Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

La Niña influences Amazon flooding

05.11.2003


Work recently published in Nature announces a significant correlation between sediment deposition in two Bolivian rivers, which flow into one of the principal tributaries of the Amazon, and climatic events of the ENSO (El Niño Southern Oscillation) type. It is the fruit of a research partnership between the IRD, the Bolivian Meteorology and Hydrology Centre in La Paz and scientists from the universities of Washington and California. The results represent a major advance in the study of the Amazon Basin’s hydrology and geochemistry dynamics since the beginning of the XXth century (the HYBAM programme). They further more particularly knowledge of the impact of climatic variability on the processes controlling the sediment transport and deposition between the Andes and the Atlantic Ocean. They also provide useful clues for predicting strong flooding events in this region.



The Amazon Basin in figures…

- 6 million km_ -representing 5% of the Earth’s exposed land surface,
- 7 countries: Brazil, Peru, Bolivia, Colombia, Ecuador, Venezuela, French Guiana - annual average discharge rate of the Amazon: 209 000 m3/second


- average annual input of 6 600 billion m3 of freshwater and 600 to 800 million tonnes of sediment into the Atlantic (15% of all freshwater input into the oceans)

The HYBAM programme (Hydrology and Geochemistry of the Amazon Basin)

The Amazon Basin is a highly complex system to study. Its expanse is enormous, it includes a great variety of landforms and the different rivers contributing to the system are diverse in size and source. Research requires a substantial array of technical means and human resources. To ensure their availability, the IRD signed in 1994, in the context of a convention it had concluded with the Brazil National Council for Scientific and Technological Development (CNPq), a cooperation agreement with the University of Brasilia and the National Electrical Energy Agency (ANEEL, Agence Nationale d’Énergie Électrique), the initiator of the HYBAM programme. Its main objective: improve on knowledge about the hydrology and geochemistry of the Amazon Basin acquired since the beginning of the XXth century. Other major goals are to assess the input the Amazon feeds into the ocean and to determine the impact of climatic oscillations, such as El Niño, on the dynamics of the basin’s hydrological and sedimentary system.

About 40 researchers and engineers (half of whom are partners from the countries of the South) are currently involved in this multidisciplinary programme: climatologists, hydrologists, geochemists and remote sensing and modelling specialists.

The HYBAM project has accomplished around 30 or so campaigns in the Amazon region. These, combined with monitoring data obtained from the HYBAM reference network of hydrological and geochemical stations deployed in Bolivia since 1983 and in Brazil in 1995, have yielded precise measurements of the water, sediment and geochemical inputs contributed by the Amazon’s main tributaries. This year, 2003, has seen this network, now accorded the official designation of Environment Research Observatory (ERO), set up on these rivers, with joint IRD-INSU-Ministry of Research finance. This HYBAM ORE is based on a permanent network of 4 hydrological stations installed on the Andean piedmont in Bolivia, Peru and Ecuador, 6 on the Brazilian rivers, and 2 on major rivers in French Guiana. The objective of this ORE is to assess the fluxes of water and materials in the Amazon Basin and, importantly, the impact of climatic variability and human activity on such fluxes.

Results already acquired have shown the importance of the system’s flood zones on transport of water, sediments and associated chemical elements. In order to understand processes which might interfere with these flows, the HYBAM project is focussing on wetlands in Brazil, lakes called "varzeas" and in particular on the Curuai varzea near the town of Obidos. Determination of the input/output balance of this varzea has allowed the development of working models of such Amazonian lakes which are connected to the main river rising in the Andes.

In addition, satellite remote-sensing techniques are currently employed extensively by the HYBAM project. They can be used as much for determining water levels by radar altimetry (Topex, Jason), as for measuring the down-gradient of rivers on the plain (DGPS), or defining the surface concentrations of matter in suspension in the flood-lakes and the main river streams (Landsat and ENVISAT).

Amazon flooding and climatic variability One of the HYBAM programme’s main lines of study concerns the physical erosion and chemical leaching processes along with the mechanisms of transport and deposition of matter from the Andes down to the Atlantic Ocean.

The research of Laurence Maurice Bourgoin, geochemist at the IRD, and his American colleagues was conducted on the flood-plain on two Bolivian rivers rising from the Andes, which in turn flow into one of the Amazon’s main tributaries. The northern part of the eastern Bolivian cordillera is at present a zone of heavy rainfall and steep valley slopes. Soil and rock erosion of these drainage basins is therefore intense. The quantification of sediment accumulations followed by dating (from the 210Pb content) of sediment beds were the first stages of the work. Subsequent examination of these data in relation to climatological measurements and the development (by the University of Washington) of a new geochronological model revealed that the deposition rates of major sediment accumulations in the flood-plain were not constant in time but episodic, and in the Andes strongly linked to climatic events such as La Niña, the cold phase of the ENSO cycle.

A major advance for the HYBAM programme By calling into question the 210Pb based geochronological dating models hitherto used, this research represents an important advance for knowledge of the sedimentation processes in the plain and of their frequency. That will open the way, among other things, for work on other climatic indices to determine, by region, the influence of these climatic factors on the hydrology and sedimentology of the Amazon Basin, and for more detailed study of a climatic hiatus that occurred in the deposits in the 1970s, observed in one of the sub-basins.

In terms of flood prediction, attention is drawn to the years for which a La Niña is forecast and more especially to those which are preceded by a strong El Niño event.

Bénédicte Robert | EurekAlert!
Further information:
http://www.paris.ird.fr

More articles from Earth Sciences:

nachricht Climate satellite: Tracking methane with robust laser technology
22.06.2017 | Fraunhofer-Gesellschaft

nachricht How reliable are shells as climate archives?
21.06.2017 | Leibniz-Zentrum für Marine Tropenforschung (ZMT)

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

Im Focus: Optoelectronic Inline Measurement – Accurate to the Nanometer

Germany counts high-precision manufacturing processes among its advantages as a location. It’s not just the aerospace and automotive industries that require almost waste-free, high-precision manufacturing to provide an efficient way of testing the shape and orientation tolerances of products. Since current inline measurement technology not yet provides the required accuracy, the Fraunhofer Institute for Laser Technology ILT is collaborating with four renowned industry partners in the INSPIRE project to develop inline sensors with a new accuracy class. Funded by the German Federal Ministry of Education and Research (BMBF), the project is scheduled to run until the end of 2019.

New Manufacturing Technologies for New Products

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Mathematical confirmation: Rewiring financial networks reduces systemic risk

22.06.2017 | Business and Finance

Spin liquids − back to the roots

22.06.2017 | Physics and Astronomy

Hubble captures massive dead disk galaxy that challenges theories of galaxy evolution

22.06.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>