ICESat passes over the Amazon Basin study area. (Credit: Image by Amanda Hall)
NASA's laser satellite, ICESat, has been used to make corrections to
water level gauges that are critical in monitoring water flow in the
Amazon, the world's largest river. The new study, conducted by
scientists at the University of Bristol, will improve our understanding
of water flows and floodplain processes.
Previously, gauges used to measure changes in water level in the
Amazon were not on the same reference level. This meant water levels
could not be directly compared, limiting the use of the gauges in
research, especially understanding and modelling water flows and
flooding.
Amanda Hall, a PhD student in Geographical Sciences at the University
of Bristol and lead author of the study, said: "When we first
calculated the river slope, the water seemed to be flowing uphill. So we
used data from ICESat to calibrate the Amazon gauges to the same level,
allowing us to make direct comparisons between the gauges and get
accurate readings of actual water levels."
The research, published June 11 in the American Geophysical Union's journal Water Resources Research,
is the first study to use ICESat elevation data to make the necessary
adjustments to the water levels at each gauging station, to ensure they
are all on the same initial level.
The technique was carried out for six Amazon gauges upstream of
Manaus, Brazil where the river is known as the Solimões. The corrections
to the gauges were large and ranged from -7.82m to 13.37m.
Accurately estimating water levels and river slope in the Amazon is
essential for understanding the exchange of water with the floodplain
and other processes, such as the transport of sediments and the release
of greenhouse gasses from Amazon wetlands into the atmosphere.
The method developed by the Bristol scientists can be applied to
other unlevelled gauges in areas where ICESat data are available.
"ICESat elevations can also be used to find water levels in places
where there are no gauges at all," said Amanda Hall. "This is
significant in terms of modelling remote river basins, where gauges
don't exist or are difficult to access. We can now get accurate water
levels for model comparison where there were none before."
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