Extracting water elevation profile extraction for narrow rivers from the SWOT Pixel Cloud

The SWOT satellite, launched 2022, carries the KaRIn swath altimeter that provides two-dimensional maps of water surface elevation (WSE), using interferometric processing of bistatic SAR images pairs. The first level of available WSE product is the pixel cloud, which contains one geolocated point with the derived WSE for each water pixel in the SAR images.

Derived products are also generated and distributed for every for each of the river and lakes in the corresponding prior database.

The high signal level on water surfaces in the SWOT images allows the WSE to be retrieved in smaller water structures, such as rivers or canals less than 50m wide. Although the standard lake and river products are not available for these small structures, valuable information can still be extracted from the pixel cloud.

Extending the preliminary work presented in [Zawadzki et al, 2024], we have developed open-source tools to retrieve the WSE profile along linear features for which exogenous information is available. For example, the linear feature corresponding to a small river in the OpenStreetMap database can be used to extract the time series of its WSE profile. Further hydrologically relevant information can then be derived from the profile and its temporal evolution.

We will present results to illustrate the possibilities and limitations of the proposed method, as well as recommendations for improving the water surface elevation profile estimation for small hydrological targets in difficult environments.

 

 Zawadzki, L., Gasnier, N., Fjortoft, R., Pena Luque, S., Desroches, D., Picot, N., and Barroso, T.: On the potential of monitoring small water structures with SWOT, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17205, https://doi.org/10.5194/egusphere-egu24-17205, 2024.

https://github.com/SWOT-community/PixCDust

SWOT data are available on both hydroweb.next and PO.DAAC portals.