Development and application of SWAT-MODFLOW in surface water-groundwater interactions: Current status and future challenges

Hydrological systems are highly complex, with surface water and groundwater components intricately linked rather than operating in isolation. Their interactions play a vital role in determining a region’s overall water balance, a realization that has driven the development of integrated models to overcome the limitations of standalone tools. Traditionally, standalone SWAT has been a staple for simulating land-surface hydrological processes, including precipitation-runoff transformation, soil erosion, and nutrient transport, excelling at capturing land use, soil, and climate impacts on surface water fluxes at large spatial scales. MODFLOW, meanwhile, remains the preferred model for detailed groundwater flow simulations, accounting for aquifer properties, recharge, and pumping. However, neither can fully capture the bidirectional feedback between surface and subsurface water systems, highlighting the necessity of the coupled SWAT-MODFLOW model. This article reviews key advances in SWAT-MODFLOW coupling strategies, systematically evaluates the performance of the coupled model versus standalone SWAT and MODFLOW across different hydrological scenarios, identifies research priorities, pinpoints key uncertainties, and explores potential future research directions. The coupled model enhances integrated water resource simulations by comprehensively capturing SGI feedback mechanisms, albeit at the cost of increased complexity, while standalone models retain advantages in their respective specialized domains. Beyond synthesizing existing knowledge, this review advances the field by forming a more comprehensive and refined understanding of SWAT-MODFLOW’s application status, particularly clarifying progress in emerging fields such as extreme climate adaptation and micro-pollutant control over the past five years. It also addresses gaps in core analysis dimensions of prior reviews by systematically analyzing multi-solute migration mechanisms in SGI systems, constructing a multi-source uncertainty (parameter-structure-data) quantification framework, and elucidating uncertainty transfer laws of coupled models at the regional scale. As an integrated hydrological model, SWAT-MODFLOW improves the understanding of SGIs and supports the identification of water management solutions across diverse research projects. SGI modeling remains an ongoing process fraught with uncertainties and unresolved questions, requiring continuous reassessment and adaptation to emerging data. The modeling approaches outlined herein can be applied to simulate novel SGI scenarios involving various anthropogenic and natural impacts, enabling scientists to monitor water resources more accurately and supporting policymakers in making informed decisions to ensure equitable water availability. Finally, integrating the latest research trends, this review proposes a future research direction centered on “water quantity-water quality-ecology-carbon neutrality” collaboration. This breaks through the limitation of existing reviews that focus on optimizing single hydrological processes, providing more targeted theoretical guidance and technical references for the practical application of coupled models in addressing complex resource and environmental problems. Looking ahead, the validated SWAT-MODFLOW model will serve as an effective tool for guiding water resource management strategies in the coming decades, given its accuracy in simulating groundwater levels and streamflow.