## 1 Introduction  
In arid regions, groundwater represents one of the primary sources of water for agricultural and other development projects, especially in remote watersheds. Wadi Qena is located in the Eastern Desert of Egypt, draining toward the Nile valley. It is considered a promising area for agricultural and sustainable development projects. Wadi Qena is bound by the Nile River to the west and the Red Sea mountains series ridges to the East. The Wadi flows from north to south, unlike other major Egyptian Nile drainage systems, which are generally oriented from east to west [1]; the Wadi covers an area of 16,000 km\({}^{2}\) with an average width of 75 km [2]. Wadi Qena lies between latitudes 26\({}^{\circ}\)15\({}^{\prime}\)00\({}^{\prime}\) N and 28\({}^{\circ}\)15\({}^{\prime}\)00\({}^{\prime}\) N and between longitudes 32\({}^{\circ}\)15\({}^{\prime}\)00\({}^{\prime}\) E and 33\({}^{\circ}\)30\({}^{\prime}\)33\({}^{\prime\prime}\) E (Figure 1). It is easily accessible through a road network, connecting the densely populated Nile Valley with the touristic Red Sea Province. Wadi Qena receives 1.4 \(\times\) 10\({}^{8}\) m\({}^{3}\) annual precipitation, which feeds the aquifers [3]. In addition, it has mostly flatlands that are suitable for land development in downstream regions. Climatic data reveals that the maximum relative humidity varies from 53% in winter to 29% in summer. The average maximum temperature is approximately 23 \({}^{\circ}\)C in winter and 44 \({}^{\circ}\)C in summer, whereas the minimum is approximately 10 \({}^{\circ}\)C in winter and 22 \({}^{\circ}\)C in summer [4]. The average maximum recorded evaporation rate is 17.63 mm during June, whereas the average minimum recorded evaporation rate is 4.54 mm in December (Egyptian Meteorological Department 1935-2000). In the past decade, Wadi Qena has experienced rapid development, primarily related to agricultural projects that resulted in increased demand for groundwater resources. These groundwaters are exploited from three main aquifers: the Nubian Sandstone aquifer (NSA), the Post-Nubian carbonate aquifer (PNA), and the alluvial Quaternary aquifer [5,6]. Understanding the main processes controlling groundwater chemistry and recharge is important for sustainable management of groundwater resources used in this arid watershed. In this respect, gathering information related to recharge mechanisms, geochemical characteristics, and groundwater evolution is necessary for sustainable groundwater use [7, 8, 9]. Variations in groundwater geochemistry within the aquifers result from salt leaching in the aquifer matrix, cation exchange processes, and the length of time the groundwater remains in the aquifer [10]. However, local geology, the degree of rock weathering, the quality of recharge water, and inputs from sources other than rock-water interaction can influence groundwater chemistry throughout its flow path [11, 12, 13]. Moreover, accurately identifying the groundwater recharge mechanism and its sources using conventional hydrogeological methods is difficult [7,8,14]. In arid regions, integrating these methods with geochemical and environmental isotopic tracers can be utilized to understand the geochemistry of the groundwater, recharge sources, and to determine evolutionary processes [9,15]. It can also provide relevant information regarding the origin of groundwater mineralization [16]. Geochemical indicators and environmental isotopes offer unique and valuable insights regarding the origin of groundwater and its movements. They can also be used to effectively characterize tracing of contaminants and solute transport in groundwater [17]. They allow quantitative evaluation of mixing and other physical processes such as evaporation and isotopic exchange in hydrogeologic systems [18]. These integrations have been applied in many arid areas, including Australia, China, Tunisia, Saudi Arabia, and Egypt [15, 16, 17, 19, 20, 21, 22].