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Scientists correct Amazon water level gauges from space

ICESat passes over the Amazon Basin study area

ICESat passes over the Amazon Basin study area Amanda Hall

Press release issued: 11 June 2012

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 today 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.”

Further information

Amanda Hall is a PhD student in the Hydrology Group in the University of Bristol’s School of Geographical Sciences, a member of the Cabot Institute, and is funded by the Natural Environment Research Council (NERC).

The six gauges levelled were at Manaus, Manacapuru, Anamã, Arumã, Codajás and Itapéua. The average slope over the study area stretch using the levelled gauges was found to be 2.21 cm/km.

Water Resources Research

Water Resources Research is an interdisciplinary journal that publishes original research in the natural and social sciences of water. This includes the role of water in the physical, chemical, biological, and ecological sciences; public health; and related social and policy sciences. It encompasses methodological development of observational, experimental, theoretical, analytical, numerical, and data driven approaches that advance the science of water and its management. Submissions are evaluated for their novelty, accuracy, significance, and broader implications of the findings.

American Geophysical Union

As the premier scientific association for the Geosciences, AGU's highly respected, peer-reviewed journals attract submissions from leaders across the field. With two journals (Geophysical Research Letters and Journal of Geophysical Research-Atmospheres) ranked among the top ten most-highly cited research publications on climate change over the past decade, AGU's editors apply rigorous standards to ensure highest-quality articles in every issue.

Cabot Institute

The Cabot Institute at the University of Bristol carries out fundamental and responsive research on risks and uncertainties in a changing environment. Its interests include natural hazards, food and energy security, resilience and governance, and human impacts on the environment. Its research fuses rigorous statistical and numerical modelling with a deep understanding of interconnected social, environmental and engineered systems – past, present and future. It seeks to engage wider society – listening to, exploring with, and challenging our stakeholders to develop a shared response to twenty-first century challenges. Find out more from www.bristol.ac.uk/cabot.