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Groundwater properties and potentialities in the Precambrian rocks, Hafafit area, Southeastern Desert, Egypt

Groundwater is the main water resource for drinking, domestic, irrigation and industrial purposes in the study area as a result of limited natural fresh water. The water scarcity and shortage in Egypt due to population growth, agriculture expansion, industry development, climatic changes and water pollution lead to search about new water resources to overcome the depletion of annual individual share of water such as evaluation of groundwater in Precambrian aquifer, Southeastern Desert, Egypt. Egypt is under water scarcity due to difference between water demand and available water resources, so, we need to search and explore new water resources in Egypt, especially in Southeastern Desert of Egypt. The importance of Southeastern Desert of Egypt represents one of the famous regions for mining such as gold (El-Sukkari gold mine), ilmenite (Abu Ghuson) and other economic ores, therefore the area crowded with touristic villages and resorts parallel to the red sea coast with industrial, commercial and agricultural expansion in the area. The previous factors lead to necessity of qualitative and quantitative evaluation of groundwater resources to reduce the gap between the available water resources and water demand. Applications of remote sensing and Geographic information system techniques have been utilized to investigate the hydro-geological framework and hydrochemistry of fractured Precambrian and coastal aquifers system in Southeastern Desert of Egypt. The aim of the work is evaluation and exploration for new water resources in Southeastern Desert of Egypt dealing with groundwater properties and potentially in the Precambrian aquifer, Hafafit area, Southeastern Desert of Egypt. The groundwater potentialities of Precambrian and coastal aquifers have been studied using remote sensing, geomorphology, hydrology, hydrogeology and geophysics techniques. The groundwater properties of Precambrian and coastal aquifers have been studied using remote sensing, petrography and mineralogy and hydrochemistry techniques. The area is limited by longitudes 330 50/ - 350 45/ 00// E and latitudes 240 00/ - 250 15/ N and covering an area about 17290 Km2. The study area lies within arid desert conditions based on degree of aridity with air temperature and rainfall are variable from summer to winter. The temperature ranges from 22-36 Co with average 28 Co, The average annual rainfall ranges from 3 to 50 mm/year, some intense rainfall events (often 60mm.h-1). The average annual wind velocity is 18.7 km/hour. The intensity of evaporation is 10.1 mm/day. The mean annual relative sunshine ranges between (80-106 %) from season to another, the annual relative humidity varies between (32 % -60%) from winter to summer. In regard to geological setting of the area compose mainly of sedimentary rocks in the coastal line and Precambrian rocks to the west from the coast. The coastal plain sediments include tertiary and quaternary sediments, which classifie into paleogene sediments appear as Abu Ghuson Formation is belong to Oligocene age and Neogene sedimentsare belong to Miocene and Pliocene age include [Ranga Formation, Um Mahara Formation, Abu Dabbab Formation, Sabakha Formation, Um Gheig Formation, Samah Formation, Gabir Formation, Shagra Formation and Samady Formation]. The Precambrian rocks range from the oldest to youngest as [paragneisses and migmatites, geosynclinals metasediments, cataclastic rocks, metavolcanics, serpentinites, metagabbro-diorite complex, older granitoids, Dokhan volcanics, Hammamat group, younger gabbro, younger granitoids, dykes and plugs and alkaline ring complexes]. The petrological studies include the mineralogical compositions of rock-bearing minerals that help to understand chemistry of groundwater and hydro-chemical processes such as water-rock interaction, leaching and dissolution of these minerals in groundwater. The polarized microscope utilized to describe about eighty thin sections demonstrate rock units in Wadi Hafafit and about 100 photomicrographs to explain petrographic features of different rock units. The litho-stratigraphical sequence of Precambrian rocks in wadi Hafafit are classified into two main groups, Infra-structure rocks include [migmatites and gneissic granitoids, psammitic gneisses, biotite and hornblende gneisses, amphibolites, pelitic schist and myllonitic rocks], Supra-structure rocks include [serpentinites, foliated meta-gabbros and metavolcanics], late intrusive includes [late granitoids] and post granite dyke includes [dykes and veins]. The petrographic description of wadi Hafafit rock units are migmatites compose of alternating palesome (biotite and chlorite) and neosome (quartz, plagioclase and k-feldspar), these rocks characterize by banding structure. The gneissic granitoids categories into gneissose tonalite and gneissose granodiorite exhibit gneissose, hypidiomorphic and perthite textures. The pelitic schists differentiate into biotite-garnet schist, muscovite biotite schist, tremolite-actinolite schist and mylonitic pebbly schist, these rocks appear schistosity texture. The psammitic gneiss, biotite gneiss and hornblende gneisses are display gneissosity texture. The amphibolite rocks show schistosity texture, the myllonitic rocks distinguishe into cataclastic granite, mylonite, ultramyllonite and phyllonites. The serpentinites comprise antigorite serpentinites, antigorite carbonate rocks and talc carbonate rocks. The foliated metagabbro characterizes by hypidiomorphic and diabasic textures, metavolcanics appear as meta-andesite rocks display the glamero porphyritic texture. Late granitoid rocks expose in the outer part of the domal structure, intruded migmatites and amphibolites, these rocks include syenogranite and monzogranite with hypidiomorphic and perthite textures. The post granite dykes include aplitic dykes, dolerite dykes, pegmatite veins and quartz veins. The Petrographic characterization explains that the studied area is consisting of two large units corresponding to stratigraphic regional sequences of Infra-structure unit and Supra-structure unit. The rocks of Infrastructure Unit are essentially alumino-silicate rich rocks and compose mainly of quartz, plagioclase, K-feldspar and micas (biotite and muscovite). Consequently the chemistry of groundwater in this part will be the result of aluminum-silicates rocks-water interactions which lead to the release essentially Si, Al, Na, Ca, and K as chemical elements. This is appearing in meta-sediments aquifer and granitic aquifer.In contrast, the rocks of Upper Structure Unit (Supra-structure) are predominately basic and ultrabasic rocks deriving of oceanic crust. These rocks compose mainly of olivine, pyroxenes and magnetite with antigorite, talc and carbonates (calcite and magnesite) as a secondary minerals formed from alteration. The groundwater of this unit is largely enriched with Si, Mg, Ca, HCO3 and Fe. As these types of basic rocks contain a significant part of sulfide minerals their alteration can produce sulfate formation. This is appearing in Meta-volcanic aquifer and basic-ultrabasic aquifer. The remote sensing technique is one of the most important tools to discriminate the rock units, mapping of rocks and extraction of lineaments. The remote sensing is a powerful tool due to efficiency, saving money and time. The satellite image data [landsat-8 OLI] utilize for discrimination rock units using flash atmospheric correction method and histogram equalization is applied to enhance the Landsat image. The true color composite, false composite color [FCC], color ratio composite [CRC], principal component analysis, unsupervised and supervised techniques are used to discriminate the rock units.The remote sensing technique is applied to distinguish between rock units in Wadi Hafafit for the area 312 Km2 [migmatites and granite gneisse, psammitic gneisse, biotite-hornblende gneiss, amphibolite, serpentinites and talc carbonate, metavolcanics and late granitoids]. The false composite color ratio [FCC] includes [(4,3,2), (7,5,3), (6,5,7) and (1,6,5)] in RGB. The color ratio composite [Band ratio] comprises [(6/2, 6/7, 6/5*4/5), (6/7,5/6,4/2), (5/7, 5/1, 5/4*3/4) and (6/4,4/2,7/6)]. The principal component analysis includes [(PC1, PC2, PC5), (PC1, PC4, PC2), (PC2, PC4, PC1) and (PC3, PC4, PC1)]. The lineaments work as flow paths of groundwater and used for groundwater exploration and prospecting.The increase of lineaments numbers, density, width and intersection is help to increase the probability of groundwater occurrence. The decorrelation stretch and saturation stretch, principal component analysis (PCA) techniques are used to enhance the Landsat-8 image for lineaments extraction. The automatic and manual extraction techniques are applied in this study.The feasible zones for groundwater potentiality evaluation are detected in older granitoids, meta-sediments and metavolcanics, these zones are suitable sites for borehole drilling in regard to recharge and geophysical exploration result. In spite of the dykes work as barrier for groundwater movement, these dykes represent highly fractured zones and suitable regions for groundwater potentiality. The geomorphology of the area classifies into [high lands (Watershed areas), Red Sea coastal plain and low lands (water collectors)]. The morphometric analysis and synthetic Snyder’s unit hydrograph methods were applied for thirty-five catchments using Digital Elevation Model (DEM) to explain gemorphological and hydrological behavior of drainage network in the study area, the results will be use for soil and water management. The morphometric parameters classify into five categories utilizing morphometric method [Intermediate parameters (basin area, basin perimeter, basin length, basin width, total basin relief, stream number and stream ordering), Catchment shape parameters (shape factor, form factor, elongation ratio, circulatory ratio and compactness coefficient), Catchment elevation parameters (relief ratio, relative relief ratio, gradient ratio, watershed slope, and Melton ruggedness number), Drainage network length parameters (stream length, stream length ratio, length area relation, drainage density, drainage texture and length of overland flow and texture ratio), Drainage structure parameters (drainage frequency, bifurcation ratio and weighted mean bifurcation ratio). The synthetic Snyder’s unit hydrograph method in ungauged watersheds was applied to compute the peak discharge and time base in these watersheds based on the physical features and constant coefficients. The time to peak is important evidence for detected the sufficient time for the residents and governmental assistance to help residents to leave the high flood risk zones. The geophysical well logging is applied for nine wells using [Short normal resistivity, Long normal resistivity, Self-potential, Single point resistance, Natural gamma and Borehole Temperature] for describe the subsurface lithology. The stratigraphic correlation of boreholes derived from well logging explains three main layers, the first layer [weathered, fragments and Wadi deposits] in Precambrian rocks and coral reefs in coastal area. The second layer ranges between [weathered rocks, clay and limestone]. The third layer [weathered rocks or limestone]. The obtained hydrogeological cross-sections through the area using well logs and previous geophysical data reveal three main layers covering the study area, Wadi deposits layer ranges in thickness between 15-60 m, fractured basement rocks range in thickness between 20-100 m and massive basement rocks depth range between 40-250m. The structural features affect the massive basement and the overlying succession which control the depth of the massive basement rocks. The results are confirmed previous geophysical and hydrogeological studies and classified the water bearing formations based on these results. The hydrogeological framework of the area comprises six aquifer system includes Red Sea Coastal sediments (Miocene and quaternary aquifers), fractured Precambrian aquifers (meta-sediments aquifer, metavolcanic aquifer, granitic aquifer and basic–ultrabasic aquifer). The piezometric map has a contour of water level range between (0.5 – 590 m), the map depict the dome piezometric in Precambrian mountainous part indicating the high recharge from rain fall.The water is outlets into two directions, the first to the east in the direction of Red Sea and the other in the direction of Nile River. The maps showing radial divergent water table, two axial domes in center of the study area divided the water in equally into the east (Red Sea) and west (Nile River). The hydrochemical analysis of major and minor elements were detected by Inductively Coupled Plasma Mass Spectrometry (ICP-MS), University of Pau (France), the alkalinity and chloride were measured by titration method in Hydrasa laboratory of the Institut des Milieux et Matériaux de Poitiers (IC2MP). The physical properties of groundwater indicate by PH, EC, color and salinity. The ion balance error for all the samples are minimum than 5% except sample No. 28 of Hafafit 4 is 7.85 may be due to organic matter, The total cations has a positive correlation with total anions indicating the accuracy of hydro-chemical analysis. The low pH value of eastern part of the study and the high pH value of the western part of the study area. The Ec value ranges between (1.48 - 21.1) ms/cm, these values increase toward the Red Sea coast and decrease in the western part of the area. The total salinity of groundwater samples ranges between (947.2-13504) ppm, indicates that the salinity of the groundwater increase in the direction of Red sea and decrease in the direction of River Nile. This is attributed to the sea water intrusion in the coastal and coral reef aquifers, the lithology of the water bearing formations, ancient sea water intrusion, evaporation, discharge and recharge. The Major ions are (Ca-2, Mg+2, Na+, k+, Cl-, Br-, SO4-2 , PO4-2, CO3-- and HCO3-) composed nearly 98% of total mineralization in groundwater. The TDS and electrical conductivity (EC) are highly correlated with each other and they have a positive correlation with Ca, Mg, Na, K, and Cl. The calcium in coastal aquifer ranges between (27.3-1354.5) ppm and calcium in Precambrian aquifer about (130.2-1550.3) ppm. The magnesium in coastal aquifer varies from (30.16-426) ppm and magnesium in Precambrian aquifer about (28-1062) ppm. The sodium in coastal aquifer ranges between (427.9-2071) ppm and sodium in Precambrian aquifer varies from (171.9-3582) ppm. The potassium in coastal aquifer varies between (7.7-57) ppm and coastal aquifer in Precambrian aquifer ranges between (3-102) ppm. The total carbonates in coastal aquifer about (78.1-413.6) ppm and total carbonates in Precambrian aquifer varies from (45.8-1412.5) ppm. The chloride in coastal aquifer varies from (637.5-5366.6) ppm and chloride in Precambrian aquifer ranges between (270.8-5378.9) ppm. The bromide in coastal aquifer differs from (0.38-21.3) ppm and bromide in Precambrian aquifer ranges between (0.6-30.9) ppm. The sulfate in coastal varies from (296.4-2248.4) ppm and sulfate in Precambrian aquifer ranges between (197.6-4676.5) ppm. The phosphate in coastal aquifer varies from (0-15) ppm and phosphate in Precambrian aquifer ranges between (0-83) ppm. The minor elements present in low concentration in groundwater (less than 0.1 ppm). The minor elements were determined. These are [SiO2, Al, iron (Fe++ and Fe+++), Manganese (Mn++&Mn+++)]. The average silica content in coastal aquifer ranges from (17.9-35032) ppb and the average silica content in Precambrian aquifer varies between ranges between (21.5-32292) ppb. The manganese concentration in coastal aquifer differs from (1.3-2791) ppb and (1.2-606) ppb in Precambrian aquifer. The aluminum concentration differs from (13.6-82) ppb and iron concentration varies from (53.28-258.4) ppb. The groundwater classification based on cations and anions ratio using the nomenclature (Bazilevich and Pankova, 1968). The common cations are Ca-Na in the eastern part of the area due to recharging from Red Sea water and Na in the western part of the area. The common anions are Cl in the eastern part of the area due to Red Sea water intrusion and (SO4-Cl and Cl-SO4) in the western part of the area. A classification of groundwater type can be proposed that three groundwater types are predominated, the Cl-Na type is predominated in ally groundwater aquifers [granitic, metavolcanics, basic-ultrabasic, meta-sediments and Quaternary-Miocene aquifers], Cl-Ca type is predominated in granitic and basic-ultrabasic aquifers and SO4 is occurred in metavolcanics, granitic and metasediments aquifers. On the other hand, the Na type is characterized Granitic, meta-volcanics and meta-sediments aquifer, while, the Na-Ca is dominated in basic-ultrabasic, granitic, metavolcanics and Quaternary-Miocene aquifers. The saturation indices minerals are classified into, Carbonate group (aragonite, calcite, dolomite, strontianite and rhodochrosite), sulfate group (gypsum, anhydrite and celstite), silicate group (quartz, SiO2, chalcedony, chrysotile, sepiolite, sepiolite (d) and talc), oxides group (hausmannite and pyrolusite), hydroxides group (pyrochroite), oxyhydroxydes group (manganite), phosphate group (hydroxy-apatite) and halides (halite). The saturation indices results are under saturation minerals reveal dissolution in water such as [strontianite, gypsum, anhydrite, celestite, SiO2, sepiolite (d), pyrolusite, hausmannite, pyrochroite, manganite, halite], over saturation minerals precipitated in water such as [calcite, aragonite, dolomite, rhodochrosite, quartz, talc, hydroxy-apatite] and Rhodochrosite, chalcedony, chrysotile and sepiolite are saturated in some samples and unsaturated in others. The hydro-chemical processes include [salinization, weathering, evaporation, mixing and ion exchange], which influences the groundwater quality.According to the salinization, the most of Precambrian groundwater samples in the western part of the area are show meteoric fresh water origin and coastal groundwater samples in the eastern part of the area are display the marine water origin. The most of Precambrian and coastal groundwater samples are subjected to silicate weathering. The Gibbs diagram indicates all the groundwater samples are subjected to the evaporation process. The Precambrian and coastal aquifers explain ion exchange process caused by mixing of fresh and saline water except some groundwater samples depict reverse ion exchange. The evaluation of groundwater quality is applied to determine suitable and safety factors in drinking, livestock, domestic, irrigation, building and industry purposes. The groundwater classification based on salinity (Chebotarev, 1955), 6% fresh water, 40% brackish water and 54% saline water. The groundwater samples are unsuitable for drinking and domestic purposes based on (WHO, 2006). The groundwater samples are unsuitable for laundry use based on (Hem, 1989).The groundwater suitability for poultry is suitable in wells number (1,9,13,24 and 27), horseis suitable in wells number (1,2,3,4,7,9,10,11,12,13,19,21,23,24,25,26x,26,27,28,30,31,32 and 34), Cattle (dairy) is suitable in all wells except (5,8,14,15,16,17,18,20,22,29,33 and 35), Cattle (beef) is suitable in all wells except (5,8,14,22 and 33) and Sheep (adults)is suitable in all wells except (14). The groundwater suitability for irrigation purpose based on TDS represents 29% suitable and 71% unsuitable, based on chloride concentration represents 3% suitable and 97% unsuitable, based on Wicox,s classification represents 3% suitable and 97% unsuitable, based on sodium ion percent (Na%) represents 14% good, 40% permissible, 37% doubtful and 9% unsuitable. The groundwater suitability based on SAR represents 37% excellent, 48% good, 6% doubtful, 9% unsuitable. The groundwater suitability for building purposes reflects all samples are not suitable except El-Jimal and El-Sheikha Amira wells can be utilized without harmful effects. The groundwater suitability for industrial purposes shows that the groundwater wells [SK, HF1, HF2, HMD, MUR, JIM, AMR, BRM, HF3, HF4] are suitable for petroleum and mining industries.

Keywords : Egypt, South-Eastern desert, precambrian aquifer, potentialities, hydrochemical processes, remote sensing, hydrology, geophysics.