Events & Media

The Bren School of Environmental Science & Management
at the University of California, Santa Barbara

Presents

A PhD DISSERTATION DEFENSE

"Flooding and carbon dynamics on the lower Amazon floodplain"

Conrado Rudorff
PhD Candidate
Bren School of Environmental Science & Management

Friday, June 28, 2013
11:30 a.m.
Bren Hall 1510

John Melack, faculty advisor

Abstract
The Amazon basin stores and cycles large quantities of water and carbon, and floodplains are an important part of these processes. To investigate interactions of hydrological and biogeochemical processes, I combined models of inundation and hydrology with analyses of field data for a large floodplain unit in the eastern Amazon, the Curuai floodplain, over a period of 15 years (1995-2010). I combined digital topography derived from the Shuttle Radar Topography Mission with extensive echo-sounding data to generate a hydraulically correct digital elevation model. Floodplain inundation was simulated using LISFLOOD-FP, which combines one-dimensional river routing with two-dimensional overland flow, and a local hydrological model. An accurate filling and drainage of the floodplain was achieved with quantification of changes in water elevation, flooding extent, and river-floodplain flows. Overbank and channel topography were the main controls of river-floodplain exchanges during high and low-water, respectively. The average annual inflow from the Amazon River corresponded to 82% of inputs from all sources, with dominant sources of inflow varying seasonally among direct rain and local runoff (November), Amazon River (December through August) and seepage (September and October). A water balance analysis and concentrations and transformations of carbon from other studies on the central Amazon floodplain were used to compute the fluxes through the major pathways of carbon loss from the Curuai floodplain. Carbon dioxide outgassing represented 80% of the total carbon loss and its seasonal and spatial variability was further investigated. The seasonal changes in lake mixing patterns exerted an important control over both CO2 production and gas transfer velocities. The range of spatial variation in CO2 concentration was least at low water and largest at high water. Gas transfer coefficients that take into account both wind and heating and cooling at the lake's surface were approximately four times higher than values previously used in regional estimates of gas evasion from lakes on the Amazon floodplain.