Although WHO does not suggest any health-based guideline value for pH, concerning aesthetic aspect, a value range of 6.5 - 8.5 is established for pH. The pH values of groundwater samples in the study area showed that this parameter varied between 7.22 and 7.9 in 2013, which means they were all in the permissible range. All samples had values more than 7, indicating slightly alkaline nature of the samples.

pH role as an operational water quality parameter is indisputable fact. Disinfection of water with chloride, which is one of the stages in water treatment procedure, needs the pH value to be less than 8 to be satisfactory, it even may be inconclusive in pH values above 9. Moreover, to protect the water distribution system, including mains and pipes, from corrosion, the pH has to be managed. Otherwise, corrosion may cause contamination and impact on taste, smell and appearance of drinking water. High pH value in water causes faster scale formations in water heating equipment [15] [16] . On the other hand, low pH in groundwater leads to acidic condition which causes dissolution of insoluble carbonates in soil and limestone formation in water. This phenomenon results in the increase of impurities such as sulfates, chlorides and silicates concentration in groundwater [4] .

Dissolution of organic substances including cations such as sodium, magnesium, calcium, iron, and aluminum, and anions like chloride, nitrate, sulfate, and phosphate has an influence on the ability of water to pass the electrical current, which is called Electrical Conductivity (EC). Electrical conductivity of groundwater could be affected by geology of the basin and the bedrock [17] . The dominant water quality guideline for crop yield is the peril of water salinity which is measured by EC. High EC value irrigation water causes physiological drought. It means that plants root are unable to compete with ions for water in soil. By increasing the EC available water to crops decreases. This phenomenon has an adverse effect on crop yield [18] .

In Sharif Abad basin EC values of water samples in 2013 varied from 6040 to 21,050 μS/cm, which according to WHO standard is significantly higher than maximum permissible value of 1400 μS/cm for drinking water [15] . Spatial distribution of EC throughout the study area is shown in Figure 4 indicating higher concentration of total salt in the eastern part, near the Salt Lake. It can be concluded from Figure 4 that the dominant reason for EC increase in this basin is saltwater intrusion from the Salt Lake. Moreover, annual average of EC values from 2004 to 2013 shows a continuous growth (Figure 5).

Presence of chloride is natural in different kinds of water. Cl (Chloride ion) is the major natural form of this element which is highly stable in groundwater [3] [6] [16] . Both natural sources such as precipitation, evaporates, dissolution and weathering the halite and anthropogenic sources like domestic and industrial

effluent, urban runoff, septic, fertilizer, industrial and animal waste and also saline intrusion can be the origin of chloride in groundwater [15] [19] - [24] . High concentrations of chloride may lead to escalate the corrosion of distribution system which increases the metal concentration in drinking water. It also can turn the water taste to salty and causes laxative conditions for people not adapted to it [15] [25] . WHO standard for chloride is based on taste. Concentration exceeding 250 mg/L may be detectable and concentration more than 600 mg/L would have a noticeable impact on the suitability of water for drinking purpose.

In 2013, chloride concentration values in water samples of the study area varied between 1588 and 5707 mg/L, indicating that the water samples are highly salty. Chloride concentration in all samples was dramatically higher than prescribed WHO limit. Chloride distribution in 2013 (Figure 6) implies that Cl concentration is higher in eastern part of the study area that is closer to Salt

Lake. Two dominating phenomena causing high chloride concentration can be saltwater intrusion from east, where Salt Lake is located, and salt dome in northern part of the study area (around W3 and W8). Diagram of average annual chloride concentration values shows a continuous increase from 2004 to 2013 (Figure 7).

TDS consists of mainly inorganic salts including calcium, magnesium, potassium, sodium, bicarbonates, chlorides and sulfates and a slight amount of organic substances which are dissolved in water. The origins of TDS include natural sources and also industrial discharges, urban runoff, sewage, fertilizers, road run off (containing salts used for road deicing) [15] . There is always a relationship between TDS and the electrical conductivity of water [26] [27] . High concentration of TDS can have an unfavorable effect on people and makes the water unpalatable. Too high or too low TDS concentration can lower the effectiveness of wastewater treatment plants and industrial processes that use raw water [28] . The concentration more than 1000 mg/L for TDS in water can cause scale build-up in distribution system, heaters, boilers and household appliances. According to WHO there are no reliable evidence on effects of drinking water with high TDS concentration on human health, so no health-based guideline was suggested. However, based on taste consideration, maximum concentration of 1000 mg/L was proposed for TDS [15] .

In this study area, the TDS values of samples were in the range of 4065 - 14,445 mg/L in 2013. None of water samples were permissible for drinking or even irrigation purposes. The TDS distribution of groundwater in 2013 and also average annual of groundwater TDS concentration in this study area during 2004 to 2013 is shown in Figure 8 and Figure 9 respectively.

Categorization of groundwater based on their hydrochemical properties is requisite to establish the suitability of it. This classification is presented in Table 4 [29] .

Hardness is mostly caused by dissolution of calcium and magnesium and also other metals. Since hard water hinders home laundry and washing by reducing the effect of soap and synthetic detergent and also can result in scale formation in boilers and industrial equipment, it is an important matter for industrial and domestic water users. On the other hand, hardness less than 100 mg/L declines the water buffering capacity and causes corrosion in water pipes [15] [30] .

Drinking very hard water for long might give rise to heart disease and

urolithiasis [31] . However, there is some evidence that very soft water may cause an unfavorable effect on mineral balance of human system [15] .

Concerning the adequacy of water for domestic use the maximum allowable level of 10 meq/L (500 mg calcium carbonate/L) in drinking water, is proposed by WHO. Nevertheless, suitability of TH level in water may differ in different communities, for example in some countries hardness level exceeding 500 mg/L is accepted by consumers in some cases [15] . Following formula is used in this study to calculate TH of the groundwater [32] .

where TH is reported in mg/L as CaCO₃ and Ca and Mg in meq/L.

In this study area, the TH values of water samples were in the range of 1076 - 3430 mg/L in 2013, signifying that all the water samples were in the “very hard” category. Water samples were classified based on general scale for hardness in Table 5 [30] .

Sodium is the sixth ample element on earth and broadly exists in soil, plants, water, and food [33] . Sodium is also one of the main cations that naturally exist in fresh water. However, Na concentration is usually lower than Ca and Mg [16] . Sodium may discharge to groundwater through road deicing chemicals, water treatment chemicals, domestic water softeners and sewage effluents [33] . Since there is no evidence of contribution of sodium presence in drinking water to hypertension occurrence, no health based guideline is recommended by WHO. Nonetheless, based on taste adequacy, maximum limit of 200 mg/L is proposed [15] .

The sodium concentration in water samples of the study area were in the range of 1040 - 3827 mg/L in 2013. All the concentration in water samples exceeded the standard value suggested by WHO. The average concentration of sodium in water samples was relatively higher than Ca and Mg (Table 2). This may be caused by geology of the study area, presence of the salt domes, and/or saltwater intrusion from Salt Lake. The growth of annual average of sodium values of groundwater for this basin during past decade is shown in Figure 10.

Naturally, sulfate exists in drinking water [34] . Highest concentration of sulfates typically happens in groundwater and originates from natural resources. They also may enter the groundwater through industrial waste and atmospheric deposition. Sulfate level more than 250 mg/L results in conspicuous taste and corrosion of distribution system [15] . High level of sulfate may also contribute to diarrhea, especially when the concentration changes abruptly from low to high in drinking water. This may cause gastrointestinal irritation to the human system [32] [34] .

According to WHO sulfate concentration higher than 400 mg/L would considerably impact the potability of water. Sulfate values of samples were in the range of 883 - 3336 mg/L in 2013. Comparing with WHO prescribed standard,

all the samples were significantly out of standard range.