S. I. GEOLOGY OF AFRICA Numerical modeling technique for groundwater management in Samalut city, Minia Governorate, Egypt Ahmed Abdelhalim 1 & Ahmed Sefelnasr 2 & Esam Ismail 1 Received: 25 September 2018 /Accepted: 11 January 2019 # Saudi Society for Geosciences 2019 Abstract The demand for freshwater supplies is progressively ascending owing to the increase of the population expansion and economic growth. Available water resources have been reduced by pollution and over-pumping. Groundwater modeling is a powerful tool for water resources management, groundwater protection, and remediation. The aim of this study is to develop a numerical groundwater flow model for the Quaternary aquifer in Samalut city, Minia Governorate, Egypt. The model is used to determine the hydrogeological conditions of the aquifer, the flow directions as well as calculating the rates of recharge and discharge between surface water and groundwater in the study area. Furthermore, scenarios were designed in the model to assess the response of the aquifer to increase the groundwater extraction in the future. The model was calibrated by trial and error; simulated results were compared to the observed head and contour maps, which were generally in good agreement. No typical steady-state condition is prevailed in the aquifer and groundwater flow directions are toward northeast direction. The River Nile acts as a drain in the study area, while El-Ibrahimiya Canal and Bahr Yusef act as a source of aquifer recharge. The proposed scenarios showed that surface water plays an important role in recharging the aquifer during increasing groundwater extraction. The results showed that the change in the aquifer storage will be decreased from + 48,125 m 3 /day in the current state (2013) to + 27,134 m 3 /day and - 869 m 3 /day when the groundwater extraction is increased by 25% and 50%, respectively. Keywords Groundwater modeling . Groundwater management . Groundwater budget . MODFLOW Introduction Water is vital to the existence of all living organisms, but this valued resource is increasingly being threatened. Egypt lies mainly within the hyper-arid desert environment, where water resources are critically important. Understanding of water re- sources is fundamental to future developments and planning. Currently, the availability of water of acceptable quality in Egypt is limited and getting even more restricted. The distri- bution of fresh water resources and its availability is becoming scarce day by day, owing to population growth and diverse human activities. Egypt depends on about more than 90% of its water supply on the River Nile. Groundwater in Egypt is a vital water resource as it is used for many purposes including drinking, domestic, industrial, and irrigation. Groundwater modeling is a way to represent a system in another form to investigate the response of the system under certain condi- tions, or to predict the behavior of the system in the future (Thangarajan 2007). Groundwater modeling is a powerful tool for water resources management, groundwater protection, and remediation (Baalousha et al. 2013). Decision makers use models to predict the behavior of a groundwater system prior to implementation of a project or to implement a remediation (Kresic 2006). Much hydrological researches have been car- ried on the study area and its vicinities to evaluate the suitabil- ity of surface water and groundwater for use in different pur- poses on hydrochemical basis such as El Sayed (1987), Tantawy (1992), Gomma (1999), Wahaab and Badawy (2004), El Kashouty et al. (2012), Salem (2015), and Esam et al. (2017). The numerical modeling tasks proposed for this study are the first attempt of groundwater modeling effort in This article is part of the Topical Collection on New Advances and Research results on the Geology of Africa * Ahmed Abdelhalim ahmed.mohamed@mu.edu.eg 1 Geology Department, Faculty of Science, Minia University, Minia, Egypt 2 Geology Department, Faculty of Science, Assuit University, Assuit, Egypt Arabian Journal of Geosciences (2019) 12:124 https://doi.org/10.1007/s12517-019-4230-6