The Influence of the Tigris River Discharge on the Hydrochemistry with Time, from Baghdad to Amara, Southern Iraq

Received: 28 February 2022 The Tigris River discharge is constantly changing as a result of climate variations. Water flow differences will influence the water quality, the hydrochemistry and water type through time. Hence, evaluation of the relationship between the water flow,and the hydrochemistry with time is vital. The climatological data was studied for Baghdad, Kut, Ali Al Gharbi and Amara meteorological stations for 1990-2020. The data of this study covers annual flow conditions of the Tigris River, the total dissolved solids, and the main ions on monthly bases for the period 2005-2021 for the four sites: Baghdad , Kut , Ali Al Gharbi and Amara. These data were used to establish the relationships between water discharge (m/sec) with total dissolved solids (mg/l) and main cations (Na, Ca, Mg, and K) and anions (Cl ̅, SO4, HCO3). The climatological data for 1990-2020 show that the annual rainfall values of all sites decreased over time,while, the temperature and the evaporation are constantly increasing due to the climate change effects over the years. The average annual flow of the Tigris River at Baghdad and Kut sites are 535.9 and 231.8 m/sec respectively. While for Ali Al Gharbi and Amara sites are with an average of 183.99 and 68.7 m/sec respectively. The mean annual total dissolved solids averages are 664.7 and 759.09 mg/l for Baghdad and Kut sites respectively. While, for Ali Al Gharbi and Amara sites are with an average of 1066.1 and 1189.2 mg/l respectively. The decrease in the Tigris River discharge affects the chemistry. Calcium, magnesium, and sulfate ions in Baghdad and Kut sites are dominated. While at Ali Al Gharbi and Amara, sodium and sulfate ions are dominant. Such variation is related to the decrease in the Tigris River discharge and the effect of the dissolution of ions. Moreover, the entry of the transported dissolved load, the city’s sewage, and the agricultural lands’ water that flows into the river increase as the transportation distance increase from Baghdad to Amara. Accepted:


Introduction
The growing concern over human-induced global warming has brought out serious discussions about the correlation between precipitation intensity and surface temperature. Iraq is currently exposed to climate changes, as these climatic changes have led to a shortage of rainfall in Iraq, affecting the rate of discharge of the Tigris River negatively Adamo et al., 2018;Ibrahim and Al-Dabbas, 2021). The population growth, arid climate, agricultural and industrial development have increased the stresses on the water resources. The Tigris River is a dynamic system with a state of continuous change. It needs successive studies to notice the changes through time due to the construction of dams, climate change impact, the use of irrigation water, and Population growth. Typically, policy discussions and scientific studies today omit the important linkages between water quality and climate change. Iraq has already experienced drought due to climatic change, which would impact the Tigris River water quality. These climatic changes also affected the yearly discharge of the Tigris River; many water infrastructure projects were implemented in the river basin in Turkey. The annual mean Tigris River discharge was 672 m3/s at the Iraqi -Syrian border from 1960to 1984, decreased to 596 m3/s between 1985and 2008 and became lower to about 413 m3/s during the recent years. Such situation has caused vital problems in the Tigris basin and deterioration in water quality especially at the downstream of the river in southern Iraq Al-Rawi, 2005; Al-Ansari, 2019; Hameed et al., 2018). Actually, the Tigris River is exposed to numerous pollution processes, such as hazardous materials such as pesticides and fertilizers as well as the drain of irrigation water are also discharged to the river. Actually these anthropogenic inputs such as discharge of sewage, industrial and mining effluents, which are loaded with quantities of organic and inorganic materials in addition to the presence of large numbers of livestock in the villages adjacent to the river (Buday et al.,1980;Jassim and Goff, 2006;Hatat, 2009). Several researches have taken the change in the discharge of the Tigris river at regional or global scales using a variety of approaches, including hydrological modeling, gauge stations data analysis, regression analysis ,but few concentrating on the pollution that causes high risks both to the environment itself and to its inhabiting forms of life Al-Rawi, 2005;AL-Fatlawy;2007;Niewolak, 2000 andWeiner, 2010). Water is polluted when contains materials that makes it unsuitable for different usesresulting naturally, or from human activities (Awadh and Ahmed, 2013). Water quality comprises the physical, chemical and biological criteria of water. Thus, this study attempts to evaluate the environmental pollution and the impact of the climatic change on the hydrochemistry of the Tigris River from the years 2005 to 2021 and it is considered as a novelty of this research, includes four stations from Baghdad, Kut, Ali Al Gharbi and Amara sites. These sites are with elevation 33 to 8 m. a. s. l. and located within latitudes (44º37′48 to 47º63′) and longitudes (33º28′28 to 31º53′). Geologically, the Tigris river course which is about 320 Km in distance from Baghdad and Amara cities, within chosen study area is passing through Miocene Formations (Muqdadiya, Injana, and Fatha formations) that are exposed through its course, with quaternary deposits which composed of evaporates, carbonates and clay sediments that appear along the Tigris River beds southward to Amara city (IMO, 2021;Nada et al., 2019;NCWRM, 2021;Rasheed, and Al-Ramahi, 2021) (Fig.1).
This research objectives are assessment of the annual flow, main ions, trace elements, along the Tigris River from Baghdad, Kut, Ali Al Gharbi and Amara sites, as well as determining the relationship between dissolved loads and discharge over the years 2005-2021.

Materials and Methods
• Historical climatological data, such as rainfall, temperature and evaporation were analyzed for the Baghdad, Kut, Ali Al Gharbi and Amara Meteorological Stations for the period 1980-2020 (Imo,2021) • Historical discharge and hydrochemical data such as TDS, main cations (Na + , Ca 2+ , Mg 2+ and K + ) and anions (Cl‾, SO 4 2-, HCO 3 ‾) of the Tigris River were investigated to indicate the effect of decreasing water flow on the Tigris River water salinity for the Baghdad, Kut, Ali Al Gharbi and Amara sites for the years 2005-2021 (NCWRM, 2021). Independency, stationaryness, and homogeneity were analyzed in the obtained data. These data were used to develop connections between water discharge (m 3 /sec) and total dissolved solids (TDS) (mg/l) and main ions (mg/l) such as major cations (Na + ,Ca 2+ ,Mg 2+ , and K + ) and anions (Cl -, SO4 2-, HCO3 -) in the Tigris River. The hydrochemical analysis were done following the international methods of analyses, (APHA, 1999). The plots reveal an inverse relationship between the rise in water salinity and the decrease in discharge.
Total hardness is analyzed according to Hem, (1985)

Mean annual temperature
Mean annual temperature (C o ) for Baghdad, Kut, Ali Al Gharbi and Amara sites during the years 1980 to 2020 were plotted against time for available data (Fig. 2 a, b,c,d). There is a positive relationship between temperature with time. An increase in temperature values demonstrating from the general trend line of this relation. The results show that the average mean annual temperature values of Baghdad and Kut sites are 23.6C 0 and 24.7 C 0 ,respectively ( Fig. 2a and b). While for Ali Al Gharbi and Amara sites the average mean temperature are 25.8C 0 and 25. 5 C o , respectively ( Fig. 2c and d).

Mean annual rainfall
The average annual rainfall values (mm) are related to time from 1980 to 2020, reflecting a negative correlation (Fig.3 a , b,c,d).The results show that the average values of Baghdad and Kut are 98..4 and 90.9 mm ( Fig. 3a and b). While in Ali Al Gharbi and Amara sites the average values are 124.8 and 181.4 mm ( Fig. 3c and d). The general trend line shows a noticeable drop in rainfall quantities, which is demonstrated from the general trend line due to global climatic change.

Mean annual evaporation
The average annual evaporation (mm) for Baghdad, Kut, Ali Al Gharbi and Amara sites during the years 1980 to 2020 indicated a positive correlation between evaporation and years, with the noticeable increase in evaporation demonstrating this relation general trend line (Fig.2 a

Discharge and Total Dissolved Solids Relationship
The average mean annual TDS of the Tigris River water from 2005 to 2021 are 664.7 and 759.1 mg/l for Baghdad and Kut, respectively. While, for Ali Al Gharbi and Amara are 1066.1 and 1189.2 mg/l respectively. The average mean discharge in the Baghdad and Kut sites are 535.96 and 135-367 m 3 /sec, respectively (Fig.5 a and b). While in Ali Al Gharbi and Amara sites the average discharge values are 183.99 and 68.7 m 3 /s respectively (Fig.5 c and d). The TDS concentration is correlated inversely with discharge; the high discharge rates act as a dilution agent, therefore; the strength of the solute becomes less when the discharge increase. The correlation between water salinity as TDS concentrations and their variation with discharge rates is beneficial for improving water quality. The general trend line reveal an inverse relationship between the rise in water salinity and the decrease in discharge (Fig.5 a,b,c,d).

3.TDS-Electrical Conductivity
The Electrical conductivity (EC) is essential water quality parameter demonstrates the ability of electrical current in water to demonstrate the salinity as TDS. This number is proportional to the TDS and is determined by the presence of ions (TDS). Increases in sulfate, chloride, sodium, potassium, calcium, and magnesium in water increase the EC, leading to deteriorate the water quality (Al-Ali and Al-Dabbas, 2021; Awadh and Al-Ghani, 2014). The Tigris Rivers annual average EC ds/m readings in Baghdad and Kut sites are ranging from ( 0.59-2) and (0.78-1.9) ds/m, with average mean values of 0.99 and 1.14 ds/m, respectively. While in Ali al Gharbi and Amara sites are ranging from 1.7-2.8 and 1.1-3.2 ds/m with average mean values of 1.63 and 1.83 ds/m, respectively (Fig.6 a, b,c,d).

Dissolved Loads Calculation
The link between monthly discharge and monthly dissolved loads transported through a given gauging station was determined using the rating curve. The results revealed a direct relationship between discharge and loads (Al Bomola, 2013;Hamad, 2015).The Average monthly dissolved loads for the current study from 2005 to 2020 are 0.87, 0.44, 0.48, and 0.21 million tons/ month for Baghdad, Kut, Ali Al Gharbi and Amara sites, respectively (Fig.7 a, b, c, and d).
Moreover, there is a temporal variation in TDS concentration and dissolved load, this result is agreeing with Saleh ,(1982) ;Awwad, (1997), and Ghliem, (1997), that there is a seasonal variation in the concentrations, which correspond to the high suspended and dissolved loads during dry seasons. A comparison between the average and ranges of dissolved loads of the current study with the previous studies reflect that the results of the current study came close to the loads calculated from the previous studies of Saleh ,(1982) ;Awwad, (1997), and Ghliem, (1997), with relative decrease in the current study loads ranging between 0.02%-0.36% which may be results from the decrease in the discharge rates.

Major Ions and Total Dissolved Solids Relationship
The results of the mean values of the major anions and cations and TDS are tabulated in Table 1.

TDS-Ca 2+ correlations
Carbonates, silicates, and evaporates are the main sources of Ca 2+ dissolved in water. The Annual averages of Ca in the Tigris River are 73.004 and 84.9 ppm for the Baghdad and Kut sites, respectively ( Fig. 8a and b). While, in Ali Al Gharbi and Amara sites are 96.55 and 94.8 ppm respectively (Fig.8 c  and d).

3.5.2.TDS-Mg 2+ correlation
Limestone and dolomite are the main sources of Mg 2+ , High magnesium may be a result of soil erosion (Al-Ali and Al-Dabbas, 2021). Magnesium annual average values in the Tigris River are 46.05 and 50.1 ppm for the Baghdad and kut sites, respectively ( Fig.9.a and b). While in the Ali Al Gharbi and Amara sites are 61.13 and 68.1 ppm, respectively (Fig.9.c and d).

TDS-Na + correlation
The presence of sodium salts in the feeding areas through agricultural areas, evaporation process, and man-made activities resulted in considerably high sodium over the research period, which is responsible for general water quality deterioration. A positive correlation resulted from plotting Na + ppm with TDS ppm in the Baghdad, Kut, Ali Al Gharbi and Amara sites for 2005 to 2021 (Fig.10  a,b,c,d). Na + average values in the Baghdad and Kut are 74.1 and 88.5 ppm.While, in Ali Al Gharbi and Amara sites are 177.2 and 205ppm ,respectively.

TDS-K + correlation
The main sources of K in river are the clay minerals and fertilizers (Semwal and Jangwan,2009). The K annual average values in the Tigris River in the Baghdad and Kut sites are 3.9 and 4.09 ppm, respectively. While in the Ali Al Gharbi and Amara sites are 4.9 and 5.12 ppm, respectively (Fig.11a,  b, c, d).

TDS-SO4 2correlation
The pollutants dumped in the river as well as the evaporates, carbonates and shale are the main sources of dissolved sulfates in water (Jun Cai et al., 2008;Nada et al., 2019). The SO4 annual average values of the Tigris river in the Baghdad and Kut sites are 267.5 and 318.5 ppm, respectively. While, in the Ali Al Gharbi and Amara sites are 381.5 and 411.75 ppm , respectively (Fig.12 a,b,c,d).

TDS -Clcorrelation
The main sources of Cl in river are the halites and the anthropogenic wastes (Semwal and Jangwan,2009).A positive relation of Clwith TDS is indicated. The Cl annual average values of the Tigris River in the Baghdad and Kut sites are 81.3 and 103.5 ppm respectively. While, the Cl in the Ali Al Gharbi and Amara are 233.5 and 275.7 ppm, respectively (Fig.13a,b,c,d).

TDS-HCO3correlation
Actually, the values of HCO3 are depending on rainfall and river discharge water (Jun Cai et al,2008).The HCO 3 annual average values of the Tigris River in the Baghdad and Kut sites are 156.13 and 161.3 ppm, respectively. While, in the Ali al Gharbi and Amara sites are 163.34 and 158.6 ppm ( Fig.14.a,b,c,d).

TH -Mg 2+ ,Ca 2+ Correlation
Water total hardness (TH) is caused by Mg 2+ and Ca 2+ disolved ions (Al-Ali and Al-Dabbas, 2021). The Tigris Rivers annual mean average value of TH in the Baghdad and Kut sites are 379.5 and 421.44 ppm,respectively. While, in the Ali al Gharbi and Amara are 493.8 and 544.8 ppm,respectively (Fig.15 a, b,c,d).

Trace Elements
The trace elements in natural water are defined as those with a concentration of less than 1 ppm, which suggests that their amounts are insignificant when compared to the total main ions. The following trace elements, Cu, Cd, B, Fe, Cr, and Pb were investigated. The Tigris Rivers annual averages of Pb are 0.031 and 0.016 ppm for the Baghdad and Kut sites respectively, whereas in the Ali al Gharbi and Amara are 0.058 and 0.068 ppm respectively. The annual averages of Fe in the Baghdad and Kut sites are 0.056 and 0.058 ppm, whereas in the Ali al Gharbi and Amara sites are 0.005 and 0.0615 ppm respectively. The annual averages of B in the Baghdad and Kut sites are 0.244 and 0.308 ppm respectively ,whereas in the Ali al Gharbi and Amara are 0.312 and 0.33ppm respectively. The annual averages of Cu in the Baghdad and Kut sites are 0.049 and 0.032 ppm respectively, whereas in the Ali al Gharbi and Amara are 0.05 and 0.043ppm respectively. The annual averages of Cr in the Baghdad and Kut sites are 0.015 and 0.0212 ppmrespectively, whereas in the Ali al Gharbi and Amara sites are 0.087 and 0.033 ppm respectively. The annual averages of Cd in the Baghdad and Kut sites are 0.0195 and 0.005 ppm respectively, whereas in the Ali l Gharbi and Amara sites are 0.006 and 0.007ppm respectively. The results reflect that all the concentrations of these trace elements along the Tigris River are below permissible limits when comparing the trace elements with WHO, (2008) standards.
The source of these trace elements may be from anthropogenic inputs into soils from different sources, such as agricultural fertilizers, atmospheric deposition, traffic emission, and sewage sludge (Oleiwi and Al-Dabbas ,2022). In general, it is believed that the analyzed trace elements are controlled by parent or source rocks, climatic conditions, pyogenic processes, and drainage where the soils and surface sediments of Mesopotamia terrains are immature with little modifications or alterations by pyogenesis and have undergone degradation by fluvial processes. Salinization of the upper part of the Mesopotamia sediments is induced by poor drainage, little rainfall, and very high evaporation rates. The Major ions and trace elements concentration in the surface water appear to have been mainly influenced by the type of source rocks of the Tigris River and its tributaries (Oleiwi and Al-Dabbas ,2022).

Hydrochemical Formula of the Tigris River
The type of water varies from time to time during the study period. The formula of water classification depends on the ratio of the main ions expressed by epm % units which has more than 15% availability. The cations are at the base of the equation, while anions are above, pH and TDS values are in both sides, as shown in eq (3).
The water formula of the Tigris river for 2005 to 2021 is Mg+2-Ca+2-Na+-SO4-HCO3-at Baghdad classified as: MgSO4 -water type ,while it is of Ca+ -Mg2+ -Na2+-SO4-Cl at Kut and classified as: CaSO4-water type, at the Ali Al Gharbi and Amara sites, the water formula is Na + , Mg 2+ , Ca 2+ ,SO4-Cl, for both sites and classified as NaSO 4 -water type.
This finding may reflect the Tigris water's deterioration with time due to climate change effects, low river discharge, and relatively high contamination within the past decades. The salinity varies within the studied sites depending on nature, geographic location, and the affected factors within each site, such as soil variation, agriculture and population density …etc. Accordingly, it was noticed that the salinity within the Amara site is higher than that of the Baghdad site, and the main ions behave the same as the salinity.
Moreover, the high salinity values indicate the high pollution loads related to the input of untreated wastewater directly into the river and pouring the contaminated surface drainage from irrigation, industrial and domestic activities.

Discussion
Climate change has a direct impact on discharge rates in the Tigris River. As indicated by the decrease of the discharge rates and average annual rainfall with time. Consequently, the water salinity of the Tigris River is rising, and the water quality is deteriorating. The high TDS and EC readings clearly suggest significant pollution loads, which are associated to high evaporation rates and limited water flow, in addition of pouring the wastewater into river without treatment. The results reflect that there is a significant rise in TDS and that the water quality has changed from Ca-SO4 and Mg-SO4 in Baghdad and Kut to Na-SO4 at both sites of Ali AL Gharbi and Amara due to relative pollution of sewage water and the irrigation water of the agricultural lands.The salinity varies within the studied sites depending on nature, geographic location, and the affected factors within each site such as: soil variation, agriculture and population density …etc.
The results are compared with the previous researches showed that the River salinity concentration and the major ions have increased in the river water more than before year 2005 due to the relatively low flow in the river within the last decades that caused by the global climate change (Table 2) (Saleh , 1982;Al-Azzawi , 1996;Awwad,1997;Ghliem ,1997). Moreover, it is believed that the average mean annual water type detoriorated due to the climate change that caused in rainfall rareness and high rates of temperature degrees. sewage water and the drainage water of the agricultural lands that flow into the river without treatments.
• It is noted that there is an increase in the water salinity toward the south. The high concentrations of TDS and EC values clearly indicate the high pollution loads that are related to the high evaporation rates and limited water discharge, throwing the untreated wastewater directly into the river as well as pouring the contaminated surface and subsurface drainage from irrigation, industrial and domestic activities. • The dissolved loads are increased depending on the discharge rates.They are changing temporally and spatially, as the river loads were directly affected by TDS accumulation from Baghdad to Amara sites. • The Tigris River water type in Baghdad is magnesium-sulfates and in Kut is calciumsulfates.
But in both Ali Al Gharbi and Amara sites is sodium-sulfates. • By comparing the hydrochemical analysis results of present study with the studies before year 2005 reflecting salinities relatively lower than the current study during the nineties of the last century. • There is a strong effect of global climate warming on the Tigris River discharge and its water quality.