Ecological and Economic Impacts of Land Use and Climate Change on Coastal Food Webs and Fisheries project SWAT-MODFLOW model of the Suwannee River

This resource contains the SWAT-MODFLOW model for the Suwannee River in the Southeastern United States, which was used in the Ecological and Economic Impacts of Land Use and Climate Change on Coastal Food Webs and Fisheries project. This project was funded by the National Academies of Sciences Engineering and Medicine Gulf Research Program (Grant No. 200011709) to evaluate how basin-wide changes in land/water use and a changing climate will influence the quality of natural resources in the Suwannee River estuary, which supports several imperiled species, multimillion-dollar fisheries, aquaculture, and a tourism economy (https://waterinstitute.ufl.edu/research/featured-projects/ecological-and-economic-impacts-of-land-use-and-climate-change-on-coastal-food-webs-and-fisheries/). The modeling framework implemented in this resource, SWAT-MODFLOW, couples the Soil and Water Assessment Tool (SWAT) to the U.S. Geological Survey modular finite-difference flow model (MODFLOW) to produce an integrated surface-groundwater model (https://swat.tamu.edu/software/swat-modflow/). Within SWAT-MODFLOW, SWAT handles most surface and soil processes, MODFLOW handles groundwater processes, and both models interact to simulate stream flows.

The SWAT portion of this model was developed using USGS digital elevation models (30 m resolution), land cover from USDA CropScape Data Layer 2020, Florida Department of Health and Georgia Department of Health septic tank data, STATSGO soil maps from the Natural Resources Conservation Service (NRCS), the National Hydraulic Data set, spring location data from the Florida Department of Environmental Protection (FDEP), rapid infiltration basins and spray field location data from FDEP, waste water discharge data from the National Pollutant Discharge Elimination Systems (NPDES) and the Permit Compliance System (PCS), and North American Land Data Assimilation System (NLDAS) weather data. Agricultural and silvicultural production land uses and management practices were co-developed with stakeholders in a participatory modeling process (PMP) within the associated Floridan Aquifer Collaborative Engagement for Sustainability (FACETS) project (https://floridanwater.research.ufl.edu/). A subset of these co-developed land uses and management practices was selected and implemented within SWAT for the Suwannee River Basin SWAT-MODFLOW model, following consultation with stakeholders in the project's Community Advisory Committee and Scientific Advisory Committee. These land uses included row crops (corn-peanut, corn-carrot-peanut, cotton-cotton-peanut, and corn-cotton-peanut rotations) forage crops (bermudagrass hay and pasture), and production forestry (slash pine). Additional land uses implemented in SWAT included urban, low-density residential, septic tanks, rapid infiltration basins, fertilized lawns, natural grass, wetlands, and open water. The MODFLOW portion of the model was developed from the North Florida Southeast Georgia (NFSEG) MODFLOW model (version 1.0) as developed by the St John’s River and Suwannee River Water Management Districts. A detailed description of the complete model development process can be found in a document within this resource.

Calibration of the model was conducted using a Bayesian Sample-Importance-Resample method. Data used in the model calibration included: 1) USGS discharge data (Stations 2316000, 2318000, 23177483, 2319000, 2317620, 2314500, 2319500, 2319394, 2315550, 2320500, 2322800, 2322500, 2320700, 2323000, and 2323500); 2) USGS operational Simplified Surface Energy Balance (SSEBop) actual evapotranspiration; and 3) Upper Floridan Aquifer potentiometric surfaces from FDEP. The calibration period of the model was 2010-2021 and the validation period was 1997-2009.