Comparison of CO2 flux in an Amazonian natural lake and hydroelectric reservoir

Abstract: Due to global demand for alternative energy sources, the industry of hydropower is continuing to thrive. Not only are there already thousands of dams worldwide, but many more developments are planned for the future. This has increased attention towards the topic of reservoirs, and more specifically their potential to act as a source of greenhouse gases. Despite tropical locations being known as ‘hydro hot spots’, there is still a surprising scarcity of studies existing in these areas. Furthermore, lakes and reservoirs are often grouped together as a singular entity, with response to phenomena such as seasonal dynamics being believed to be the same. The focus of this thesis was therefore to explore CO2 exchange from water bodies in the Amazon. This involved comparison of flux from a hydroelectric reservoir to that of an adjacent natural lake. Data was compiled from previous studies, with necessary additional information also being sourced. The ‘Thin Boundary Layer’ method was used to calculate and quantify fluxes, before then employing statistical methods to aid further analysis. Results revealed that both sites were CO2 emitters continuously throughout the year. Response to seasonal changes was also observed, linking to the influence of the ‘Amazonian flood pulse’. Although both sites experienced greatest flux during ‘low’ phase, different explanations are offered. The natural lake appeared more dependent on hydrological factors such as riverine inputs, whilst changes seen at the reservoir showed stronger links with morphological variables. Data availability, methodological constraints and neglect of other potentially influential factors are however pointed out. Future works in this field are therefore recommended in order to further expand upon these findings.