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Wednesday, April 11 • 2:30pm - 2:45pm
SYMPOSIA-17: Results from a New USGS Simulation Model of Shallow Groundwater Across the Contiguous United States (CONUS)

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AUTHORS: Ward Sanford*, Wes Zell, Meredith Reitz – U.S. Geological Survey

ABSTRACT: The U.S. Geological Survey (USGS) has been collecting and publishing data on the nation’s water resources for well over a century. Recently the USGS has teamed up with the U.S. Environmental Protection Agency (USEPA) to create a shallow groundwater model of the CONUS that is producing national-scale maps of water-table depth, vadose zone conditions, and stream base flow at a 250-m resolution. The groundwater-flow system, driven by a recent USGS estimate of the magnitude and distribution of groundwater recharge across the CONUS, was simulated using the USGS code MODFLOW. It currently uses a single model layer and simulates an average depth to the water table and base flow to streams. The model has been calibrated to several thousand water levels in wells and to base-flow estimates at several hundred stream gages. Other USGS nation-wide data sets used to create the model include the Digital Elevation Model (DEM), the NHD+ stream network, the National Wetlands Inventory, and a recent map of the surficial geology. A number of hydrologic variables and parameters have been calculated using the model, and are being made available for visualizing at, and downloading from, the USEPA EnviroAtlas. These include long-term averages of recharge, transmissivity, specific yield, soil-water content, water-table depth, residence time of water in the vadose zone, and base flow to streams and rivers. The data is being made available at the 250-m raster format or compiled and averaged at the HUC-12 watershed scale. An estimate of the groundwater age distribution of base flow in streams is also being currently mapped at the HUC-12 scale.

Wednesday April 11, 2018 2:30pm - 2:45pm CDT
LaSalle 5 (7th Floor)

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