The Surface Water and Ocean Topography (SWOT) Mission River Database (SWORD): A Global River Network for Satellite Data Products

Abstract

The upcoming Surface Water and Ocean Topography (SWOT) satellite mission, planned to launch in 2022, is the first mission to focus on measuring hydrological processes in Earth's surface water. As such, SWOT will vastly expand observations of global rivers ≥100 m wide. SWOT will provide a variety of data products, including a global vector river product containing water surface elevation (WSE), width, slope, and estimated discharge. Practical application and consistency of the SWOT vector products requires a prior global river network database divided into reaches. Here, we introduce the SWOT River Database (SWORD). SWORD will serve as the framework for the SWOT river vector products consisting of river reaches (∼10 km long) and nodes (∼200 m spacing). We generate SWORD by combining several global river‐ and satellite‐related data sets into one congruent product. When defining river reaches, we incorporate natural and human‐created river obstructions, basin boundaries, tributary junctions, and SWOT orbit track information. SWORD contains a total of 213,485 reaches and 10.7 million nodes. Globally, 77.3% of river reach lengths are between 10 and 20 km with a median reach length of 10.5 km. 95% of river reaches ≥10 km will have sufficient SWOT observations to provide discharge estimates at least once per orbit cycle. SWORD also contains many useful hydrologic and morphological attributes and is designed to be expandable in the future. Even before the launch of SWOT, it can serve as a framework for global hydrologic analyses using models, in situ measurements, and additional satellite observations.