Modelling techniques for assessment of Managed Aquifer Recharge combined with water reuse

Future drying conditions coupled with increasing water demand are intensifying the pressure on groundwater systems. Managed Aquifer Recharge (MAR) techniques in combination with water reuse could be valuable measures for mitigating water scarcity problems and promoting sustainable groundwater management. Various modelling methodologies are available to assess the effectiveness and feasibility of these measures in local to regional contexts, with distributed process-based groundwater simulation models being the most widely used for MAR assessments. However, MAR combined with water reuse lies at the interface between anthropogenic (urban) and natural water systems and must be embedded within a regional strategy on water resources management, focusing on feedbacks and interconnections within the entire system, which are crucial for identifying the propagation of effects and the investigation of trade-offs. Therefore, successful planning and implementation of these techniques in regional contexts require assessment tools that reflect this level of integration between multiple subsystems. Here we present an overview of the methodologies and modeling frameworks available for evaluating MAR combined with water reuse, with a primary focus on water quantity aspects. This includes the classification of the methodologies based on the purpose of application, phase of MAR analysis, and their characterization in terms of spatial and temporal scales and resolution, the types of processes included in the modeling frameworks, and the limitations of applicability of the methodologies, also presenting examples in literature. We further discuss the most effective methods—or combinations of methods—for modeling these interconnected systems.