Cumulative impacts of hydroelectric dams in the Amazon: far beyond dam sites

The Amazon basin is a complex, coupled human and natural system. National and international sociopolitical and economic interests drive decisions about development in the Amazon affecting its diverse cultures and ecosystem services. With such a complex, internationally important system, how does anyone get a real feel for the scale and complexity of the largest river basin in the world? Remote sensing and metadata analysis are certainly important tools, but Dr. Latrubesse would say you have to go there and see it!

Edgardo M. Latrubesse, Ph.D., Professor, Department of Geography and the Environment, University of Texas at Austin. Latrubesse is a Senior Researcher in the Amazon Dams Network NSF-funded project.

Last week the Amazon Dams Network and Water Institute graduate students and faculty at the University of Florida (UF) had the opportunity to chat with Dr. Latrubesse and hear a lecture about his experiences as a large river geomorphologist working for more than 20 years in South America. We discussed the role of science in affecting policy – to stir debate, to provide investors and planners a third party look at the system at different scales and with different global perspectives, etc. A main take-home point was that whether your research is related to the social, economic or biophysical effects of development or governance in the Amazon, it is important to explore the nested scales of the system and consider the cumulative effects of numerous drivers of change, such as deforestation, dams, and climate change.

To give us his disciplinary experience, Dr. Latrubesse presented on the sources and sinks (areas of storage or deposition) of sediments in the Amazon and South America for his UF Water Institute Distinguished Scholar Seminar.

Dr. Latrubesse started by explaining that most of the sediment load that makes it into the world’s oceans comes from the Himalayas and SE Asia, but smaller Andean rivers have just as high or higher sediment yields (average amount of sediment that makes it to the river per km2 in a watershed). These high yields, however get trapped in the various sinks in the South American lowlands (see his recorded talk for more details).

Of course, humans continue to have effects on the river flow and sediment discharge. In areas of high deforestation, more sediment is released into the rivers due to increased erosion. At the same time dams hold back much of the sediment that would eventually make it to the main stems of the rivers and be released into the ocean. This then in turn affects the Amazon plume of sediment that is vitally important in this highly productive coastal region and to circulation patterns. Thermal anomalies from this plume have also been shown to affect circulation patterns in the Caribbean, exacerbating the risk of tropical storms. Dr. Latrubesse concluded by suggesting that at the current rate of development, these services are expected to be significantly altered in the next few generations if scientist and governments today don’t start thinking more holistically about atmosphere-land-ocean connectivity. He also, emphasized the importance of maintaining certain, sometimes small, rivers free-flowing to avoid significant changes to the services the Amazon, and other major South American rivers, provide.

The Madeira and Amazon Confluence Figure from Aguas Amazonicas

Dr. Latrubesse’s seminar can be watched here: