Effects of an experimental water-level drawdown on methane emissions from a eutrophic reservoir
Citation:
Beaulieu, J., A. Balz, M. Birchfield, J. Harrison, C. Nietch, M. Platz, W. C. SQUIER, S. Waldo, Johnt Walker, K. White, AND J. Young. Effects of an experimental water-level drawdown on methane emissions from a eutrophic reservoir. ECOSYSTEMS. Springer, New York, NY, 21(4):657-674, (2018).
Impact/Purpose:
Reservoirs are a globally significant source of methane (CH4) to the atmosphere. However, emission rate estimates may be biased low due to inadequate monitoring during brief periods of elevated emission rates (i.e. hot-moments). Here we investigate CH4 bubbling (i.e. ebullition) during periods of falling water-levels in a eutrophic reservoir in the midwestern United States. We hypothesized that periods of water level decline trigger the release of CH4 rich bubbles from the sediments and that these emissions constitute a substantial fraction of the annual CH4 flux. We explored this hypothesis by monitoring CH4 ebullition in a eutrophic reservoir over a 7 month period which included an experimental water level drawdown. We found that the ebullitive CH4 flux rate was among the highest ever reported for a reservoir (mean = 882 mg CH4 m-2 d-1). The already high ebullitive flux rates increased by factors of 1.4 – 77 across the 9 monitoring sites during the 24 hour experimental water level drawdown, but these emissions constituted only 6% of the CH4 flux during the 7-month monitoring period due to high ebullitive CH4 flux rates throughout the warm weather season. While drawdown emissions were found to be a minor component of annual CH4 emissions in this reservoir, our findings demonstrate a link between water-level change and CH4 ebullition, suggesting that CH4 emissions may be mitigated through water-level management in some reservoirs.
Description:
Reservoirs are a globally significant source of methane (CH4) to the atmosphere. However, emission rate estimates may be biased low due to inadequate monitoring during brief periods of elevated emission rates (i.e. hot-moments). Here we investigate CH4 bubbling (i.e. ebullition) during periods of falling water-levels in a eutrophic reservoir in the midwestern United States. We hypothesized that periods of water level decline trigger the release of CH4 rich bubbles from the sediments and that these emissions constitute a substantial fraction of the annual CH4 flux. We explored this hypothesis by monitoring CH4 ebullition in a eutrophic reservoir over a 7 month period which included an experimental water level drawdown. We found that the ebullitive CH4 flux rate was among the highest ever reported for a reservoir (mean = 882 mg CH4 m-2 d-1). The already high ebullitive flux rates increased by factors of 1.4 – 77 across the 9 monitoring sites during the 24 hour experimental water level drawdown, but these emissions constituted only 6% of the CH4 flux during the 7-month monitoring period due to high ebullitive CH4 flux rates throughout the warm weather season. While drawdown emissions were found to be a minor component of annual CH4 emissions in this reservoir, our findings demonstrate a link between water-level change and CH4 ebullition, suggesting that CH4 emissions may be mitigated through water-level management in some reservoirs.
URLs/Downloads:
https://link.springer.com/article/10.1007/s10021-017-0176-2?wt_mc=Internal.Event.1.SEM.ArticleAuthorAssignedToIs
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