In developing countries, increasing population constitutes a big problem because of its great effects on the national growth leading to the increase in poverty and social problems. The acquisition of new land for agriculture remains as one of the major solutions to minimize such harmful effects. In Egypt, there is a continuous demand for more water necessary for reclamation of new land to be added to the existing cultivated land, so the development of groundwater resources in Egypt has received special attention a few years ago where the groundwater aquifers underlying the Nile Valley, the Delta, parts of the deserts and coastal area act as an auxiliary source of water in Egypt. Therefore, nowadays, the Egyptian Government and the private sector are interested in developing the desert zone outside the flood plain of the Nile River and targeting the reclamation of about 12,500 feddan in the west Qena area.
The study area is located in the southern part of Upper Egypt, bounded by latitudes 25° 45′ 32.28″ and 26° 05′ 36.30″ N and longitudes 31° 57′ 12.30″ and 32° 45′ 6.84″ E and covers a surface area about 2000 km2 (Fig. 1). Climatically, the study area is characterized by desert climatic conditions, dominated by long hot, rainless summer and arid warm winter. The annual mean temperature is 31.5 °C, the annual rainfall is 3.83 mm, the annual mean of relative humidity is 30.68%, and the annual mean value of wind speed is 8.73 km/h (Tutiempo. net, 2018) and the intensity of evaporation is 11.28 mm/day (Mahmoud 2005).
The evaluation of groundwater resources for development requires an understanding of the hydrogeochemical properties of groundwater in the aquifer. The chemical characteristics of groundwater are mainly influenced by rock interaction, sources of recharge, direction and rate of groundwater movement in addition to other factors. Water chemistry plays an important role in hydrologic science, since it can be regarded as a tool revealing various hydrological processes in the past. Moreover, the occurrence of some ions and compounds in groundwater of a specific region may be used as indicators for the origin and formation of groundwater. This work aims to assess the chemical groundwater composition, isotopic signature and determine the origin of groundwater and the main recharge of the Quaternary aquifers in desert environs of the Qena area.
Geomorpholgically, the study area represents a portion along the western bank of the Nile River. The ground surface elevation decreases gradually from the southern limestone plateau to the Nile Valley plain. The giant deviation of the Nile River course, causing the Qena bend, was formed because of the intensive faulting (rift valley) and tectonic activities during different geologic ages. The area is subdivided into four geomorphic units (Said 1962). These are the young alluvial plains (the cultivated lands), the old alluvial plains (the Nile terraces which are a high level of the cultivated lands), the watershed area (the southern calcareous plateau) and water collectors’ areas (alluvial fans and hydrographic basins) (Fig. 2).
Geologically, the sedimentary succession overlying the Precambrian basement rocks in west Qena area is belonging to the Paleozoic, the Upper Cretaceous, the Tertiary and Quaternary (CONOCO and EGPC 1987). A brief description of such succession is given in the following from older to younger (Fig. 3):
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Paleozoic—lower Cretaceous, which area composed of sandstone with intercalations of mudstone related to the Nubian Sandstone Formation.
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Upper Cretaceous, differentiated into Duwi Formation, which compose of phosphatic beds intercalated with shale and marl and Dakhla Formation that formed of shale with marl.
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Paleocene, differentiated into chalk and limestone of lower Tarawan Formation and shale of upper Esna Formation.
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Eocene, include chalk to chalky and dolomitic limestone of Thebes Formation.
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Pliocene, composed of interbedded clay and sand with silt of Madamud Formation.
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Pleistocene, differentiated into three main deposition stages (paleonile/protonile, prenile and neonile), this succession composed of lower thick clay unit with silt and marl of Armant and Issawia Formation, the middle unit formed of massive sand with intercalated clay lenses and conglomerates of Qena Formation and the upper sandy silt unit with pebbles of Dandara Formation.
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Holocene, deposits are represented by Wadi fill deposits consisting of silty clay, sand and gravels.
Tectonically, the study area is slightly affected by tensional forces leading to several normal and wrench faults of NW–SE and NE-SW trends and mainly affecting the Eocene limestone. These faults are associated with some parallel folds (Fig. 4) (Said 1962 and Youssef 1968).