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Abstract
Dams and their reservoirs play a central role in freshwater carbon cycling as control points for carbon burial and emissions in inland waters. While dams are intensively managed to provide infrastructure services and mitigate their environmental harms, considering carbon impacts in dam management decisions is currently constrained by limited methods for quantifying and incorporating carbon costs and benefits in decision processes. I addressed three major aims to reduce this constraint: 1) evaluate spatiotemporal variability of emissions from small reservoirs to support accurate emissions estimates from these abundant, yet understudied waterbodies, 2) estimate the impacts of dam removals on carbon emissions and storage, and 3) develop a structured decision tool to facilitate the consideration of carbon impacts with other objectives of dam removal. To address the first aim, I intensively sampled carbon emissions from four small reservoirs in Athens, GA over 24-hr periods in the late summer. I found that common practices for sampling small reservoir carbon emissions which fail to account for spatiotemporal variability and measure ebullition can lead to misestimation of total emissions between -89 to 366%. To address the second aim, I combined literature values, statistical, and mechanistic models to estimate carbon fluxes before, during, and after dam removal to determine its net impact on carbon balance in the reservoir footprint. I found that the removal of two large dams decreased the sink strength of the reservoir footprints, but more work is needed to distinguish changes in flux magnitude from changes in flux timing or location due to dam removal. By conducting a systematic review of existing dam removal decision-support tools for aim three, I found that these tools frequently omit common objectives of dam removal. To facilitate structured decision-making inclusive of diverse objectives, I designed a web application to guide users to relevant objectives, metrics, methods, data, and tools for their removal decisions. Dams sit at the intersection of the interacting crises of global biodiversity loss, infrastructure deterioration, and climate change. Dam management decisions can align efforts to address these crises given tools to appropriately estimate and weigh the consequences of those decisions.