الفهرس 
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Abstract
El Salhia El Gedida area is located to the east of the Nile Delta, between Ismailia and El kassara Canals. It is bounded by latitudes 30o 32` 24˝ and 30o 40` 12˝N and longitudes 31 o 49` 12˝ and 32o 11` 24˝E. It represents one of the major reclamation projects in Egypt which depend mainly on groundwater for irrigation activities.
The aim of the present study is to identify the different sources of groundwater in the Quaternary aquifer. As well as an attempt has been conducted to identify the potential geochemical reactions responsible for the different chemical constituents and solutes in the Quaternary aquifer, the hydraulic connection between the underlying Miocene aquifer and the Quaternary aquifer is confirmed.
In order to achieve these aims and objectives, the followings are conducted; 1. One hundred and three groundwater samples are collected from the study area representing the Quaternary aquifer and directly chemical analysis has been carried out at the hydrogeochemistry department at the desert Research Center. 2. thirty eight samples are collected carefully for isotope analysis at the University of Arizona.
Geomorphologically, the area represents deltaic plain which is classified into old and young deltaic plains. The old deltaic plain is represented by Abu Sweir plain, while the young deltaic plain is represented by El Salhia sand plain. The Quaternary aquifer is composed of aolian and old deltaic deposits which consist of sand and sandstone with intercalations of clay. Groundwater flows from the south and north directions (Ismailia and El Kassara canals and their branches) towards the middle and eastern parts of the study area.
Halite dissolution was found to be responsible for sodium content in groundwater, whereas excess sodium is investigated to be released from silicate weathering reactions or due to return flow after irrigation. Most groundwater samples appeared to lie at / or close to equilibrium with montmorillonite, kaolinite and illite. The results of the geochemical modeling (Netpath-win), the water-rock and mass-transfer reactions for two hydrological flow paths indicated the following; the incongruent dissolution of silicate minerals, the precipitation of clay minerals and calcite in the Quaternary water bearing deposits.
Water samples from the Quaternary aquifer have δ18O between 0.925‰ to 3.4‰, with an average value of 1.99‰; and they have a variable content between 7.13‰ to 24.95‰ for δD with an average of 16.94‰. Water which is enriched in heavy isotopes reflected a recharge from the surface water canals after the construction of the Aswan high Dam (AHD); the surface water is enriched in heavy isotope as well (δ18O= 3.34‰ and δD= 25.33). The depleted values of heavy isotopes reflected an old water that had infiltrated into the aquifer before the AHD. Water of most depleted isotope content may reflect the upward leakage of paleowater from the Miocene aquifer (-6.76‰ and -33‰ for δ18O and δD). Most of the collected groundwater samples suggested meteoric origin that has been subjected to evaporation prior to infiltration into the considered aquifer. The Dual approach of δ 34S and δ 18O (SO4) indicated three different sources of sulfate which are coming from either; terrestrial, atmospheric, and from the Quaternary aquifer. It also indicated that the Quaternary aquifer is connected with the underlying Miocene aquifer through deep faults.
The constructed R-mode factor analysis has been made then rotated on ten variables (EC, pH, Ca, Mg, Na, HCO3, Cl, SO4, SiO2, and NO3) and indicates two principal factors F1, F2. Factor 1 has high positive loadings with EC, Ca, Mg, Na, K, Cl, SO4 and NO3 (>0.5) indicating leaching of secondary salts. Factor 2 has positive loadings with NO3 and SiO2 reflecting signature of natural water recharge and rock-water interaction. The result of the Hierarchical cluster analysis (HCA) is presented as a dendrogram where all groundwater samples are classified into three major groups. group 1 is further divided into three subgroups; also group 2 is subdivided into two further subgroups.
36% of the groundwater samples in the study area are suitable for drinking. On the other hand, 64 % of groundwater samples are unsuitable for drinking because their higher salinity as well as their major ions concentrations are more than the permissible limits.
According to Wilcox`s classification, 4% of groundwater samples lie in the excellent to good class of irrigation, while 4% lie in good to permissible class of irrigation and 23% of the groundwater samples lie in the permissible to doubtful class of irrigation. On the contrary, about 33% lie in doubtful to unsuitable class of irrigation, and the rest of the groundwater (36%) are placed in the unsuitable water class of irrigation. Based on Richard`s classification, most of the groundwater samples (14%) are considered good for irrigation because they lie in the good water class (C2-S1 and C3-S1), while 21% lie in the moderate class for irrigation (C2-S2, C3-S2 and C4-S2). 25% are intermediate. 22% are considered bad water class, while the rest of the samples are out of the scale.
Recommendations
1- Many wells have water that exceeds the Egyptian standards of drinking water quality, and wells owners have to be attentive of the risks of such water.
2- Water treatment should be applied to the unsatisfactory water for drinking or providing source for drinking water.
3- Further monitoring for the changes in water levels and salinity with time in the study area is necessary.
4- Regulating Planting crops according to salinity in the study area is required.
5- Excessive pumping at the middle part of the study area increases groundwater salinity, so that regulating the pumping for groundwater management is required.