Groundwater Quality Assessment for Drinking and Agricultural Purposes in Tabriz Aquifer , Iran

The key goal of the current study was to determine suitable areas of water pumping for drinking and agricultural harvest in Tabriz aquifer, located in East Azerbaijan province, northwest Iran. In the study area, groundwater is the key foundation of water for drinking and farming requirements. Groundwater compatibility study was conducted by analyzing Electrical conductivity (EC), Total dissolved solids (TDS), Chloride (Cl), Calcium (Ca), Magnesium (Mg), Sodium (Na), Potassium (K), Sulfate (SO4), Total hardness (TH), Bicarbonate (HCO3), pH, carbonate (CO3) and Sodium Adsorption Ratio (SAR) obtained from 39 wells in the period of 2003 to 2014. For this purpose, the Water Quality Index (WQI) and irrigation water quality (IWQ) index is respectively utilized. The WQI index zoning exposed that the groundwater of the study area for drinking purposes is categorized as excellent, good and poor water. Most drinking water harvested for urban and rural areas are in the class of 'excellent water’. IWQ index average for the study area was in the range of 25.9 to 34.55. The results revealed that about 37 percent (296 km2) of groundwater has high compatibility, and 63 percent of the study area (495 km2) has average compatibility for agricultural purposes. The trend of IWQ and WQI indexes demonstrates that the groundwater is getting worse over time.


Introduction
About two-third of the earth planet is enclosed by the life-giving liquid which is named water, though 1 percent of the whole amount consists of drinking water which is appropriate for human consumption.
It is obvious that the supreme use of water is for human consumption for responding to his needs.If people use water resources with caution, adequate water with decent quality is sufficient for the existing population (Hashmi et al., 2009).Farming is a prevailing segment of the worldwide economy (FAO, 1994).Farming is notable as the biggest client of crisp water and a noteworthy reason for the debasement of surface and groundwater assets and quality (FAO, 1994).
Groundwater assets are vital for financial improvement, particularly in parched and semi-bone-dry areas (Tlili-Zrelli et al., 2013).The quality of water is identified as the normal, physical and compound condition of the water, and additionally, any adjustment that may have been initiated by anthropogenic action (Venkateswaran et al., 2011;Jafar Ahamed et al., 2013;Khan et al., 2012;Salahat et al., 2014).
The groundwater quality is the consequence of every one of those procedures and responses that follow up on water from the minute it is gathered in the climate until the time it is stored by a well, which is regularly controlled by different physicochemical attributes (Arumugam and Elangovan, 2009).
The combined effects of populace development and extreme harvestation of groundwater have initiated broad exhaustion and corruption of groundwater assets (Amiri et al., 2014).Moreover, it is clear that the quality of agricultural water has an influence on the quality of the soil and accordingly on the harvests which are developed on the soil.The interest in a farming area and the produces items has advanced quickly in the most recent century due to populace development.What's more, specialists mention that some elements, for example, more urban areas, more industrialized spaces, inadequate management of the lands and ecological contamination has forced extra weight on prodection of agricultural items (Tanji, 1990;Kwiatkowski et al., 1995).Therefore, viable exploitation of both the farming area and the irrigation water has turned into a crucial part, if not the essential goal, of several agrarian improvement and administration designs.Hence, evaluating the quality of groundwater is imperative.Conventional assessment of groundwater quality is straightforward yet point by point in view of the individual parameters (Mohebbi et al., 2013).Therefore, it is not adequate to give a precise representation of water quality.Hence, water quality indexes have been produced for condensing water quality information in an effectively expressible and justifiable configuration (Saeedi et al., 2010;Ramakrishnaiah et al. 2009).
Typically, the nature of a water system sources is related with its (a) saltiness amount, (b) penetration or porousness danger, (c) particular poisonous ions quality, (d) trace elements harmfulness; and, (e) different various influences to defenseless products.It should be noted that these dangers or negative effects could happen simultaneously, which makes assessing harder to accomplish (Simsek and Gunduz, 2007).Simsek and Gunduz (2007) suggested an irrigation water quality (IWQ) list to characterize water system quality which was based on the five risk groups that were specified above on touchy harvests.
The IWQ index is a strategy in which the linear blending of factors in a collection of water system quality that impact soil quality and harvest yield in a negative way (Adhikari et al., 2011).Numerous analysts have used this index for irrigation water system goal in light of diverse hydrochemical parameters due to its easiness of use and tought particularly for the nontechnical chief (Debels et al., 2005;Narany et al., 2014;Negm and Armanuos, 2016;Narany et al., 2016).
The key water quality index (WQI) was created by choosing and presenting an accumulation function (Simos et al., 2008).WQI index is utilized for qualitative zoning of the aquifers from the drinking aspect and also for determining the proper places of drinking water wells in a lots of research plots such as Effendi and Wardiatno 2015;Chen et al., 2015;Bodrud-Doza et al., 2016;Fijani et al., 2017;Schneider et al., 2016;Khan and Qureshi, 2018;Oyinkuro and Rowland, 2018.A Geographical Information System (GIS) is a capable instrument for putting away, controlling, examining, and mapping spatial information for making decisions in a multiple regions at one time, which fundamental issues is a good example of it (Nampak et al., 2014).Many studies, such as Narany et al. (2014) and Manap et al. (2014) have effectively used GIS in demonstrating the distribution of water quality parameters.It is vital to preserve the sustainability of the aquifer's quality because groundwater in the study area is mostly implemented for agriculture and rural and urban drinking purposes.
Therefore, for achieving a better understanding of procedures and the current form of groundwater quality in the study area, the following objectives were defined: 1) Identifying areas of aquifer feeding 2) Determining the WQI in an aquifer in the 24 time periods 3) Investigating the alterations in WQI for drinking water through the statistical period 4) Checking water quality status in tapping drinking wells and determining suitable locations for extracting drinking water 5) determining the IWQ in an aquifer in the 24 time periods 6) Investigating the variations in WQI for agricultural water during the statistical period 7) Checking water quality status in the agricultural wells and determining appropriate and inappropriate locations for extracting agricultural water

Study Area
The study area is Tabriz plain aquifer situated in East Azerbaijan province, Iran, with an area of 791 km2 (Figure 1).The most surface of the area is cultivated as apples, pears, apricots, peaches, cherries, green beans, leek, spinach and squash.About 40 percent (50 million cubic meters) of Tabriz city (with a population of 1.7 million) drinking water is also provided from the same aquifer.The mean yearly precipitation of Tabriz is nearly 290 mm, which is very low contrasted with the world normal which is 800 mm.The average temperature is 12.5 °C, and as indicated by the De Martonne aridity index, the district of study is categorized as a semiarid territory (Zarghami and Akbariyeh, 2012;Vaezihir and Tabarmayeh, 2015).Water assets of the aquifers start from rainfall, energizes from the streams, groundwater spill out of encompassing mountains, water system return streams water, city and industry wasted waters.Generally, there are three harvesting types in the study area, including harvest for supplying urban water, rural water and agriculture water.The number of urban, rural and agricultural water harvesting wells in the study area are 81, 50 and is 3884 respectively.To provide the best quality drinking water, the position of Tabriz drinking water wells are embedded at the entry of the groundwater flows of the aquifer.Water depth in the area fluctuates between 1.5 and 186 meters and the overall average is 21 meters.Most of the groundwater flow entering to the aquifer is from the southern and southeastern highlands (Asghari Moghaddam and Allaf Najib, 2006;Barzegar et al., 2017).
The highest water level is 2049.56m and the lowest is 1262.8 m.  1).A total of 936 samples were utilized for analysis brief statistical parameters of each well in the studied period is presented in Table 1.The form and the amount of the dissolved elements in the irrigation water identify the quality of it.
Generally, salinity, specific ion toxicity, trace element toxicity and miscellaneous effect to sensitive crops are utilized for evaluating the quality of irrigation water (Wilcox, 1955).

Salinity hazard
In general, under the condition of high electrical conductivity, the crop faces the physiological drought.
Usually, waters with EC values lower than 700µS/cm are categorized as suitable irrigation waters.The arrangement of EC value for organizing irrigation water qualities are presented in Table 2 (Simsek and Gunduz 2007).

Permeability and infiltration hazard
Salinity and sodium adsorption ratio (SAR) are the two common factors which affect infiltration.The SAR value of irrigation water is computed as: Where, [Na + ], [Ca ++ ] and [Mg ++ ] stand for the concentration of sodium, calcium and magnesium particles in water, respectively (Ayers and Westcot, 1985).A grouping of EC-SAR paradigm is exploited to survey the possible risk of penetration in the soil (Simsek and Gunduz, 2007).It has been reported that a high sodium surface is created when the dirt is flooded by waters of high sodium concentration which debilitates the structure of the soil.The soil compresses and after that, it is scattered to minor elements and stops up its pores.Another essential parameter is the content of clay in the soil.When the SAR value gets high and it negatively affects the soil structure because it causes the soil mud particles to scatter (Simsek and Gunduz, 2007).The categorization of water system quality based in its penetration danger is presented in Table 2.

Toxicity of particular particles
A number of ions including sodium, chloride and boron are toxic for plants when their concentration gets high in water or in soil.In the moment when the concentrations of the ions in plants are so to cause harm or decrease in the production, they are thought to be toxic.The degree of toxicity is definite to each plant and also it is depended on the uptake amount.The lasting, enduring sort crops are in great danger to this kind of toxicity when contrasted with the yearly harvests (Ayers and Westcot, 1985).
Chloride ion can be originated in water system and if it collects in the plants it can diminish yields (FAO, 1994).Chloride at low concentrations is an imperative part of ions to crops, however if the concentration values get higher than 140 mg/l the toxicity starts to develop (Table 2).Signs of damage will be existing as burning of leafs or the drying of leaf tissue.The recognition of toxic sodium concentrations is discreetly troublesome contrasted with the poisonous quality of the other particles.Regular toxicity manifestations on the plants include burning of leafs, dead tissues along the outside edges of leafs as opposed to side effects of chloride toxic concentration which ordinarily starts from the extraordinary leaf tip (Ayers and Westcot, 1985).

Toxicity of trace elements
It is a fact that basically lants and creatures need trace elements in low concentration as an imperative portion, but higher amounts of these elements are being poisonous for plants and even people.Arsenic, selenium and chromium could become an abundant danger to groundwater supplies (Narany, 2016).

Other effects
A number of practices such as anthropogenic exercises, farming procedures and utilization of nitrogen fertilizers cause an increase in nitrate of ground waters (FAO, 1994).The alkalinity of water is associated to pH levels.

Irrigation groundwater quality index (IWQ index)
The hydrochemical parameters employed for evaluating the irrigation water quality are selected according to Ayers and Westcot (1985) and Simsek and Gunduz (2007).The minimum and maximum weights of 1 and 5 have been allocated to pH and EC according to their importance on irrigation water quality.Moreover, different weights among 1 and 5 were considered to other hazards due to the significance of their role in irrigation water quality.Furthermore, the scale of rating is altered from 1 as low suitability for irrigation, to 3 as high suitability for irrigation, for every single parameter (Simsek and Gunduz, 2007;Narany, 2016).The suggested IWQ index, which assesses the joint effect of quality parameters is calculated according to Eqs. 2 and 3.
where W is the involvement of each one of the five mentioned hazards, w is the weight of each hazard, N is the total number parameters and R is the rating value as given in Table 3.
According to the unavailability of all water quality data, four risk groups of Salinity, Infiltration and permeability, particularly ion toxicity and miscellaneous impacts to sensitive cops were implemented to determine the quality of the aquifer used for agricultural dedications in the study zone.
After the estimation of the index value, an appropriate examination is done in light of the three unique classes.The IWQ lower than 19 is specified as low, between 19 and 32 as Medium and higher than 32 as high.The qualities is gotten using several rating factors (i.e., 1, 2 and 3) to every parameter without changing its measuring coefficiency, along these lines yielding three diverse values for index (i.e.,39, 26 and 13).The average of these values is utilized to set the upper and lower limits which is utilized as a part of every specific classification (Simsek and Gunduz, 2007) Water Quality Index Horton (1965) was the first in representing the quality of groundwater by indices.WQI is among the numerous tools for representing the data on the nature of water (Naik and Purohit, 2001).WQI is characterized as a rating which indicates the impact of several parameters on the general nature of water (Sahu and Sikdar, 2008).In that capacity, it is a significant marker for the evaluation and administration of groundwater.WQI is assessed in light of the appropriateness of groundwater for human utilization.
Three stages are done for calculating WQI.In the initial step, weight (wi) of each water quality parameter is measured as indicated by its significance in the general nature of water for drinking purposes.At that point, the relative weight (Wi) is figured by Eq (4) by the following formula (Singh, 1992): In the formula above, n is the quantity of parameters.In the second step, a rating of quality (qi) is ascertained for every parameter, and the ratio of its individual standard value is measured based on the rules from the WHO (2011): In the formula above, Ci is the concentration of chemical parameters for water samples which is expressed in mg/L, and Si is the WHO's standard of drinking water for every substance parameter in mg/L.In the third step, the WQI is measured as (Tiwari and Mishra, 1985): Values of WQI are usually processed and then grouped into five excellent, good, poor, very poor and inappropriate classes of water for drinking (Table 4) (Ramakrishnaiah et al., 2009).
12 parameters were included in calculating WQI by the weighted arithmetic technique.Standard of WHO for drinking water for every chemical parameter by the rules of WHO ( 2011) are recorded in Table 5.Every parameter has a weight as for its significance for the nature of water for drinking purposes, and 5 is the maximum weight which stands for the total dissolved solids (TDS) and EC; weight of 4 is allocated to SO4 and TH; weight of 3 is alloted to pH, Cl and Na; and weight of 2 is appointed to K, Mg, Ca, CO3 and HCO3.

Results and Discussion
WQI index computed for 24 periods of May and September between, 2003 and 2014, respectively.The minimum value for WQI index in these 24 periods of time was equal to 12.14 and the maximum value was equal to 300.53.Regression equation between WQI index and time (t) was obtained in order to assess WQI index general procedures in each of the wells studied.(Table 6).6 WQI index value has decreased in 19 wells, while in other wells an increasing trend can be concluded.The decreased WQI index procedure shows an enhancement in drinking groundwater, while an increasing trend shows reduction of drinking groundwater quality.Of the 936 samples obtained from 39 wells in the period between 2003 to 2014, 497 water samples were categorized as 'excellent water', 217 water samples were classified as 'good water', 188 water samples were classified as 'poor water', 31 water samples were classified as 'very poor water' and 3 water samples were classified as 'unsuitable water for drinking'.The average value of the WQI index was determined after calculating the area of Thiessen polygons for each of the 39 studied wells according to the area affected by each of the wells of.Figure 2a displays the average WQI index in the study area during the statistical period.According to this figure, WQI index of the area has an increasing trend.In fact, the quality of groundwater for drinking has been decreased over the time.Despite the decline in the quality of drinking groundwater, the average WQI index of aquifer still is in 'good water' class over the study time.Therefore, a serious and distributive risk of inappropriate water quality cannot be confirmed for the aquifer which is supplying urban and rural water.3a).27 out of 50 wells supplying rural drinking water are classified as 'excellent water', 19 are marked as 'good water' and 4 wells are in class of 'poor water'.According to the results, the condition of urban drinking water wells is very good.But the situation of 4 rural drinking water wells is not appropriate and the position of the wells or the water source of the villages covered by these 4 wells should be changed.Therefore, generally the position of the urban and rural water wells has been chosen carefully.It is recommended that drinking water is supplied from This study disclosed that the use of indicators for evaluating the quality of groundwater can provide a good general overview to water and environmental managers in order to make better management decisions on Tabriz aquifer.WQI and IWQ indexes offer suitable areas for harvesting drinking and agricultural water, respectively.The suitability of water taken from wells in the study area by the type of application is also determined using these indexes.Therefore, water and environmental managers can use drinking and agricultural water suitability maps to change the inappropriate wells location.Agriculture managing organizations can also determine the type, amount, and irrigation of each region's products based on the suitability of groundwater in that area in order to increase the production and maintain the stability of soil type.The results showed that in terms of consistency, the most urban and rural water wells were classified as 'excellent water' and 'good water'.Due to the agricultural water compatibility zoning map in the study area, there is no low suitability range, and the area has high and medium suitability groundwater for agricultural purposes.The WQI and IWQ index changes over the time in the study area show the decrease in groundwater quality for drinking and agriculture purposes, respectively.Water contamination can be controlled by limiting natural, farming run-off and urban land utilize contamination.

Figure 1 .
Figure 1.The geographical position of the study area with sites of sampled wells

Figure 2 .
Figure 2. Moderate gradual changes in the WQI and IWQ indexes in the entire study area Seventy out of 81 wells supplying urban drinking water are classified as 'excellent water' and the rest of the wells are classified as 'good water' (Figure 3a).27 out of 50 wells supplying rural drinking water are classified as 'excellent water', 19 are marked as 'good water' and 4 wells are in class of 'poor water'.According to the results, the condition of urban drinking water wells is very good.But the situation of 4 rural drinking water wells is not appropriate and the position of the wells or the water source of the villages covered by these 4 wells should be changed.Therefore, generally the position of the urban and rural water wells has been chosen carefully.It is recommended that drinking water is supplied from

Figure 3 .
Figure 3. Geographical distribution of studied parameters in the study area

Table 1 .
The statistical properties of the qualitative parameters in Tabriz plain aquifer, during the period between 2003 to 2014

Table 6 .
The linear regression equation between WQI index and time from 2003 to 2014