Ground Water Quality Assessment Using the Water Quality Index, Iraq

Water Quality Index (WQI) has been applying in the present study to assess suitability of groundwater quality for drinking purposes in Amara city, southern Iraq. This was carried out by subjecting twelve groundwater samples, collected from different sites to comprehensive physic-chemical analysis. Ten parameters have been considered for calculating the WQI such as; pH, electrical conductivity, total dissolved solids, sodium, potassium, calcium, magnesium, chloride, sulphate and nitrate. The WQI values shows that 16.66% of water samples falls in good water categories and the others (83.66%) ranged from poor water to unsuitable for drinking purposes under normal conditions and further action for salinity control is required. The high value of WQI at this study has been found to be mainly due to the higher values of EC, TDS, SO 4-2 , Ca +2 , Mg +2 and Cl - where it was found that there is a very high correlation coefficient between them.


INTRODUCTION
Water is one of the natural resources necessary for human survival and economic development (Boyd et al., 2019).However, in arid and semi-arid regions, uneven distribution of groundwater and surface water resources has become a contradiction that restricts living standards and economic development (Brhane et al., 2018).Understanding the relationship between groundwater and water demand for agricultural production is important for sustainable agricultural development (Zanotti et al., 2019).Groundwater has become the main source of fresh water for household, agricultural, and industrial uses due to its simple extraction and low cost (Hasan et al., 2017).In agricultural production areas, irrigation water, surface water and groundwater are closely linked, which has changed the hydrodynamic conditions and led to changes in groundwater hydrochemical conditions (Li et al., 2019).
Therefore, understanding the chemical characteristics of groundwater and its influencing factors are critical to the protection and management of groundwater resources and the sustainable use of groundwater (Madlala et al., 2019).
Ground water is a globally important and valuable renewable resource for human life and economic development.It occurs almost everywhere beneath the earth"s surface as a multiple-layer aquifer (Shahab et al.,2016).Drinking, irrigation, and industrial purposes depend on groundwater resources.Its importance stems from its ability to act as a large reservoir of water that provides "buffer storage" during periods of

61
drought.In rural context, groundwater provides the mainstay for agricultural irrigation and will be the key to providing additional resources for food security.
In urban centers groundwater supplies are important as a source of relatively low cost and generally high quality municipal and private domestic water supply.Due to rapid population growth, urbanization, industrialization, and agriculture, the groundwater is qualitatively and quantitatively under pressure (Nanaini and Suriya, 2020).As per IPCC synthesis report, higher temperature, pollutant loads due to heavy rainfall, and increased pollutant concentrations during drought will degrade the quality of fresh water and endanger drinking water (Jarraud and Steiner, 2012).Surface-groundwater interaction may alter bio-geochemical cycles in soils overlying aquifers (Riedel, 2019).For irrigation and drinking purposes groundwater quality should be monitored continuously to reduce the geochemical contamination risk through appropriate treatment methods (Acharya, 2018).
As of 12 July, 2021 Iraq"s population stands at about 42,143,409 (Worldometer, 2022).Iraq is located in the southwest of Asia and to the northeast of the Arab world.It lies between the latitudes 29 and 37 and the longitudes 38° and 48° with a total area of 438317km 2 of which the water body area of the country is 950 km 2 (Elaiwi et al., 2020).The middle and southern part of the country has a continental climate, varying from subtropical, arid and semi-arid, and shifts to the Mediterranean climate in the north and north-eastern mountain regions with an average annual rainfall of about 216mm (Chabuk et al.,2020).Groundwater resources are considered the key to all human activities and their survival race, particularly in arid regions; development projects depend essentially on the ability to manage these resources and to protect their quality and quantity and utilize them such efficiently.Nowadays, Iraq has limited share of Tigris and Euphrates water that are the main sources of surface water, and main recharge source for surrounding aquifers, especially after the construction of the Ilisu Dam in Turkey on the Tigris river (Yousuf et al., 2018).The rapid continuous increase in population in Iraq and the continuous development in irrigation projects become imperative to maintain and protect the available groundwater resources and to sustainably develop its use.

MATERIALS AND METHODOLOGY Sampling and sample analysis
In this study, groundwater samples were collected from 12 drilled wells with depth of 36 to 100 m from different locations of Ali Al-Garbi in Misan governorate, southern Iraq during January and February 2023(Fig.1).At each of the sites, a GPS was used to get readings of the coordinates of the locations.These wells are mainly used for water supply and irrigation in rural areas., Cl -, K + , Na + , Mg 2+ and Ca 2+ , Details of sampling locations along with their latitude and longitude are presented in Table 1.The ground water samples were collected in acid washed plastic container to avoid unpredictable changes in characteristics as per standard procedures (APHA, 2017).The spatial distribution of sampling points is consistent with the distribution of water wells in each village, which can objectively reflect the characteristics of groundwater extraction in the study area.

Calculation of WQI Index
Water Quality Index (WQI) is defined as a technique of rating that provides the composite influence of individual water quality parameter on the overall quality of water.It is calculated from the point of view of human consumption.Water quality and its suitability for drinking purpose can be examined by determining its quality index.The standards for drinking purposes as recommended by WHO (2017) have been considered for the calculation of WQI.In this method, the weight age for various water quality parameters is assumed to be inversely proportional to the recommended standards for the corresponding parameters (Mishra, 2001;Naik and Purohit 2001).

−
) is assigned a weight (wi) depending on its comparative significance in general water quality and their perceived effects on primary health.
The allotted weight ranges between 1 to 5. The highest weight of five has been given to parameters TDS, EC, Cl − and SO 4 2− because to their major importance in water quality assessment (Boateng, et al., 2016).The least weight of 1 assigned for K + because it does not play relevant part in the assessment of water quality.The remaining parameters were assigned a value between 1 to 5 depending on their importance in the whole quality of water for drinking purposes (Boateng, et al., 2016 ;Bouderbala, et al., 2016).Secondly, the computation of the relative weight (Wi) is given in equation below (1): where the relative weight is represented by Wi, wi indicates the individual parameter weight, n represents number of groundwater parameters.Thirdly, the computation of quality ranking qi for each physiochemical parameter is done through division of its concentration in every water sample with respect to its respective standards suggested by WHO (2017).The result obtained is multiplied by 100 using equation (2): where Q i represents the quality rating, C i indicates the concentration of each ground water parameter in every sample (mgl -1 ), and S i is groundwater quality standard for each physicochemical parameter based on the national quality standard (WHO, 2017) for groundwater.The WQI model can be defined as below (3):

64
In this study, the WQI values were divided into five levels "excellent water" to "water unsuitable for drinking".Table 3 shows water quality classification based on WQI value.

Results and Discussion
The groundwater chemistry is mainly affected by both natural and human factors.Natural factors include regional geological conditions, chemical composition of precipitation, hydrogeological conditions, and water-rock interactions (oxidation, reduction).Human factors include pesticide use, fertilizer use, groundwater extraction, groundwater recharge, and biological and microbial effects.
pH The pH value measures the hydrogen ion concentration in the groundwater.Majority of the representative groundwater sample (Table 2) has pH value of 6.20 to 7.22, at an average rate 7.02.The highest pH value of 7.22 is found at sampling (GW1 & GW8).All samples are within the permissible range (WHO, 2017), except sampling GW10 (pH=6.20),this may be due to the nature of the chemical composition of the soil.Although pH has a less direct impact on water users, it is one of the most critical operational water quality indicators.Higher weights are assigned to pH to determine drinking water quality index (DWQI) which is subjected to change chemically and also, the range of pH is an indicator for heavy metal pollution.

Electrical Conductivity
Electrical conductivity represents all dissolved salts depending on the quantity and quality of dissolved ions and the water temperature (Eaton and Rice, 2017).The results showed (Table 2) an increase in the electrical conductivity values to reach 8250 µS/cm (GW9) and the lowest 731 µS/cm (GW12), at an average rate 3395.58µS/cm, the high percentage of salts in the groundwater is due to the geological nature of the region or may be due to its filtering from the neighboring lands as well as the washing and dissolution process of the constituent salts of the soil surrounding the groundwater (Mansori et al., 2017).
Total Dissolved Solid TDS in the investigation area has a maximum value of 5600 mgl -1 and a minimum value of 568 mgl -1 , with an average value of about 2212.33 mgl -1 .All groundwater sampling were exceeded the maximum acceptable limits points are appropriate for drinking or irrigation purposes according to WHO guidelines.

Nitrate
Nitrogen compounds are the most widespread pollutants in subterranean environments, derived mainly from agricultural non-point sources.Therefore, an increase in nitrogen pollution causes a severe threat to public drinking water supplies and human health.The NO 3 concentration varies from 0.7 to 28.59 mg/l, with an average value of about 7.62 mg/l (Table 2).All other representative samples do not exceed the permissible limit of 45 mgl -1 .Sulfate 66 Sulfate contamination in groundwater can cause human health issues and material damage implications, making the hydrochemical parameter relatively important and are assigned with higher weights.Spatial distribution of sulfate has the minimum and maximum value for groundwater samples and is between 221 and 849 mgl -1 .All samples have exceeded the maximum acceptable limits except sampling GW11 according to international standards.Chloride Concentration of chloride was ranged between 20 and 1600 mgl -1 , with an average value of about 441.5 mgl -1 .In the investigation area, all samples have exceeded the maximum acceptable limit (200 mgl -1 ) according to (WHO, 2017), except samples GW10,GW11 and GW12 they were within the permissible limits.This may be due to the lack of underground drainage systems and poor maintenance.

Sodium and Potassium
Sodium concentration varies from 11.5 to 447 mgl -1 , and 25% of the representative sampling points are within the permissible limits.Na is the dominant ion among the cations and occurs in most of the natural waters.Na contributes about 53 to 69% of the total cations, this is primarily due to silicate weathering and dissolution of soil salts stored by the influence of evaporation, human activities, agricultural activities, and poor drainage conditions.K is a naturally occurring element, but its concentration remains lower than Ca, Mg, and Na.The maximum value is found to be 20 & 33 mgl -1 (GW6 & GW9) and 83.33% of the sampling points are within the permissible limit, indicating potassium complexes under the conditions investigated.

Calcium and Magnesium
Ca and Mg are directly related to water hardness and abundant elements in surface and ground water.Ca concentration is between 96 and 640 mgl -1 , with an average value of about 258.33 mgl -1 , and Mg concentration varies from 5 to 450 mgl -1 , and an average 104.58 mgl -1 .The calcium concentration is permissible in 58.33% of the samples, but 75% of the samples surpass the permissible magnesium limit (WHO, 2017).
Water Quality Index (WQI) Water quality index is calculated to determine the suitability of water for drinking purpose.Water quality index calculated values for each sample are shown the water quality parameters that were considered in the study using WHO standards as well as their calculated weight (Table 4).The reason of increasing WQI is considered this region as a drainage system for a groundwater from north toward south.In this study, the groundwater quality may improve due to inflow of freshwater of good quality during rainy season.The high value of WQI at this study has been found to be mainly due to the higher values of EC, TDS, sulphate, chloride, calcium and magnesium where it was found that there is a very high correlation coefficient between them (Table 7).The degree of a liner association between any two of the water quality parameters, and water quality parameters with WQI as measured by the simple correlation coefficient (r) is presented in Table 7. Correlation analysis measures the closeness of the relationship between chosen variables.If the correlation is nearer to +1 or -1, it shows the perfect linear relationship between the two variables.This way analysis attempts to establish the nature of the relationship between the water quality parameters and WQI.It is observed that the EC variations are mainly controlled by total dissolved solids (r=0.994** ), chloride (r=0.739** ), potassium (r=0.806** ), magnesium (r=0.844** ) and calcium (r=0.796** ).Calculated WQI also show that the highly significant interrelated with the values of EC (r=0.958** ), TDS (r=0.973** ), Cl (r=0.793** ), K (r= 0.929 ** ), Mg (r=0.890** ) and Ca (r=0.669 * ).

CONCLUSIONS
In the present study water quality index has been computed to assess suitability of groundwater quality for drinking purposes in Amara city.Twelve groundwater samples were collected to comprehensive physic- /© 2024 The Authors.Published by Academic Journal INC.This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/bync-nd/4.0/)

Fig. 1 :-
Fig.1: Map of study locations All water samples were collected in acid washed 200 ml polyethylene bottles (5 liter) to prevent unpredictable changes in characteristic as per standard procedures (APHA, 2017).Ten parameters were analyzed for WQI such as pH, EC, TDS, NO 3 -, SO 4 2- /© 2024 The Authors.Published by Academic Journal INC.This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/bync-nd/4.0/) -publishing.com2833-5376 /© 2024 The Authors.Published by Academic Journal INC.This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/bync-nd/4.0/) /© 2024 The Authors.Published by Academic Journal INC.This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/bync-nd/4.0/)

Table 1 .
Location and coordinates of studied groundwater samples

Table 3 .
Water quality classification based on WQI value

Table 2 .
Physiochemical properties of groundwater samples in study area ISSN:

Table 4 .
An example Calculation of WQI for the sample 1 (GW1) ISSN:

Table 7 :
Correlation coefficient matrix of water quality parameter and WQI