The Tigris River is the second-longest river in Western Asia and runs through heavily populated areas, especially in Baghdad city with nearly 8 million inhabitants. The water demand is at its highest levels, nevertheless the Tigris discharge has severely declined in the last decades; combined with the fact that the wastewater quantities are increasing, and the wastewater treatment plants are experiencing a deficiency. Four sites were chosen: the Tharthar-Tigris Canal which is located in the north part of Baghdad city, Baghdad city, the Diyala River conjunction with the Tigris River site, and Al-Azizziyah site in the south of Baghdad city near Kut government, to determine the effect of the decreasing Tigris River flow on the water quality and to identify the sources of pollution. In this research, the used method evaluates the concentration of the contaminants along the course of the Tigris River to determine the source of the contaminants as the novelty of this research. The data include the discharge of The Tigris River, a hydrochemical analysis, such as major ions and trace elements, and biological parameters (BOD5, COD, E. coli bacteria, and coliform bacteria MPN/100 mL) as contamination indicators. Multivariate statistical techniques (factor analysis) were applied to evaluate spatial variations, for the years 2005 to 2020, and Phreeqc software was used to assess the saturation indices determine the dominant geochemical processes source responsible for surface water quality. The dominant minerals of the Tigris River were gypsum, anhydrite, and halite. The Tigris River is within the permissible limits for drinking, except at the Tharthar-Tigris Canal and Diyala River, and the main water quality deterioration factors of the Tigris River were recognized as: total dissolved solids, E. coli bacteria, fecal coliform bacteria, BOD5, and COD. By applying the SPSS program, two factors were identified. The first anthropogenic factor discharged into the river represents 71.27% of the variance and is comprised of agricultural land wastewater and sewage water. While the second factor represents 17.02%, indicated by the variables Ca2+, K+, Mg2+, and SO42−. This factor accounts for the chemical weathering of rocky components. It is recommended that a periodic monitoring system is needed to. follow up on pollution levels and water quality for the Tigris River, by conducting seasonal surveys.

The Tigris River represents one of the main sources of water with the Euphrates River in Iraq. Iraq is plagued by a water shortage as well as water resource management issues and these can be impact on the water quality. For these reason, the study area included the water of the Tigris River to show effect of the shortage of the annual flow on the water quality. The length of the Tigris River in Iraq is 1900 km 2 and includes (534) km 2 into the study area, Six stations along the Tigris River starting from Mosul station (North part) to the Al-Azizziyah station (Middle part) of Iraq. All samples were analyzed for physiochemical parameters such as water temperature, pH, EC, TDS, TH, major ions (Ca 2+ , Mg 2+ , Na + , K + , SO 4 2-, Cl -, CO 3 and HCO 3 ), and nutrients (NO 3 ). Also, using the available historical climate data includes (Rainfall and Temperature) and Annual flow of the Tigris River for the period . Suitability of water for Irrigation uses was evaluated depending on the criteria or standards of acceptable quality for that use. In addition to the statistical correlation coefficient method was applied also. Water of the Tigris River were classified as CaHCO 3 -water type at ST.1 and ST.2, While, from ST.3 to ST.6 classified as NaSO4-water type. Suitability of water for drinking purpose is evaluated depending on the criteria or standards of acceptable quality for that use (WHO and Iraqi Standard). All surface water stations of the Tigris River are unsuitable for drinking and not within the standard quality criteria for most of physiochemical parameters. Additionally, ST.1 and ST.2 fell within Excellent class, while, from ST.3 to ST.6 fell within the Permissible class based on the suggested limits of EC value (Ayers and Westcot, 1985) for irrigation. According to the Don (1995) classification of the irrigation water depend on sodium hazard based on SAR values, ST.1 and ST.2 stations of the Tigris River were classified as Good class but from ST.3 to ST.6 which classified as Doubtful class.

Aims of this Study: To investigate the climate change{effects in Iraq on the quality and quantity of the water of the Tigris River from {Mosul” city to South of Baghdad city.00 This paper provides a review of the observed and the predicted impacts of climate change on the water quality in the Tigris River in Iraq. Study Design: Cross-Sectional study. Place and Duration of Study: The study area is starting {from Mosul city which is located in {the north part of Iraq to the Al-Azziziyah city located in the south of Baghdad (2005-2012) . Methodology: The current study was include the available historical data which are the discharge and hydrochemical analysis includes (Ca, Mg, Na, K, Cl, SO4, HCO3, TDS,NO3, and EC) were taken from 6 stations along the Tigris’ River from Mosul to the south of Baghdad’ cities for the years 2005 to 20112. The available historical climate data’ includes (Rainfall and Temperature) for the period 1990-2012. In this paper also, used some of pervious studies and compared them with the current results. Results: The average annual flow of the Tigris River in Mosul station for the period (1990-2012) ranged between’ (193.8-906) m3/sec and for Sammarra station ranged between’ (366-977) m3/sec. Then, between south of Sammarra’city and north of Baghdad city, Canal of Dijla’joins the Tigris River has a discharge ranges between’ (9-217) m3/sec. After that, the ’Tigris River inter to Baghdad city, the discharge value range between’ (392-1173) m3/sec’and continue his flow to the south of Baghdad city and Diyala River joins it with discharge’range between (55-193) m3/sec. Finally, the Tigris River reaches to’Al-Azizziyah city station with’discharge ranges between (134-769) m3/sec. Conclusion: In general the water quality of the Tigris River are sulfates, calcium, and magnesium. But in Canal of Dijla the most dominant ion is sodium due to agricultural activities and geology of the area consist of gypsum rocks and this can be effects on water quality of Tigris River in the next station (Baghdad). In Al-Azizziyah city the sulfates, calcium, and Sodium is high level due to drainage from irrigation, industrial“and domestic activities.

The study aims to examine the impacts of future climate change on the rainfall quantiles for the main sites of the Tigris River basin, including Mosul, Tikrit, Sammara, and Baghdad. There are two approaches, first: the global climate models ( GCMs): (CMCC-CM2-SR5, CNRM/ESM2-1, EC-Earth3/Veg, MPI-ESM1/2-LR, MRI-ESM2/0, and NorESM2/MM) have been developed to show the future climate change depending on the precipitation data. They were designed along three periods, the reference period (1995-2015), the near-term (2020-2040), and the mid-term (2041-2060). Second, the prediction of the expected Rainfall-Depth (Q) for a return period (2-100 years) based on the rainfall data for 2000-2021 by applying the probability distribution function using the HEC-SSP software. Then, determined the expected Runoff-Depth depending on the results of the predicted probability of Rainfall-Depth for a specific return period and applied the Soil Conservation Service-Curve Number (SCS-CN) model to estimate the CN values of the catchment area from the soil classification according to maps of Land use/cover (LULC) and hydrologic soil grouping (HSGs) generated by the ArcGIS software from the FAO Soils Portal website using Harmonized World Soil Database (HWSD) and the HEC-HMS. The HEC-RAS program is used to create flood maps by simulating runoff depth for forecasting 100 years. The results of the (GCMs) models found the ensemble precipitation change tends to increase at Mosul and Tikrit sites, while Sammara and Baghdad sites noticed no significant changes for both the near and midterm. The flood map reveals that the expected runoff has covered the urban areas.