**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** WETLANDS PROVIDE A WIDE VARIETY OF ECOSYSTEM SERVICES, SUCH AS WATER QUALITY PURIFICATION, MATERIAL TRANSFORMATION, CARBON SEQUESTRATION, FLOOD CONTROL, WILDLIFE HABITATS, AND BIODIVERSITY. CONSTRUCTED AND RESTORED WETLANDS ARE AMONG THE MOST EFFECTIVE BEST MANAGEMENT PRACTICES (BMPS) (ALSO REFERRED TO AS GREEN INFRASTRUCTURE) FOR TRAPPING NUTRIENTS GENERATED FROM AGRICULTURAL FIELDS. ALTHOUGH THE ECOLOGICAL SERVICES PROVIDED BY WETLANDS ARE WELL STUDIED AT THE LOCAL LEVEL, LITTLE ATTENTION IS GIVEN TO THEIR BENEFITS AT THE WATERSHED SCALE. IN A WATERSHED WITH A CONSIDERABLE NUMBER OF WETLANDS, THEIR CUMULATIVE INFLUENCE CAN STRONGLY AFFECT THE MAGNITUDE, FREQUENCY, AND DURATION OF HYDROLOGIC AND BIOGEOCHEMICAL FLUXES OR TRANSFER OF WATER AND MATERIALS TO DOWNSTREAM AQUATIC SYSTEMS. MANY WATERSHED MODELS EITHER IGNORE WETLANDS AS AN INTEGRAL PART OF A WATERSHED OR HAVE SIMPLISTIC REPRESENTATIONS. TO FILL THIS MAJOR GAP IN MODELING WETLAND DOMINATED WATERSHEDS, WE PROPOSE TO FULLY COUPLE THE WIDELY USED WATERSHED MODELS SOIL AND WATER ASSESSMENT TOOL (SWAT+) WITH A RECENTLY DEVELOPED WETLAND NUTRIENT CYCLING MODEL (WETQUAL) FOR IMPROVED UNDERSTANDING OF NITROGEN, PHOSPHOROUS, AND CARBON CYCLES IN AGRICULTURAL WATERSHEDS WITH SIGNIFICANT WETLAND PRESENCE. BEFORE COUPLING THE TWO MODELS, WE WILL FIRST ADD A CARBON TRANSPORT MODULE IN SWAT+, AND IMPROVE FOREST ECOSYSTEM DYNAMICS AND REPRESENTATIONS OF NON-FLOODPLAIN WETLANDS IN SWAT+. THE COUPLED MODEL (SWAT+WET) WILL BE TESTED IN THE TUCKAHOE CREEK AND UPPER CHOPTANK RIVER WATERSHEDS IN MARYLAND WITH DEPRESSIONAL WETLANDS AND IN THE FISH RIVER AND MAGNOLIA RIVER WATERSHEDS IN COASTAL ALABAMA DOMINATED BY HEADWATER WETLANDS. THE FULLY COUPLED SWAT+WET WILL PROVIDE AN IMPROVED WATERSHED-SCALE HYDROLOGY AND WATER QUALITY MODEL THAT CAN TACKLE ANY NUMBER OF WETLANDS AND MORE EFFICIENTLY AND ACCURATELY SIMULATE THE FATE AND TRANSPORT OF NUTRIENTS AT THE WATERSHED LEVEL. THE PROPOSED RESEARCH WILL PROVIDE TOOLS THAT CAN HELP IMPROVE NUTRIENT MANAGEMENT AND REDUCTION OF NUTRIENT LOADS TO SURFACE OR GROUNDWATERS IN LANDSCAPES WHERE WETLANDS PLAY SIGNIFICANT ROLES.