Groundwater is an essential water resource in many areas of Erbil city. A significant development is noticed in Erbil city, leading to groundwater quality and quantity depletion. This study aims to predict the effect of increasing the pumping rate in the study area and simulate the chloride transport from the dump site to the surrounding area after a different period. Groundwater Modeling System (GMS) version (10.6.2) is used to model groundwater flow and contamination transport; the model is run for steady and unsteady conditions. The dump site is considered a contamination source in the study area. The result indicates that GMS is a powerful software for modelling groundwater flow and contamination transport, and it can help predict aquifer properties and future behaviour. The correlation between the observed and calculated head was R2 = 0.9917, the calibrated value of hydraulic conductivity was 1.4 m/d for the first layer, 0.0025 m/d for the second layer, and 1.35 m/d for the third layer, the porosity of calibrate value of the model was 0.23 for the first layer, 0.095 for the second layer and 0.37 for third layer. The increase of pumping wells by 25% in the study area leads to an increase in the drawdown of about 9.24 m as the maximum value after the year and 14.2 m after increasing pumping by 50% after ten years from 2022. The chloride concentration spread to about 1.6 km with about 113.9 m/year after 50 years from 2022.