Groundwater quality assessment is considered as a significant topic to make sure possible safe use of this resource. As the population continues to increase, it is necessary to find additional sources of water such as groundwater. Groundwater is deemed one of the major resources for potable water in Assiut governorate especially in rural areas [1] . Methods to incorporate some factors correlated to groundwater quality in a particular index are gradually more desired in local and global scenarios [2] . Using of indicators and indices to monitor the environmental condition can abstract a huge number of characteristics, thus decision makers can be provided by an integrated and more instructive summary [3] . Geographic Information System (GIS) is able to become a strong tool to improve solutions for groundwater resource problems, for assessing groundwater quality, determining groundwater availability, and managing groundwater resources on a national or international range especially when groundwater has a geographical status [4] .

This paper aims to assess groundwater quality using Un-weighted Arithmetic Water Quality Index (WQI_UA), and display spatial distribution of groundwater quality using GIS in Assiut governorate. In view of the previous studies conducted to assess the quality of groundwater it has been shown that the few number of such studies was interested with groundwater pollution and have been applied on limited regions in Assiut governorate. In 1988, Sobih et al. [5] talked about the chemical and bacterial pollution of groundwater by assessing 25 water wells established at Assiut city. Schlumberger geoelectrical depth soundings and horizontal geoelectrical profiling was used to determine the distribution of the contaminated and uncontaminated zones of groundwater in (El-Madabegh) area, northwest of Assiut city [6] . Sebaq et al. (2003) [7] used surface geoelectrical methods for delineation of groundwater pollution in Beni Ghalib area, northwest of Assiut city.

Geographic Information System (GIS) has come into view as “a powerful tool for storing, analyzing, and displaying spatial data and using these data for decision making in several areas including engineering and environmental fields” [8] . GIS has been applied to create groundwater quality classification map depending on the relationship between total dissolved solids (TDS) values and some characteristics of aquifer [9] or based on the correlation between TDS and land use [10] . Some studies developed a GIS-based methodology to design a groundwater monitoring system and to estimate distributed groundwater contamination risk [11] - [13] . GIS technology has been assigned to study groundwater nitrate contamination resulted from agrochemical fertilizers [14] [15] .

Ahmed and Ali (2009) [16] , combined between geochemical modeling techniques and GIS to study an incorporated role of three different processes to evolve groundwater composition, and their effect on quality of groundwater in Sohag governorate, Egypt. In 2009, Dawoud and Ewea [17] developed a numerical model using GIS based widespread database to simulate the stable and temporary flow in saturated and unsaturated zones in Wadi Al Assiuti Area. El-Alfy (2010) [18] applied multivariate statistics and GIS to examine the effects on groundwater resources and the possible contamination sources. Latha and Rao (2010) [19] used Water Quality Index (WQI) and GIS to assess and map groundwater quality. Ratnakanth et al. (2011) [20] , Balakrishnan et al. (2011) [21] and Dar et al. (2012) [22] used GIS techniques to get groundwater quality map.

Study area is considered as a part of the Nile Valley, Egypt. It extends south-north between Sohag and El-Minia Governorates from latitude 27˚37'N to 26˚47'N and extends west-east between New Valley and Red Sea Governorates from longitudes 30˚37' to 31˚34'E, as shown in Figure 1. The total Assiut governorate area is 25,926 km². The extension of the River Nile along study area is about 125 km, and the valley width is between 16 and 60 km [1] . River Nile divides the study area into a western and an eastern part. The Eastern part expands between El-Badary in the South and Manfalut in the North, while the Western part of the study area expands between El-Ghanayim in the South, and Dairut in the North. The sharp declination is the major feature of the fringes of the study area because of the limestone plateau which limits the area from the east and the west, except of the Northwestern part that has a moderate slope [17] . There are some wadies joined with the study area like: Wadi El-Assiuti and Wadi El Ibrahimi in the central east, Wadi Abu Shih in the south east.

Firstly, the quality rating (q_i) was computed by “Equation (1)” for twelve parameters which used to determine validation of groundwater for drinking and purposes as shown in Table 4. It is worth mentioning that q_i isn’t considered representative water quality index of all measured parameters in the year but it is just for individual parameter such as Na, K, and so on. It is clear from Table 4 that all values of Ca and Mg are less than 50 overall the years from 2006 to 2013, this means that the groundwater does not contain dangerous levels of those elements. The quality rating for potassium K was more than 50 in 2006 and 2007 only, but the rest values were less than 50. It is indicated that groundwater does not suffer from increasing of potassium percentage.

The calculated values of q_i for such parameters have been plotted as illustrated in Figure 2 during the period 2006-2013.

The sulfate quality rating (q_SO4) is similar with (q_K), it is also more than 50 in 2006, 2007 and 2008 and then became below 50 during the next period. It is noted that there is an increase above 50 in the quality rating of K,

So₄ and Mn in the years 2006, 2007, and 2008, but the ratios is changed to less than 50 in the period from 2009 until 2013.,

All quality rating indices (q) of Na and Hco₃are limited to between 50 and 100, so sodium and bicarbonates ions have negative effect on groundwater quality. The quality rating index (q) for Cl is high throughout the observed years and it reached over 100, which represented that the water is polluted with high levels of Cl. In other case for Fe, the quality rating (q) rate was low in all observed years except 2006 and 2007. PH rate falls within the permissible limits in almost all wells and its quality rating was less than 100 over all years. According to the point that quality rating of TH reached higher than 100, it indicates that groundwater is classified as hard water. Although the quality rating values of Na, K, Ca, Mg, Hco₃, and So₄ were less than 100 but the quality rating for TDS reached over 100 in all years. This means the groundwater in Nile aquifer system along Assiut governorate is over saturated with total dissolved salts (TDS).

Therefore, quality rating (q) cannot be relied upon alone; all affected variables must be included to get one representative value of groundwater in each year which called the Un-weighted Arithmetic Water Quality Index (WQI_AU) or (Q) as demonstrated in Equation (2).

With regard to quality rating index (q) of the five used parameters to assess the suitability of groundwater for irrigation, Table 5 summarizes the calculation of q_i, whereas, Figure 3 illustrates quality rating index (q_i) of those parameters which are TDS, SAR, Na%, PI, and MR.

It is obvious from Table 5 and Figure 3 that all q_i values of TDS and SAR are below 50, this points to the groundwater has small percentage of these two parameters. While all q_i values of Na% and PI vary between 50 and 100, it means that those parameters have negative effect on groundwater quality. While most values of quality rating index (q_i) of MR exceed 100, it denotes that groundwater is oversaturated with magnesium ratio (MR).

It is noted that it cannot be judged on the groundwater quality using a single factor alone, thus, it must be combined between five parameters to get one representative value which called Un-weighted Arthmetic Water Quality Index (WQI_AU) or (Q).

Data of 796 wells over the eight years have been used to estimate the Un-weighted Arithmetic Water Quality Index (WQI_UA) or (Q) yearly during the period from 2006 to 2013. Table 6 shows the summary of data wells distributed over 8 years

The Un-weighted Arithmetic Water Quality Index (WQI_UA) or (Q) has been calculated yearly by Equation (2) as shown in Table 7. The Un-weighted Arithmetic Water Quality Index (WQI_UA) or (Q) results of groundwater whether it used for drinking or irrigation were plotted in two curves as cleared in Figure 4.

The tabulated results in Table 7 show that WQI_UA values of groundwater for drinking purposes are close to 100 or more than 100. In addition to, the curve of drinking water in Figure 4 is located in two zones which are very poor category and unsuitable category. Hence, the groundwater is polluted and unsafe for drinking. On the other hand, the Un-weighted Arithmetic Water Quality Index (WQI_UA) or (Q) of groundwater for irrigation ranges between 55.78 and 78.38 (poor and very poor category); this means that groundwater is moderately polluted and hardly valid for irrigation.

Secondly, GIS has been used to plot the Un-weighted Arithmetic Water Quality Index (WQI_UA) results to create the spatial distribution map of WQI_UA for drinking water and irrigation water as shown in Figure 5 and Figure 6 respectively.

The results revealed that the suitability of groundwater for drinking varies from location to another. Generally, the groundwater quality index for drinking around river Nile is less than the new reclaimed lands at the fringes of study area. The groundwater in most of the study area belongs to unsuitable and very poor categories, however good and poor categories occupy small areas. Accordingly, the majority of groundwater wells in study area

are unsuitable for drinking.

Figure 6 shows the Un-weighted Arithmetic Water Quality Index (WQI_UA) results of groundwater for irrigation purposes. It is noted that the yellow color covers the most of study area which expresses the poor category. For the very poor category, it occupies small areas on the fringes of Assiut governorate, Wadi El-Asyuti and Abnub from the east side, Bani Adi and Al-Ghanaium on the west side district. The isolated areas in Wadi El-Asyuti and Abnub on the eastern side which have red color are unsuitable category. Consequently, the largest part of the study area varies between poor category and very poor category; this means that groundwater is moderately polluted and hardly suitable for irrigation.

The objective of calculating WQI_UA is to find out quality assessment of water by synthesizing different available groundwater data. Samples of 796 groundwater wells have been used to determine the Un-weighted Arithmetic Water Quality Index (WQI_UA) during the period from 2006 to 2013. The quality indices are worked out for PH, Na, K, Ca, Mg, HCO₃, SO₄, Cl, TDS, TH, Fe and Mn to evaluate the suitability of groundwater for drinking. While, SAR, Na%, PI, MR, and TDS were used to calculate WQI_UA for assessing the suitability of groundwater for irrigation. It is concluded that the groundwater of this study area is not suitable for drinking water but can be

hardly used for irrigation purposes. The results are also supported by the spatial distribution of the WQI_UA map which was generated by ArcGIS 9.3. In case of using groundwater for drinking, the most study area belongs to unsuitable and very poor categories, whereas if groundwater is used for irrigation, the most study area belongs to poor and very poor categories.

Mohamed R. ElTahlawi,Mohamed Abo-ElKassem,Gamal. Y.Baghdadi,Hussein A.Saleem, (2016) Estimating and Plotting of Groundwater Quality Using WQI _UA and GIS in Assiut Governorate, Egypt. World Journal of Engineering and Technology,04,59-70. doi: 10.4236/wjet.2016.41007