Water Quality Monitoring of Tigris River by Using (GIS)-Based Physicochemical Parameters in Baghdad, Iraq

Water quality deterioration has become an essential concern worldwide due to climatic changes and increased pollution. As a result, the available drinking water supply resources will receive its ration of this deterioration. This study was conducted to monitor the water quality of the Tigris River in eight different locations in Baghdad during the period between 2005 and 2013. Water samples were collected and analyzed for fourteen selected physicochemical parameters including alkalinity, total hardness (TH), turbidity, total suspended solids (TSS), temperature, pH, nitrate, nitrite, phosphate, electrical conductivity (EC), chloride, calcium, magnesium, and sulfate. To show the spatial and temporal variations of the selected parameters along the study area easily and objectively, Geographical Information System maps (GIS maps) were used. Results showed that the obtained values in winter of alkalinity, turbidity, electrical conductivity, and the concentration of calcium, magnesium, sulfate, nitrite, phosphate, chloride, and total suspended solids were higher as compared with the corresponding values in summer. On the other hand, temperature, total hardness, pH, and nitrate values were higher in summer as compared with the corresponding values in winter. The water quality of Tigris River throughout the study period was within the permissible limits of the Iraqi standards for drinking water.


Introduction
Water, the main constituent of ecosystem is a precious national asset and a prime natural resources may be in the form of rain water, ground water, surface water (i.e. rivers, lakes, seas, etc.), and glaciers. The surface water is the most important forms of water for human activities such as drinking water, agriculture, industry, hydropower generation and other various sectors of the economy. In the world, one of the most primary environmental issues is water quality deterioration that resulted from the climatic change and increased pollution (Palmer and Bernhardt, 2004). Growing attention had been noticed during the last decades concerning water quality assessment of different rivers by analyzing the physicochemical and biological parameters of water and monitoring the spatial and temporal variations. Rani et al. 2011, studied the water quality of three rivers in terms of temporal variations and they found that the anthropogenic activities influencing the water quality of the studied surface area round the year. Basu and Lokesh, 2013, studied the temporal and spatial variations of River Kabini and they represented temporal variations by box plots. The study concluded that the river was rampantly polluted due to anthropogenic sources. Subin and Husna, 2013, assessed the water quality of Periyar river lets by assessing the impact of waste discharge at four selected sites. The study showed that the pollution load resulted from the disposal of solid waste into the river in addition to discharge of industrial and sewage waste. In Nigeria, Mustapha et al.2013, assessed the water quality of Jakarta River Basin by using the environmental techniques. The study established a strong relationship between BOD5 and COD and salinity and turbidity controlling the linear effects of NH4 and conductivity respectively. A paper dealt with water quality management in terms of monthly variations was presented by Parmar and Bhardwaj, 2014. The paper predicted that the estimation of future water quality parameters values can be done by using auto regressive integrated moving average model. Thomas et al. 2014, conducted a study to understand the impact of geochemical processes and other processes on the water quality of Muthirapuzah River. The study suggested seasonality over the hydrochemical composition. In 2017, Sharma et al. assessed the pollution of Yamuna River in terms of water quality using Geographical Information system (GIS). The study showed that the water river in Delhi is unsuitable for the human uses. This study aims to monitor the water quality of the Tigris River in Baghdad, Iraq by using the technique of a geographic information system (GIS). This technique allows creating parameter maps for easy and objective visual interpretation of the spatial and temporal variations for the obtained physicochemical data.

Materials ad Methods
Baghdad, the capital of Iraq 33° 20′ 0″ N, 44° 23′ 0″ E is located along the Tigris river. It is the largest city in Iraq according to its population in 2016 which was 8765000. The density of population and presence of many industries with their wastewater which discharged to the river in addition to different agricultural activities make the possibility of deterioration of its water quality is an indispensable fact. Therefore; monitoring of the Tigris River in this area is very important. Our study was conducted to cover eight different stations along the river starting from Al-Karkh, Shark Dijlah, Al-Karama, Al-Wathba, Al-Qadsya, and Al-Doura station. The water samples were collected during winter and summer seasons from the Tigris River for the period between 2005 and 2013 and analyzed in the laboratories of Baghdad Government according to the method adopted by American Public Health Association (APHA) for water and wastewater standards (APHA, 1998). The selected parameters were alkalinity mg/L as CaCO3, total hardness (TH) mg/L as CaCO3, turbidity NTU, total suspended solids (TSS) mg/L, temperature ºC, pH, nitrate mg/L, nitrite mg/L, phosphate mg/L, electrical conductivity (EC) µs/cm, chloride mg/L, calcium mg/L, magnesium mg/L and sulfate mg/L. In order to determine its suitability for drinking water, the obtained results were compared to the upper permissible limits recommended by Iraqi standard specification for drinking water No.417, modification No.2 of 2009 shown in table 1. To show the spatial and temporal variations of the obtained physicochemical data easily and objectively, the technique of a geographic information system (GIS) was used.

Results and Discussion
Total suspended solids and Electrical Conductivity: The TSS parameter is considered a reliable and up-to-date measurement of the status of water resource quality to the decision makers in the water quality management field. The seasonal variation in TSS and EC are shown in fig.1 and 2 respectively. In this study, the TSS in summer ranged between 76.95 and 123.99 mg/L, while in winter ranged between 58.925 and 176.889 mg/L. As can be noted from the figure, the minimum value appeared at Al-Karkh station throughout the study period, while the maximum value appeared at Shark Dijlah station during winter. The high value of suspended solids may be due to high levels of overland, debris flows, mass wasting, and high stream erosion (Davie, 2002, Moore et al. 2009). On the other hand, the electrical conductivity is used to measure the salinity of the water. The EC of river water ranged from 605.656 to 797.382µs/cm in summer and 686.259 to 974.898µs/cm in winter. As shown in fig. 2, the values were increased as the river moved downwards because of increasing the domestic sewage waste, the agricultural and industrial activities in the region. The maximum values were recorded in winter as the erosion process of the sedimentary rocks increased and then the interference between groundwater and surface water appeared. These values show no abrupt spatial and temporal changes and the tendency of the Tigris river is towards alkaline nature. The maximum value was recorded during summer and it may be due to a high biological activity of the river (saravanakumar et al., 2008). The values of pH throughout the study period were within the permissible limits that recommended by the Iraqi standards.  shows that total hardness ranged from 130.451 to 152.909 mg/L as CaCO3 in winter and 235.802 to 301.146 mg/L as CaCO3 in summer. Throughout the study period, the least values were observed at Al-Karkh station, while the highest values were noted at downstream stations which may be attributed to the direct pollution caused by anthropogenic activities or from the natural accumulation of salts enter from contact with the geological formation and soils as well as the increase of evaporation at high temperature. The values of total hardness throughout the study period were less than the upper permissible limits that recommended by the Iraqi standards.

Fig. 5: Spatial and temporal variation in total hardness
Alkalinity: It is a measure of the water's capacity to neutralize acids. Minerals such as limestone are responsible to produce alkalinity. High pH values of water indicate the presence of carbonate, bicarbonate, and hydroxides. The main potential source of alkalinity is the natural processes of rock weathering. Alkalinity ranged from 131.001 to 149.542 mg/L as CaCO3 and 130.451 to 152.909mg/L as CaCO3 during summer and winter seasons respectively as shown in fig. 6. The highest value was recorded at Shark Dijlah station during winter, while the least value was recorded at Al-Karkh station. The highest value recorded in winter may be due to pollution by untreated domestic sewage and other anthropogenic activities.  Fig. 7 shows that the least value was recorded at Al-Karkh station increased with the flow direction to reach the highest value at Al -Doura station. During winter the high flow conditions occur causing the increase in suspended load carried by the river leading to high values of turbidity. Major Ions: One of the most familiar methods to reveal the nature of weathering is determining the major ion chemistry that is available in river waters. Calcium (Ca +2 ) and magnesium (Mg +2 ) were selected to represent the major cations, whilst chloride (Cl -1 ) and sulfate (SO4 -2 ) were selected to represent the major anions. The concentration of (Ca) ranged from 66.00 to 99.62 mg /L and 58. Minor Ions and Nutrients: Nitrate (NO3), nitrite (NO2) and phosphate (PO4) were selected to represent the minor ions. The excessive concentration of nutrients is an indication of increasing the domestic sewage and other anthropogenic activities and may lead to eutrophication. In our study, concentration of (NO3) ranged from 0.5249 to 0.8400 mg/L and 0.512 to 0.898 mg/L during winter and summer seasons respectively, while the concentration of (NO2) ranged from 0.0046 to 0.0158 mg/L, and 0.0026 to 0.0116 mg/L during winter and summer seasons respectively. The corresponding values of (PO4) were 0.010 to 0.1446 mg/L and 0.0116 to 0.1346 mg/L as shown in fig.9 below. Throughout the study period, (NO2) and (PO4) had the same increasing spatial pattern as the least concentration of them was observed at Al-Karkh station and the value tends to increase as the river flows downwards till it reaches the highest values at Al-Doura station. Also, they had the same temporal pattern as the highest values observed during winter. On the other hand, the concentration of (NO3) increased with flow direction to Al-Qadsya station and then tends to decrease till it reached Al-Doura station. The highest value of (NO3) was recorded during summer. The concentrations of nitrate and nitrite during the study period were within the permissible limits of Iraqi standards.

Conclusion
Monitoring of water resources quality is a matter of great importance as it provides an evaluation of resource status and its suitability for human activities as well as the aquatic system. In the last decades, this field of knowledge witnessed growing attention around the world using different methodologies and aspects. Our study adopted using GIS technique to simplify the overall representation procedure and facilitate the visual interpretation of the spatial and temporal variations for the obtained physicochemical data during the period lasting from 2005 to 2013 along the selected study area. The main conclusions of this study are: Temporally, the obtained values in winter of alkalinity, turbidity, EC and the concentration of calcium, magnesium, sulfate, nitrite, phosphate, chloride, and total suspended solids were higher as compared with the corresponding values in summer. On the other hand, the temperature, total hardness, pH, and nitrate values were higher in summer as compared with the corresponding values in winter. Spatially, most of the high values were observed at the stations downstream and this is may be due to increasing the agricultural and industrial activities as well as the discharges of untreated or partially treated domestic sewage into the river. The obtained values of the selected parameters throughout the study period were within the permissible limits of the Iraqi standards and this is indicating the suitability of the river for drinking water.