The SWOT Mission and Its Capabilities for Land Hydrology

Abstract

Surface water storage and fluxes in rivers, lakes, reservoirs and wetlands are currently poorly observed at the global scale, even though they represent major components of the water cycle and deeply impact human societies. In situ networks are heterogeneously distributed in space, and many river basins and most lakesespecially in the developing world and in sparsely populated regionsremain unmonitored. Satellite remote sensing has provided useful complementary observations, but no past or current satellite mission has yet been specifically designed to observe, at the global scale, surface water storage change and fluxes. This is the purpose of the planned Surface Water and Ocean Topography (SWOT) satellite mission. SWOT is a collaboration among the (U.S.) National Aeronautics and Space Administration (NASA), Centre National d"Études Spatiales (CNES, the French Spatial Agency), the Canadian Space Agency (CSA), and the United-Kingdom Space Agency (UKSA), with launch planned in late 2020. SWOT is both a continental hydrology and oceanography mission. However, only the hydrology capabilities of SWOT are discussed here.After a description of the SWOT mission requirements and measurement capabilities, we review the SWOT-related studies concerning land hydrology published to date. Beginning in 2007, studies demonstrated the benefits of SWOT data for river hydrology, both through discharge estimation directly from SWOT measurements and through assimilation of SWOT data into hydrodynamic and hydrology models. A smaller number of studies have also addressed methods for computation of lake and reservoir storage change or have quantified improvements expected from SWOT compared to current knowledge of lake water storage variability. We also briefly review other land hydrology capabilities of SWOT, including those related to transboundary river basins, human water withdrawals, and wetland environments. Finally, we discuss additional studies needed before and after the launch of the mission, along with perspectives on a potential successor to SWOT.

CryoSat-2 Altimetry Applications over Rivers and Lakes

“…Some of the strategies developed for CryoSat-2, such as new approaches to densification of altimetry measurements and combination with hydrodynamic models will support processing and application of data from the upcoming SWOT mission. SWOT, expected to be launched in 2020 by NASA, will be the first satellite altimetry mission to provide images of water heights (instead of points at nadir) [80]. Hence, its capabilities and potential applications over inland water bodies have been assessed in many studies [64,[81][82][83][84].…”

Fifteen Years (1993–2007) of Surface Freshwater Storage Variability in the Ganges-Brahmaputra River Basin Using Multi-Satellite Observations

“…There is also ongoing work to extend the GIEMS time series from 2007 to present. A consistent global SWS dataset from 1993 to present will play a key role in the definition and development of the future hydrology-oriented satellite missions such as the NASA-CNES SWOT (Surface Water and Ocean Topography) dedicated to surface hydrology [68,69].…”

Dynamic River Masks from Multi-Temporal Satellite Imagery: An Automatic Algorithm Using Graph Cuts Optimization

“…The availability of accurate river masks can improve the performance of spaceborne water level measurements-especially in narrow rivers. Moreover, the method proposed in this study can help to address the science requirements of the Surface Water and Ocean Topography (SWOT) mission, which will be launched in 2020 [76].…”