Visualizing the spatial-temporal characteristics of SWOT derived streamflow

The Surface Water and Ocean Topography (SWOT) mission, which is expected to launch in 2022, will observe surface water extents and elevations for rivers greater than 50-100 m wide, enabling river discharge estimation at unprecedented spatial and temporal scales. It will have a 21-day orbit cycle providing a unique space-time sampling pattern for rivers globally. We have developed an application that uses the SWOT orbit and U.S. Geological Survey (USGS) streamflow observations to generate synthetic discharge time-series. The application displays USGS streamflow gauge locations, SWOT observable river reaches from a recently released apriori database, and the SWOT orbit. It allows the user to generate, plot and save synthetic SWOT streamflow estimates for any gauge displayed on the map, while accounting for the spatial-temporal sampling of SWOT and user specified derived discharge uncertainty parameters. It also analyzes the similarity of the synthetic SWOT and in-situ USGS discharges. The tool generates SWOT data starting from a user specified mission start date. Results are shown using a SWOT start date of 01/04/2014, to generate 6+ years of synthetic SWOT discharges. To generate the synthetic SWOT discharges at each gauge location, USGS discharge measurements corresponding with SWOT overpass dates are obtained, and uncertainty is incorporated based on errors resulting from SWOT observations and associated discharge algorithms. The resulting uncertainty is approximated using a gaussian error distribution with a user specified mean and standard deviation. Results for 2,080 sites throughout CONUS derived using the application are shown comparing the 5, 25, 50, 75, 95 percentiles of synthetic SWOT and in-situ USGS discharges. This tool gives scientists a simple and intuitive web interface for accessing synthetic SWOT streamflow estimates to evaluate its utility used in hydrologic applications such as analyzing storm return periods, discharge frequency distributions, and flood dynamics.