The NSAS is composed of diferent water-bearing strata that are laterally or vertically interconnected (CEDARE 2002). It can be diferentiated locally into two major aquifer systems (Bakhbakhi 2006). The frst one is the oldest and the most extensive aquifer is known as the Nubian Aquifer System (NAS). It underlies the Post-Nubian Aquifer Sys- tem (PNAS) and only occurs north of the 25th latitude, and overlies the NAS in the northern part of the Western Desert of Egypt and in northeastern Libya (CEDARE 2002). Low permeability aquicludes separate the two aquifers (Bakh- bakhi 2006). Fig. 1 Digital elevation model of Bahariya depression from Advanced Spaceborne Thermal Emission and Refection Radiometer In Egypt, sandstones of Cretaceous period underlie most (ASTER) resolution of 90 m showing isolated hills in the depression of the Western Desert including the New Valley, parts of and the outline escarpment. https ://gdex.cr.usgs.gov/gdex/ the Eastern Desert and Sinai. Crystalline basement rocks 1 3 Environmental Earth Sciences (2020) 79:145 Page 3 of 14 145 are dominant along the coastal zone of the Red Sea, and of the northern sector ranges from 80 to 140 m amsl, while on western margins and the most southern regions of the the southern sector ranges from 140 to 160 m amsl. The NSAS. These rocks include granites, granodiorites, diorites, elevation of the central sector ranges from 140 to 180 m gneisses, schists, and basalts (Klitzsch 1994). The basement amsl. The most important geomorphic features include the complex is overlain by a series of sands, sandstones, clays, plateau surface, bounding escarpments, oasis foor, residual and shales which are commonly termed the Nubian Sand- hills (questas), volcanic cones and sheets, valleys or wadis, stone Series that varies in thickness from tens of meters in alluvial fans and terraces, dry and wet sabkhas, sand sheets the northern regions of Sudan to about 250 m in the southern and sand dunes (Parsons 1962; Embabi and Mostafa 1979). localities of the Kharga Oasis, 900 m in northern Kharga, According to El Akkad and Issawi (1963), Said and and about 1800 m in the Bahariya Oasis. It attains a thick- Issawi (1964), CONOCO (1986) and Hamdan and Sawires ness of more than 3500 m in the northern localities of the (2011), the geologic succession in Bahariya area includes Dakhla Basin and over 4500 in the northwestern part (Her- Precambrian, Cambrian Cretaceous Paleocene Eocene Oli- mina 1990, Klitzsch and Wycisk 1999) of the Kufra Basin gocene and Quaternary rocks.