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TEMPORAL AND SPATIAL PATTERNS OF METHANE EMISSIONS FROM A RESERVOIR DRAINING AN AGRICULTURAL WATERSHED
Citation:
Beaulieu, J., C. Nietch, M. McManus, AND A. Townsend-Small. TEMPORAL AND SPATIAL PATTERNS OF METHANE EMISSIONS FROM A RESERVOIR DRAINING AN AGRICULTURAL WATERSHED. Presented at ALSO Aquatic Sciences Meeting, Granada, SPAIN, February 22 - 27, 2015.
Impact/Purpose:
To inform the public.
Description:
We used multiple approaches to characterize temporal and spatial patterns in methane (CH4) emissions from a mid-latitude reservoir (William H. Harsha Lake, Ohio, USA) draining an agricultural watershed. Weekly to monthly monitoring at six sites in the reservoir during a 13 month period revealed that emission rates were highly seasonal, with the highest rates occurring during the summer and lowest during the winter. Spatial patterns were quantified by allocating 115 sampling sites among “open-water” and “tributary-associated” portions of the reservoir using a generalized random tessellation stratified (GRTS) survey design. GRTS survey designs utilize a spatially balanced sampling pattern to generate mean and variance estimates at the strata or whole-system scale. Methane emission rates from tributary-associated portions of the reservoir were greater than those of open-water areas (p < 0.001) and exceeded 150 mg CH4 m-2 h-1 where bubbling was observed. Despite their limited spatial extent, the tributary-associated areas were an important component of the reservoir-scale emission rate. The combination of GRTS surveys and seasonal sampling provides an effective approach for quantifying spatial and temporal variation in CH4 emission rates.
