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WATER RESOURCES RESEARCH, VOL. 39, NO. 3, 1066, doi:10.1029/2002WR001377, 2003

Use of hydraulic head to estimate volumetric gas content and ebullition flux in northern peatlands

Donald O. Rosenberry

U.S. Geological Survey, Lakewood, Colorado, USA

Paul H. Glaser

University of Minnesota, Minneapolis, Minnesota, USA

Donald I. Siegel

Syracuse University, Syracuse, New York, USA

Edwin P. Weeks

U.S. Geological Survey, Lakewood, Colorado, USA

Abstract

Hydraulic head was overpressured at middepth in a 4.2-m thick raised bog in the Glacial Lake Agassiz peatlands of northern Minnesota, and fluctuated in response to atmospheric pressure. Barometric efficiency (BE), determined by calculating ratios of change in hydraulic head to change in atmospheric pressure, ranged from 0.05 to 0.15 during July through November of both 1997 and 1998. The overpressuring and a BE response were caused by free-phase gas contained primarily in the center of the peat column between two or more semielastic, semiconfining layers of more competent peat. Two methods were used to determine the volume of gas bubbles contained in the peat, one using the degree of overpressuring in the middepth of the peat, and the other relating BE to specific yield of the shallow peat. The volume of gas calculated from the overpressuring method averaged 9%, assuming that the gas was distributed over a 2-m thick overpressured interval. The volume of gas using the BE method averaged 13%. Temporal changes in overpressuring and in BE indicate that the volume of gaseous-phase gas also changed with time, most likely because of rapid degassing (ebullition) that allowed sudden loss of gas to the atmosphere. Estimates of gas released during the largest ebullition events ranged from 0.3 to 0.7 mol m⁻² d⁻¹. These ebullition events may contribute a significant source of methane and carbon dioxide to the atmosphere that has so far largely gone unmeasured by gas-flux chambers or tower-mounted sensors.

Published 20 March 2003.

Index Terms: 3322 Meteorology and Atmospheric Dynamics: Land/atmosphere interactions; 1829 Hydrology: Groundwater hydrology; 1890 Hydrology: Wetlands; 1894 Hydrology: Instruments and techniques.

Subscriber Access to Full Article (Nonsubscribers may purchase for $9.00, Includes print PDF, file size: 859054 bytes)

Citation: Rosenberry, D. O., P. H. Glaser, D. I. Siegel, and E. P. Weeks (2003), Use of hydraulic head to estimate volumetric gas content and ebullition flux in northern peatlands, Water Resour. Res., 39(3), 1066, doi:10.1029/2002WR001377.

Copyright 2003 by the American Geophysical Union.