Impact of Aquatic and Emergent Riparian Vegetation on Lake Water Volume Retrieval from the SWOT Mission

Abstract:

The future SWOT mission will help fill observation gaps of inland water storage and flux. It will allows it to retrieve the water level of lakes with an area above 250 m x 250 m and rivers larger than 100 m at a 10 cm vertical accuracy after averaging over 1km2. However, few studies have examined the impact of aquatic and emergent riparian vegetation on SWOT’s signal. The following two issues have therefore been investigated: (1) the aquatic vegetation (i.e. algae) and emergent riparian vegetation might influence the water level accuracy by affecting the backscattering coefficient values of SWOT; (2) total water volume change may be underestimated due to water extent affected by aquatic and emergent riparian vegetation. AirSWOT is an airborne mission also carrying a SWOT-like sensor, but at different incidence angles. Still, it can help assessing the influence of vegetation on the Ka-band signal. AirSWOT flew over Mamawi Lake in the Peace-Athabasca Delta, Canada, during summer 2017 giving an insight on vegetation impact on such interferometer data for one of the world’s biggest inland delta. To establish the land cover classification, areas of aquatic vegetation and open water were located using a water mask from AirSWOT’s color-infrared camera, while areas of emergent riparian vegetation are located using RADARSAT 2 double-bounce backscattering. SWOT-like observation were then simulated using a SWOT simulator developed by NASA’s Jet Propulsion Laboratory with land cover classification extent and backscattering coefficient values from AirSWOT. Four scenarios with different land cover types comprising land, open water, aquatic vegetation and emergent riparian vegetation were simulated. Preliminary results indicate that water level estimates in the presence of aquatic vegetation are similar to those for open water. Investigation over emergent riparian vegetation and water volume estimates are ongoing.