WISE-Wetland: A spatially-explicit carbon cycling model for wetland watersheds

Wetlands play a critical role in the global carbon cycle, functioning as major carbon sinks while also serving as important sources of greenhouse gas emissions. Yet, in most watershed-scale carbon cycling models, wetlands are either highly simplified or omitted altogether, limiting our ability to represent wetland hydrological connectivity and associated carbon dynamics. To address this gap, we developed WISE-Wetland, a spatially explicit watershed-scale carbon cycling model.

We first proposed an improved discretization framework that explicitly represents wetlands as independent hydrological units within a watershed and constructs a wetland routing network. Using this wetland-unit routing network and delineated wetland catchments, we quantified and analyzed key wetland attributes, including area, hydrological connectivity, and routing characteristics. Building on this framework, we integrated a wetland carbon cycling module into WISE (Watershed-based Integrated Simulator for the Environment) that explicitly accounts for wetland routing processes—water retention, water-level dynamics, and wetland carbon transformation, transport, and emission.

WISE-Wetland has been implemented across diverse catchments. Simulations for the northern Krycklan watershed show that explicitly incorporating wetland routing networks substantially reconfigures organic carbon transport pathways and fluxes, leading to a marked improvement in model performance. We also simulated wetland carbon emissions in the Cottonwood watershed, demonstrating that the model can resolve spatial gradients and heterogeneity in wetland CH₄ fluxes, providing a more robust basis for quantifying wetland methane emissions and characterizing their spatial variability. Because watersheds are fundamental units of water and material redistribution, explicitly simulating wetland carbon cycling at the watershed scale offers critical insights into how future, climate-driven hydrological changes may regulate wetland carbon source–sink dynamics. Overall, WISE-Wetland provides a novel framework for advancing quantitative assessments of wetland contributions to regional and global carbon balances.