Widespread and Exceptional Reduction in River Water Levels Across the
Amazon Basin during the 2023 Extreme Drought Revealed by Satellite
Altimetry and SWOT
Abstract
In late 2023, the Amazon River Basin experienced its most extreme
drought, putting its population and ecosystem at major risks. Gauges
that were still functioning measured the lowest river water levels (RWL)
on record. Here, satellite observations, including Surface Water Ocean
Topography (SWOT), reveal the spread and timing of extremely low RWL
across the entire river system. Nadir altimeter observations show that
the 2023 minimum RWL in Central Amazon were more than 3 m below their
annual average, representing two to three times its mean variability.
Additionally, SWOT enables the first basin-scale characterization of the
reduction in RWL with a spatial resolution of 200 m and how it
propagates with time. Large-scale evaluation with gauges suggest that
SWOT outperforms classical altimetry in estimating RWL, even if observed
biases need further investigations. SWOT offers a new opportunity to
understand hydroclimatic extremes and their broad impacts on the
environment of the Amazon.