Modelling of Groundwater Quality of Tigris River Reach-in Baghdad-Iraq Using Groundwater Modeling System Software

Abstract

The effect of the industrial effluents which discharge to the Tigris River reach in Baghdad city-Iraq, from the industrial and sewage sources on the quality of groundwater was studied for the right and left sides of the flood plain of the river. There are eight sources of pollution along the Tigris River reach in which the effluent discharges were treated partially. In this study, groundwater modelling system (GMS) software (MODFLOW and MT3DMS models) was used to simulate groundwater flow and solute transport. The study area was divided into 5776 cells with a grid size of 250m × 250m with three soils. Sixteen observation wells for the water level and TDS concentrations of the groundwater were used, obtained from the Ministry of Water Resources –Iraq. The MODFLOW and MT3DMS models were calibrated and validated. The validation model was used for the simulation of the groundwater quality for the next 24 years and for three scenarios: (i) concentration of contaminants remain the same, (ii) use of full treatment for accessing the value of TDS concentration to zero, (iii) increase the effluent discharge to the double. The simulation results show an increase in the TDS concentration for all three scenarios during the next 24 years. There are no significant differences in TDS concentration during the next 24 years for the second scenario (full treatment of effluent flow). The difference in TDS concentration was about 3%. TDS concentration change is from the recharge, advection, and dispersion and diffusion process of the groundwater contaminants. When the TDS concentration of the point sources of pollution will increase to double, there is a significant difference in the TDS concentration during the next 24 years which its value was about 13% (1138-1280 ppm). There is no improvement in groundwater quality, but in all three scenarios, the quality will not meet the Iraqi standard limitation of using the groundwater during the next 24 years. The areas of the Tigris River’s left side were affected by the industrial wastewater more than the right side of the river.