HESSD Hydrology and Earth System Sciences Discussions HESSD Hydrol. Earth Syst. Sci. Discuss. 1812-2116 Göttingen, Germany 10.5194/hessd-2-483-2005 Hydrogeomorphic controls on runoff in a temperate swamp Kaufman S. C. 1 Waddington J. M. 1 Branfireun B. A. 2 McMaster University, School of Geography and Geology, 1280 Main Street West, Hamilton, Ontario L8S 4K1, Canada University of Toronto at Mississauga, Department of Geography, 3359 Mississauga Road North, Mississauga, Ontario L5L 1C6, Canada 11 04 2005 2 2 483 508 Copyright: © 2005 S. C. Kaufman et al. 2005 This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 2.5 Generic License. To view a copy of this licence, visit https://creativecommons.org/licenses/by-nc-sa/2.5/ This article is available from https://hess.copernicus.org/preprints/2/483/2005/hessd-2-483-2005.html The full text article is available as a PDF file from https://hess.copernicus.org/preprints/2/483/2005/hessd-2-483-2005.pdf

Beverly Swamp, a high-order forested temperate wetland near Hamilton, Ontario was studied during wet (2000) and dry (2001) summer seasons to determine and compare runoff pathways and storage mechanisms in two hydrogeomorphically different sub-basins. A channelized (Fletcher Swamp) and an unchannelized (Spencer Swamp) sub-basin were examined. During wet periods, the Fletcher Swamp displayed a consistent interaction between the wetland and stream, resulting in a gaining stream, maintaining a lateral hydrological connection and yielding high runoff ratios. When dry periods dominated, water tables dropped low enough in the Fletcher Swamp such that water moved from the stream channel into the underlying substrate, creating a lateral hydrological disconnection between the stream and wetland. This disconnection reduced runoff ratios during storm events. The Spencer Swamp, with no well-defined stream channel, relied on overland flow and a longitudinal hydrological connection to deliver water to the sub-basin outflow. This connection was maintained in the wet season (2000) but ceased in the dry season (2001) despite consistent inputs from an upstream reservoir. Available depression storage prevented overland flow during 2001, and although a shallow groundwater flux maintained discharge for a period of time, drought conditions led to zero discharge at the sub-basin outflow in mid-summer. Runoff ratios were reduced dramatically from season to season as a result of this disconnection. Implications of these hydrogeomorphic runoff controls on wetland biogeochemistry are discussed.