Over the past decades in the country, extraction of groundwater resources, especially for agricultural use, has caused irreversible damage to aquifers, and a sharp decline in water levels and the loss of financial resources due to the need for wells, ground leveling (dismantling of facilities Infrastructure, buildings, etc.). In order to prevent the continuation of the current decline, management and groundwater protection should be considered as a basis for the planning of the country. In this regard, the use of numerical models in the form of knowledge and on condition of the availability of the field can be provided as an efficient tool for relevant managers in order to facilitate planning and decision making. Such models would well illustrate the underlying groundwater system under study, which would allow the system to respond to various human stresses such as irrigation, pumping, construction of water structures, and the like. In this regard, in this thesis as a case study, the Lenjanat Plain Aquifer has been studied using rainfall data, hydrologic data, exploratory wells, geology, piezometers and available statistics from water resources harvesting in recent years. And the layout of this plain has been slightly expanded by the GMS software and Modflow numerical code. The Lenjanat sub-basin is located in the western part of the Gavkhoni basin, due to the interconnectedness between the river and the aquifer and the vast amount of land allocated to it, as well as the location of large industries such as Mobarakeh Steel and Isfahan Steel, the existence of urban and rural drinking, and The area of the agricultural sector is one of the most important sub-basins in the region. In the aquifer modeling process in a period of 6 years, using a conceptual model in the fall of 2007, the modeling was carried out in a steady state, Then, in 3 years, from the beginning of the water Year 2007-2008 to the end of the water Year, 2009-2010, the modeling was carried out in a non-standard state, and then the made model was calibrated. After that, the model has been verified for the next three years (water Years 2010-2011 to the water Year 2012-2013). The reason for choosing these years for modeling, the availability of the data needed during these years and the inclusion of the three wet, dry and normal weather regimes in the years of modeling and validation years for the study area It is desirable. The reason for choosing these years for modeling, the availability of the data needed during these years and the inclusion of the three wet, dry and normal weather regimes in the years of modeling and validation years for the study area It is desirable. During the modeling, the mean absolute error (MAE) was constant in the steady state and during verification was 0.62, 1.32 and 1.68 meters respectively, which is close to the computational values of the simulated model with observation values this year Shows. Finally, after completing the modeling, with the definition of different regeneration and improvement scenarios, aquifer behavior was studied and assessed for the near future with consideration of future climate conditions from autumn 2018 to the horizon of 2021. The results of the implementation of these scenarios showed that if groundwater withdrawals were carried out in accordance with the current trend, groundwater level dropped by 2.15 meters over three years and the water level dropped over 13 years from the beginning of the modeling in the fall of 2007 to the end of the summer of 2021, it was 8.71 meters. In this way, the water resources of the region are facing a serious crisis with the continuation of the current situation. Considering the predominant use of groundwater resources in the agricultural sector, it is necessary to apply scenarios to reduce the use of water resources in the agricultural sector to improve the situation. The planned scenarios include a 10% and 20% decrease in crop area, a change in crop pattern, a change in irrigation pattern, and eventually the combination of these scenarios together. The results of these scenarios showed that changing the pattern of irrigation with a 20% reduction in the level of the cave had the best result, according to which the condition of the aquifer was reached and the water level during the three years of forecasting was 5 centimeters It's high. Keywords : Lenjanat aquifer, quantitative model, Modflow code, GMS software