Terrestrial Water Cycle Seminar

NASA-Hydrological Sciences Branch

The wetlands of low-land rivers and lakes are massive in size and in volumetric fluxes, which greatly limits a thorough understanding of their flow dynamics. Wetlands, lakes, and rivers cover five to eight million square kilometers globally, blanketing up to six percent of the earth’s land surface. An understanding of the flooding dynamics and hydrologic exchange between rivers and related floodplains relies on measurements of water levels recorded at gauging stations along a main channel. Given the vast size and remote location of large tropical basins such as the Amazon and Congo, satellite observations remain a viable approach to constraining and validating basin scale hydrologic models.

In this presentation, I will present wetland studies using remote sensing and modeling in the Amazon, Congo, Logone, Atchafalaya wetlands. First, interferometric processing of JERS-1 SAR data from the central portions of both the Amazon and Congo Basins provides centimeter-scale measurements of water level change. Despite being large, low-relief, tropical river systems, the floodplains and wetlands of the Amazon and Congo Basins show markedly different surface water flow hydraulics. Second, flood inundation maps in Logone floodplain, Lake Chad Basin are generated from 33 multi-temporal Landsat Enhanced Thematic Mapper Plus (ETM+) images. Coefficients of determination between flooding extents and water height variations are greater than 0.91 with 4 to 36 days in phase lag. Third, the spatial and temporal distributions of water level are quantified in the Atchafalaya wetland using spaceborne data and the LISFLOOD-FP hydrodynamic model. This model provides 1-D diffusive channel flow and 2-D dynamic floodplain flow. The model shows water level changes in the floodplain and these results can be validated by PALSAR repeat pass interferometry.