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Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
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Volume 22, issue 10 | Copyright
Hydrol. Earth Syst. Sci., 22, 5281-5298, 2018
https://doi.org/10.5194/hess-22-5281-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 15 Oct 2018

Research article | 15 Oct 2018

The importance of small artificial water bodies as sources of methane emissions in Queensland, Australia

Alistair Grinham1, Simon Albert1, Nathaniel Deering1, Matthew Dunbabin2, David Bastviken3, Bradford Sherman4, Catherine E. Lovelock5, and Christopher D. Evans6 Alistair Grinham et al.
  • 1School of Civil Engineering, The University of Queensland, Brisbane, 4072, Australia
  • 2Queensland University of Technology, Institute for Future Environments, Brisbane, QLD, Australia
  • 3Department of Thematic Studies–Water and Environmental Studies, Linköping University, Linköping, 58183, Sweden
  • 4CSIRO Land and Water, Canberra, 2601, Australia
  • 5School of Biological Sciences, The University of Queensland, Brisbane, 4072, Australia
  • 6Centre for Ecology and Hydrology, Environment Centre Wales, Bangor, LL57 2UW, UK

Abstract. Emissions from flooded land represent a direct source of anthropogenic greenhouse gas (GHG) emissions. Methane emissions from large, artificial water bodies have previously been considered, with numerous studies assessing emission rates and relatively simple procedures available to determine their surface area and generate upscaled emissions estimates. In contrast, the role of small artificial water bodies (ponds) is very poorly quantified, and estimation of emissions is constrained both by a lack of data on their spatial extent and a scarcity of direct flux measurements. In this study, we quantified the total surface area of water bodies <105m2 across Queensland, Australia, and emission rates from a variety of water body types and size classes. We found that the omission of small ponds from current official land use data has led to an underestimate of total flooded land area by 24%, of small artificial water body surface area by 57% and of the total number of artificial water bodies by 1 order of magnitude. All studied ponds were significant hotspots of methane production, dominated by ebullition (bubble) emissions. Two scaling approaches were developed with one based on pond primary use (stock watering, irrigation and urban lakes) and the other using size class. Both approaches indicated that ponds in Queensland alone emit over 1.6 Mt CO2 eq. yr−1, equivalent to 10% of the state's entire land use, land use change and forestry sector emissions. With limited data from other regions suggesting similarly large numbers of ponds, high emissions per unit area and under-reporting of spatial extent, we conclude that small artificial water bodies may be a globally important missing source of anthropogenic greenhouse gas emissions.

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Artificial water bodies are a major source of methane and an important contributor to flooded land greenhouse gas emissions. Past studies focussed on large water supply or hydropower reservoirs with small artificial water bodies (ponds) almost completely ignored. This regional study demonstrated ponds accounted for one-third of flooded land surface area and emitted over 1.6 million t CO2 eq. yr−1 (10 % of land use sector emissions). Ponds should be included in regional GHG inventories.
Artificial water bodies are a major source of methane and an important contributor to flooded...
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