Damghan plain is located in Semnan Province in northern Iran and is one of the study areas in the northwest of the Central Desert Basin. In this plain, an alluvial unconfined aquifer with an area of 812.4 km2 is situated, and due to the scarcity of surface water in the region, most of the water demands are met by groundwater resources. The groundwater level experiences an annual decline of more than 60 cm. To investigate the aquifer in this plain and manage groundwater withdrawal, a numerical groundwater model is prepared using GMS software and the MODFLOW model. After preparing the information layers to build a conceptual model in the first step of modeling, this data is entered into the GMS software environment. The numerical model is run in two steady and unsteady states for the water year 2020-2021, and after calibration using both automatic and manual methods with the help of available data from different water years during the calibration period, the validation phase is carried out. Due to the correlation between the observed and calculated groundwater levels in the validation phase, the designed model is capable of forecasting the future status of this aquifer. In the last stage of modeling, scenarios are designed to improve the aquifer's status and compensate for the reservoir deficit (-27.23 million cubic meters), and the results showed that only if withdrawal from the exploitation wells is reduced by more than 40% will we witness groundwater balance in this aquifer reaching equilibrium.