Abstract's details
Use of SWOT for understanding dynamics of Amazonian ria lakes and its interaction with the Amazon River
Event: 2025 SWOT Science Team Meeting
Session: Hydrology: SWOT Lakes, Estuaries and Wetlands (SLEW)
Presentation type: Poster
Ria lakes are widespread in the Amazon River basin, where they comprise a crucial component of the Amazon ecosystem. These lakes, formed as flooded river valleys due to post-glacial sea level rise, remain poorly understand in terms of their hydrodynamic interactions with the Amazon River. Yet, understanding such lake-river interactions is essential for assessing functional connectivity and seasonal dynamics in water and sediment fluxes across the Amazon freshwater system. With the Amazon River experiencing its most severe drought in two consecutive years in 2023-2024, further stresses on lake-river connectivity are expected, which is further compounded by dam construction and deforestation under a changing climate in the region. To investigate this connectivity, we integrate multiple SWOT data products, including LakeSP, RiverSP and PIXC, along with optical images collected from Sentinel-2, PlanetScope, and Landsat-9, to evaluate the relationship between each ria lake and the adjacent Amazon River. By examining the seasonal dynamics of the lake-river relationship since July 2023, we aim to obtain a detailed understanding of the role of the Amazon River in controlling the behavior of ria lakes.
To date, we have analyzed 21 ria lakes along the Amazon River mainstem, which exhibit an average annual water surface elevation (WSE) amplitude of 10 meters. The WSE hydrographs of these ria lakes show a temporal lag from upstream to downstream along the Amazon mainstem, confirming the central control of the Amazon River. Among the 21 ria lakes, 20 display a strong 1:1 relationship between lake and adjacent river WSE, either consistently throughout the observed period or until the water level falls below a threshold “sill” level. This “sill effect” is observed in 19 of the lakes, and is likely driven by: (1) a functional disconnection of the lake with the Amazon River below this sill (hydrogeomorphic control), or (2) a shift in dominant influence from the downstream river to the upstream lake catchment (hydrodynamic control). We further test these mechanisms using SWOT-derived longitudinal water surface profiles along the ria lakes and their adjacent Amazon River mainstem, in combination with water surface connectivity interpreted from optical imagery. These findings offer new insights into the intricate controls of the ria lake system, and lay the foundation for advancing our understanding of sediment dynamics and refining the typology of the Amazonian lakes.
Back to the list of abstractTo date, we have analyzed 21 ria lakes along the Amazon River mainstem, which exhibit an average annual water surface elevation (WSE) amplitude of 10 meters. The WSE hydrographs of these ria lakes show a temporal lag from upstream to downstream along the Amazon mainstem, confirming the central control of the Amazon River. Among the 21 ria lakes, 20 display a strong 1:1 relationship between lake and adjacent river WSE, either consistently throughout the observed period or until the water level falls below a threshold “sill” level. This “sill effect” is observed in 19 of the lakes, and is likely driven by: (1) a functional disconnection of the lake with the Amazon River below this sill (hydrogeomorphic control), or (2) a shift in dominant influence from the downstream river to the upstream lake catchment (hydrodynamic control). We further test these mechanisms using SWOT-derived longitudinal water surface profiles along the ria lakes and their adjacent Amazon River mainstem, in combination with water surface connectivity interpreted from optical imagery. These findings offer new insights into the intricate controls of the ria lake system, and lay the foundation for advancing our understanding of sediment dynamics and refining the typology of the Amazonian lakes.