wcm.03.2025.583.594

A steady-state groundwater flow model was proposed to examine how rising water demand in Erbil City affects the groundwater level in Northern Iraq. In GMS 10.8.6, the model was developed and it was calibrated to 2007 data of groundwater levels for 13 wells by going through a trial-and-error optimization process. GMS used the Newton Solver package (NWT) to strengthen the accuracy and consistency of its groundwater flow calculations. Model quality was evaluated using statistical indicators (ME, MAE, RMSE, and NSE). The calibration performance reached 0.962 in 2007, while for the years 2010, 2013, 2016, 2019, 2022, and 2024 the values ranged between 0.809 and 0.966 during validation. The forecasts for the future were done for the years 2027, 2029, 2031, 2033 and 2035 by assuming different rates of groundwater abstraction (20% for 2027 and going up to 100% in 2035) and groundwater recharge used the monthly average rainfall values from 1991 to 2022. Groundwater dropped citywide as demand for water increased. Groundwater head trends, estimated using Mann-Kendall and Sen’s slope, found every observation well displayed extreme downward trends (p = 0.027), suggesting a steady decrease in all the areas. The values of R² between what the model predicts and what happens in reality were from 0.827 to 0.972, showing that the model works very well. In ArcMap 10.8, the spatial interpolation shown consistent descent of groundwater levels across several urban areas. It is necessary to create planning for water resources now and in the future and to target interventions where big drops are noticed. With the model, we can estimate how groundwater responds to future urban water demand