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

Abstract

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 (m3/sec) with total dissolved solids (mg/l) and main cations (Na+, Ca2+, Mg2+, and K+) and anions (Cl‾, SO42, 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 m3/sec respectively. While for Ali Al Gharbi and Amara sites are with an average of 183.99 and 68.7 m3/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.