الفهرس 
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Abstract
Groundwater in Assiut Governorate has a crucial importance, as it is the second source of fresh water used for domestic, agricultural, and industrial purposes. This study aims to present an integrated study about groundwater pollution in Assiut Governorate by evaluating groundwater quality, determining groundwater type and rock source deduction, and assessing groundwater vulnerability. Geographic Information Systems (GIS) has been used to provide spatial analysis distribution maps of the groundwater quality parameters and to find out the groundwater vulnerable zones to pollution by applying the DRASTIC model within ArcGIS 9.3 environment. Furthermore, Aquachem 2011.1.40 software package has been used to plot the piper diagram to determine groundwater type and deduce the geological source of soluble ions.
The data has been obtained for the period from 2006 to 2015. The number of wells that have been examined from 2006 to 2009 is 335, reaching 796 wells by 2013. Moreover, 55 samples were taken from drinking water stations and irrigation wells in 2015 directly by the researcher to check the groundwater quality and type.
The obtained samples from the 335 wells during 2006 and 2009 have been used to conduct two main things; the first one is building the correlation matrix between the groundwater quality parameters, which are major ions, EC, TDS, SAR, Na%, RSC, TH, KI, PI, MH, CAI, and C.R.; the second one is a preliminary evaluation of suitability of groundwater for drinking and irrigation purposes by comparing those parameters to the standards of both (the world health organization (WHO) as well as the Egyptian standards). The un-weighted Arithmetic Water Quality Index (WQIUA) method has been applied to the updated data within 8 years. Seven hundred ninety-six samples were used to assess groundwater quality. Geographic Information Systems (GIS) was used to create maps representing the spatial distribution of groundwater categories. The results revealed that the WQIUA values for drinking purposes are high and most of them are higher or close to 100, which indicates that the groundwater is polluted and unsafe for drinking. On the other hand, the quality index of groundwater for irrigation purposes mostly ranges between 55.78 and 78.38 (poor and very poor category); this means that the groundwater is moderately polluted and therefore suitable for irrigation.
Along with groundwater quality assessment via WQIUA; groundwater types were assessed using the Piper diagram. The samples of groundwater wells have been plotted on the Piper-trilinear diagram to illustrate the hydrochemical facies in order to understand water type. The results revealed that most of the groundwater samples fall in bicarbonate, chloride and mixed zone on the triangle representing the anions. On the other hand, on the triangle of cations on the right side, the majority of data belongs to sodium and mixed zone. Therefore, the water type of most samples in the diamond shape is Na-Ca-HCO3-SO4 facies and Na-Ca-Cl facies. This result confirms that the calcareous structural plateau surrounding the study area has an effect on the groundwater chemistry by interaction between groundwater and limestone rocks of the plateau. Thus; Na-Ca-HCO3-SO4 is the dominant water type in the Nile aquifer along Assiut Governorate. Furthermore, Gibbs diagram is used to determine the correlation between water composition and aquifer lithological characteristics. Gibbs plot showed that nearly all of the groundwater samples plot in the water–rock interaction field and the minority samples are fallen on evaporation zone. Accordingly, the rock dominance field is the common zone in this area, this means that interaction between rock and water has occurred.
The rock source deduction process is conducted using different essential ratios, representing the criteria of rock-source. The results show that the ratio of Cl to the sum of anions is less than 0.8 for all samples, indicating that the rock weathering is dominant. 71% of all samples confirmed that plagioclase weathering is unlikely; but 29% indicated that the plagioclase weathering is possible for such samples. According to the criterion of TDS values, 78% of all the samples emphasized that the carbonate weathering is dominant; however, 22% underlined that silicate weathering is controlled. Whereas, the ratio of Mg to Ca plus Mg shows that limestone-dolomite weathering is predominant.
Groundwater vulnerability maps were created using generic and pesticide DRASTIC model. The results show that most of the study area are either moderately vulnerable or highly vulnerable to pollution, whereas 55.2 % of the area is moderately vulnerable and 35.4 % has high levels of vulnerability on the map of generic DRASTIC model. However, in the vulnerability map generated by pesticide DRASTIC model, the results indicate that about 64% of the study area has an extreme to high vulnerability to contamination, 34.6% has a moderate vulnerability and small areas occupy about 1.4% have a low vulnerability.