Abstract ID: 147

The Influence of Historical and Potential Future Deforestation on the Stream Flow of the Amazon River -- Land Surface Processes and Atmospheric Feedbacks

At the micro scale to meso-scale, deforestation generally results in decreased ET and increased runoff, and discharge. At the large-scale, atmospheric feedbacks may significantly reduce precipitation regionally and, if larger than the local ET changes, may decrease water yield, runoff and discharge. In this study, two sets of simulations are made with an offline land surface model and a fully coupled atmospheric general circulation and land surface model to evaluate the influence of historical and potential future deforestation on local evapotranspiration and the discharge of the Amazon River system in the absence of atmospheric feedbacks and in combination with atmospheric feedbacks. The series of simulations clarify a few important points about the impact of deforestation on Amazon River discharge. 1) In the absence of a continental scale precipitation change large-scale deforestation can have a significant impact on a large river system and appears to have already done so, at least in the Tocantins River. 2) Atmospheric feedbacks brought about by large-scale deforestation may be of the same order of magnitude as the changes to local land surface processes but of opposite sign. 3) Changes in the water balance caused by atmospheric feedbacks are not limited to those basins where deforestation has occurred but are spread unevenly throughout the basin by atmospheric circulation. Therefore, changes to discharge and aquatic environments with future deforestation of the Amazon will likely be a complex function of how much vegetation has been removed from that particular watershed and how much has been removed from the entire Amazon Basin. 4) Because of the different temporal and spatial scales of local deforestation and regional climate change, the response in individual tributaries is likely to change with time.

Session:  Feedbacks to Climate - Land cover, surface hydrology, and atmospheric feedbacks. (B)

Presentation Type:  Oral