Iraqi Geological

Abstract


Introduction
Worldwide, more than a third of all water used by humans comes from groundwater.In rural areas, the percentage is even higher: more than half of all drinking water worldwide is supplied from groundwater (Harter, 2015).Continuing groundwater extraction from the aquifers for all purposes, lead to groundwater depletion in many parts of the world (Ramesh and Fritz, 2016).Groundwater hydrology is the subdivision of the science of hydrology that deals with the occurrence, movement, and quality of water beneath the Earth's surface.The quality of groundwater is no less important than its quantity (Al-Kubaisi and Al-Kubaisi, 2022).Estimating the physical properties of water-bearing layers is an essential part of groundwater studies.Environmental problems arise as a result of wasting water and not treating wastewater, and this indicates a low environmental feeling for society (Awadh, 2018).Recently, water consumption has increased rapidly with the increase in water demand for developing industry and building energy, abundant agriculture, keeping pace with urbanization, improving livelihood, and constructing a livable environment.Our daily life requires more attention in evaluating water and its suitability for different expediency purposes (Al-Kubaisi, 2020).Particular investigations to comprehend the hydrochemical characteristics of groundwater and their development, not only assist save groundwater as a worthy resource and its utilization, but as well provide insight into alteration in the water ecology (Lawrence et al., 2000;Edmunds et al., 2006).Groundwater is influenced by climate alteration which, in turn, impacts the quality of water and the potential of using it for different purposes, (Al-Kubaisi and Al-Kubaisi, 2018).Geologically, the formations will affect the chemistry of the groundwater, so it is necessary to know the formations located in the study area.The area was characterized by the existence of different formations belonging to Oligocene to Recent periods.Anah, Euphrates, and Fatha formations are belonging to the Upper Oligocene, Lower Miocene, and Middle Miocene respectively, as well as Quaternary sediments (Jassim and Goff, 2006).Various diagrams and their representations can be used to comprehend the variations in chemical nature and hydrochemical facies of groundwater by using anions and cations concentrations.The study is a try to explain the disparity in hydrochemical facies through the implementation Piper (three-line) diagram.furthermore, groundwater in the study area is evaluated for numerous purposes..

Study Area
The study area is located in the northeastern part of Al-Anbar Governorate, within the lower valleys region, at the west bank of the Euphrates River, and geographically between latitudes 34º 1′ -34º 6′ N and longitudes 42º 16′ -42º 25′ E. The study area extends between Al-Khasfa area and Alus village, south of Haditha city, bounded from the north by Haditha City, from the south by Banat Al-Hassan valley, and from the east by the Euphrates River (Fig. 1).

Fig. 1. Location of the study area
The total area is about 120 km 2 .The maximum height is 168 m a.s.l.near Alkhasfa Area, and the minimum height is 111 m a.s.l. in Alus village.The study area is a portion of the Western Desert and Western plateau that is characterized by the domination of an arid climate.The total annual rainfall was 130 mm and the highest temperatures were in July 35.1 ºC, while the lowest temperatures were in January as they reached 8.3 ºC.Therefore, the nature of the prevailing climate was also reflected in the nature and quantity of rainfall, as well as the winds that have a great influence on population stability and agricultural activities.

Materials and Methods
Eighteen groundwater samples were collected spread in the study area, Fig. 2).The polyethylene bottles were used to collect these samples during October 2021 for hydrochemical analyses.The measurements were taken in situ for the water samples using the specialized device.These measurements are pH, TDS in mg/l, EC in μS/cm, and temperature in C°.This procedure is to determine the change that may occur in the chemical properties compared to the results of the laboratory analysis that will be conducted after a certain period.. Using standard methods and analytical methods that are recommended by APHA, 2005.The samples were conveyed to the market research & consumer protection center lab for the examination of the cations and anions.The charge balance error (CBE) was used to verify the accuracy of the results for the major ions (cations and anions) data, which were calculated according to the following Eq. 1.

CBE% = |
∑ cations (meq/l) − ∑ anions (meq/l) ∑ cations (meq/l) + ∑ anions (meq/l) |  100 (1) CBE was calculated for all chemical ions (cations and anions) data and all results were within permissible limits (less than 5%) (Hounslow, 1995).The Rock Ware-16 software was used to plot a piper diagram.Irrigation parameters (EC, TDS, Sodium percentage (Na%), Sodium Absorption Ratio (SAR), Residual Sodium Carbonate (RSC), and Permeability Index (PI)) were calculated for eighteen samples distributed in the study area to assess their potential for agricultural use, while the water quality index (WQI) was applied to it to assess their potential for human use based on World Health Organization (WHO) standards (WHO, 2011).

Physico-chemical parameters
The Physico-chemical results for groundwater samples of the study area are shown in Table 1.In the study area, the average contribution of cations in the study area was calcium (Ca 2+ ) 15%, magnesium (Mg 2+ ) 6%, sodium (Na + ) 15%, and potassium (K + ) 1%, and anions contribution is chloride (Cl -) 29%, sulfate (SO4 2-) 34% and Alkalinity or Bicarbonates (HCO3 -) (12%) (Fig. 3).These results indicated that cations have dominant ion sodium (Na+), while the sulfate (SO4 2-) is the dominant ion of the groundwater in the study area.The results also showed that all the groundwater samples exceeded the acceptable limit for drinking water recommended by IQS (2009) and WHO (2011).The minimum and maximum values of pH were 7.2 and 7.8 respectively, with an average of 7.4 and these values do not exceed the permissible limits (6.5-8.5)(IQS, 2009;WHO, 2011).High Electrical conductivity (EC) refers to the enrichment of salts to substances dissolved in water, which is a measure of the ability to conduct an electrical current.The average EC was 5126 μS/cm, with a minimum and maximum of 3380 μS/cm and 8380 μS/cm respectively.According to EC values, the water can be classified into three types: Type I, if the EC < 1500 μS/cm (the enrichments of substances dissolved in water are low); type II, if the EC between 1500 and 3000 μS/cm (the enrichments of substances dissolved in water are medium); and type III, if the EC >3000 μS/cm (the enrichments of substances dissolved in water are high); (Subba et al., 2012).Accordingly, all the groundwater samples are from the third class (type III) (the enrichment is high in salts) in the study area.
TDS ranged from 2202 to 7385 mg/l with an average of 3357 mg/l.According to TDS values, the water can be classified into four types: Type I, if the TDS <1000 mg/l (freshwater); type II, if the TDS between 1000 mg/l and 10,000 mg/l (brackish water); type III, if the TDS between 10,000 mg/l and 100,000 mg/l (saline water); and type IV, if the TDS >100,000 mg/l (brine water) (USSL, 1954), therefore, all samples are brackish water.The samples showed EC and TDS values do exceed the permissible limits (1500 μS/cm and 1000 mg/l) (IQS, 2009 andWHO, 2011).The average temperature of groundwater was 28.4°C (varied from 26.1°C to 30°C).The average TH was 2375.5 mg/l, with a minimum and maximum value of 1682.2 mg/l and 3006.3 mg/l respectively, within the impermissible limits of 500 mg/l (IQS, 2009;WHO, 2011).

Hydrochemical Facies
In the fields of hydrogeology and groundwater analysis, and for visualizing the relative abundance of common ions in water samples and grouping them by groundwater facies and other criteria, there is a need to use specialized diagrams for the purpose of achieving a better perception of the water situation in an area.Piper plots (also known as trilinear diagrams) represent very powerful tools in this field where it allows to plot multiple samples on the same plot, (Pipar, 1944).Eighteen samples belong to class 1 (Ca 2+ , Mg 2+ , Cl -and SO4 2-) and category I (SO4 2--Cl -and Ca 2+ -Mg 2+ ), permanent hardness (calcium chloride type) for the waters of the study area (Fig. 4) and (Table 2).

Hydrochemical facies Class
Water type Category

IV
Mixing zone (no one anioncation exceed 50 %) V

Suitability as irrigation water
The growth of crops and their productivity is affected by numerous water quality parameters, and the mineralization of water and its effect on soil and plants is an indicator of the suitability of groundwater for irrigation.Numerous studies confirm the importance of irrigation water quality parameters such as TDS, EC, Ca 2+ , Mg 2+ , Na + , Cl -, SO4 2-, HCO3 -, SAR, Na%, RSC and PI (Raghunath, 1987;Ravikumar et al., 2011;Ravikumar and Somashekar, 2013).In this study, many parameters were used such as EC, TDS, Sodium Absorption Ratio (SAR), Sodium percentage (Na%), Residual Sodium Carbonate (RSC), and Permeability Index (PI).Eighteen samples of the study area are unsuitable for irrigation in general based on TDS (ranged from 2202 to 7385 mg/l), EC (ranged from 3380 μS/cm to 8380 μS/cm), SAR (ranged from 3.73 to 6.72), percent sodium (ranged from 29.12 to 38.83), RSC (ranged from -64.57 to -18.07), and PI (ranged from 37.3 to 42.54).Turgeon (2000) has classified irrigation water based on the EC values as seen in Table 3 to (C1) low, (C2) medium, (C3) high, and (C4) very high salinity zones.Based on this classification, the groundwater of the study area for period was very high saline (C4) in all wells is generally unacceptable for irrigation, except for very salt-tolerant plants, excellent drainage, frequent leaching and intensive management.Wilcox (1948) classified groundwater for irrigation purposes depending on the values of SAR.According to this classification, all groundwater samples are of class S1 (Use on sodium sensitive crops) (Table 4).Don (1995) irrigation water was classified basis on (Na%) (Table 5).The groundwater samples were of class "good" as an irrigation water.(Don, 1995)

Range
Water quality < 1.25 Good 1.25 -2.5 Medium >2.5 Bad Based on the permeability index (PI), Doneen (1964) developed an evaluation criterion suitability of water for irrigation (Table 7).,2,3,4,5,6,7,8,9,10,11,12, 13,14,15,16,17,18 Good quality for irrigation Class-III >75 ---Unsuitable for irrigation Doneen (1964) has divided this classification, the Permeability Index (PI) values less than 25% fall into Class-I and Class-II includes PI values that range between 25% and 75% are classified good irrigation, as for Class-III includes PI values greater than 75% is unsuitable for irrigation (Nagaraju et al., 2006).Based on this classification, results indicate that the groundwater in the study area is under class-II, which represents 25% -75%, which considered as good quality for irrigation.Based on all of the above, groundwater in the study area is generally suitable for use as irrigation water.

Suitability as drinking water
The calculation of the Water Quality Index is to facilitate the judgment of water type by converting the vast amount of complex data into information that is easy and understandable.The Water Quality Index (WQI) is a primary indicator of water type because it gives a general idea of potential water problems in any area.The average period (October, 2021) is compared with the Iraqi quality standard IQS (2009), andWorld Health Organization Standard WHO (2011) to determine its suitability as drinking water in the study area Table (8).The results approved that groundwater in the study area is unsuitable for human drinking purpose because they are exceeding the permissible limits, where in the case of suitable one element, there is another element that is not suitable.

Exchangeable During the Residence Time
The distribution and occurrence of ions in water depend on the geochemical reactions that control it (Al-Kilabi, 2018).By studying the Chloro-Alkaline Index (CAI), the ion exchange between water and the host environment can be understood during residence or travel time.
To show the ion exchange between the water and the host's environment, (Schoeller, 1965) proposed the two chloro -alkaline indicators CAI 1 and CAI 2. The two chloro -alkaline indexes were confirmed by using the following equations 2 and 3.
(3) Generally, the Chloro -Alkaline Index values are positive (+) or negative (-).When the values are positive, the basic exchange is the exchange of sodium (Na + ) and potassium (K + ) ions in water with magnesium (Mg 2+ ) or calcium (Ca 2+ ) ions in materials exposed to weathering.And vice versa, when the values are negative, the basic exchange is the inverse exchange of ions.The CAI 1 values range from 0.07 meq/l to 0.48 meq/l with a mean of 0.42 meq/l while CAI 2 range from 0.01 meq/l to 0.37 meq/l with a mean value of 0.27 meq/l.All the results of CAI are positive, thus indicating the exchange of sodium (Na + ) and potassium (K + ) ions from the water with (Mg 2+ ) and calcium (Ca 2+ ) of the weathered material (host rocks).To understand the chemical composition of groundwater in the study area, the above indicator was applied, as the results indicated the basic exchange of ions between the groundwater and its host materials.

Conclusions
From the study, it is concluded that water of the study area belongs to calcium chloride type (permanent hardness and non-carbonate hardness exceeds 50%).It is characterized by a slightly alkaline water samples, brackish water, and high enrichment salts, within the impermissible limits of the WHO standards.The average contribution of cations in the study area was calcium (Ca 2+ ) (13%), magnesium (Mg 2+ ) (5%), sodium (Na + ) (14%) and potassium (K + ) (1%), and anions contribution is chloride (Cl -) (25%), sulfate (SO4 2-) (30%) and Alkalinity or Bicarbonates (HCO3 -) (12%).Piper diagram illustrated 18 samples belong to class 1 (Ca 2+ , Mg 2+ , Cl -, SO4 2-) and category I (SO4 2--Cl -and Ca 2+ -Mg 2+ ), permanent hardness (calcium chloride type) for the waters of the study area.Overall the samples of the study area belong to a brackish water class of TDS, the enrichment is high in salts to the impermissible class of EC, no problem of SAR, good of Na%, safe for irrigation of RSC and PI.WQI of the study area was found to be unsuitable for human drinking purpose because they are exceeding the permissible limits, where in the case of suitable one element, there is another element is not suitable.The Chloro-Alkaline Index (CAI) showed the exchange of sodium (Na + ) and potassium (K + ) ions from the water with magnesium (Mg 2+ ) and calcium (Ca 2+ ) of the host rocks.

Fig. 2 .
Fig. 2. Location of the sampling location of 18 stations

Fig. 3 .
Fig. 3.The Pie diagram displays the average ionic constituents in the study area

Fig. 4 .
Fig. 4. Piper diagram for groundwater samples that show hydrochemical facies in the studied area

Table 1 .
Results of the physicochemical properties analysis of groundwater samples.

Table 2 .
Classification of groundwater samples according to Piper trilinear diagram

Table 5 .
Irrigation water classification based on (Na %) values

Table 8 .
Comparing groundwater Samples with the standards of Drinking Water(WHO, 2011 and  IQS, 2009)