Groundwater banking is the use of aquifers to store water to balance seasonal or longer-term variations in supply and demand. The large storage capacity provided by aquifers can be a valuable tool for conjunctive use of surface water and groundwater as well as other elements of integrated water resources management. Successful groundwater banking requires favorable hydrogeological conditions to efficiently recharge, store, and abstract large volumes of water. Additionally, groundwater banking is also highly dependent upon water management and operational policies to ensure that stored water is not abstracted by other users and that the water accounting system of the bank remains in balance. Accumulated credits to withdraw water should not exceed the capacity of an aquifer to safely produce the water at the design rate-of-return for the bank. System participants need to have confidence that credits issued for recharge can be safely recovered when needed. Groundwater banking systems can cause significant local adverse impacts to other aquifer users and sensitive environments during recovery periods. Groundwater modeling is required to develop a sustainable management system that accounts for temporal and spatial variations in the impacts of both recharge and abstraction activities.