HR: 17:30h
AN: H34C-07    [Abstracts]
TI: Deforestation and Gravel Pits on the Boreal Plains: What Influence Does Enhanced Recharge Have in a Land of Evaporation Windows?
AU: * Smerdon, B D
EM: bsmerdon@UAlberta.ca
AF: Department of Earth and Atmospheric Sciences, University of Alberta, 1-26 Earth Sciences Bldg, Edmonton, AB T6G 2E3 Canada
AU: Mendoza, C A
EM: Carl.Mendoza@UAlberta.ca
AF: Department of Earth and Atmospheric Sciences, University of Alberta, 1-26 Earth Sciences Bldg, Edmonton, AB T6G 2E3 Canada
AU: Devito, K J
EM: Kevin.Devito@UAlberta.ca
AF: Department of Biological Sciences, University of Alberta, Z 914 Biological Sciences Bldg, Edmonton, AB T6G 2E9 Canada
AB: The impact of landscape disturbance within a Boreal outwash plain in Northern Alberta, Canada, was determined from hydrologic and stable isotopic measurements (oxygen and hydrogen), and a three-dimensional watershed flow model. On the hummocky, outwash landscape, these Boreal lakes, wetlands, and ponds are maintained by interaction with regional groundwater flow systems. The sub-humid climate causes lakes and ponds to function as evaporation windows, capturing local groundwater and releasing it to the atmosphere in summer months. During a 3-year water budget study, in drought conditions, a strong shift toward meteoric concentrations of the stable isotopic composition of both lake water and groundwater discharge was detected in a lake located downgradient of a previously forested esker (10 m high), which had been recently excavated for mineral aggregate (i.e., sand and gravel). We used two- and three-dimensional numerical flow and transport models to simulate the transient response of groundwater-lake interaction, and investigate scenarios of enhanced recharge caused by deforestation, and excavation of the gravel pit within the past decade. Hydrologic field observations (including transient water table and lake level responses), and stable isotopic analyses enabled development of a numerical flow model that required minimal calibration. We find that most of enhanced groundwater recharge occurs because of deforestation, rather than removal of approximately 10 m of esker material. Therefore, under a similar climate, groundwater recharge rates could return to pre-construction conditions if the gravel pit were reclaimed with a forested ecosystem. The integrative use of hydrologic and isotopic field measurements, and a robust numerical model, was paramount in determining the influence of landscape disturbance within this Boreal watershed. This work illustrates the importance of location of landscape disturbance within a flow system, and is guiding development of adaptive land management practices (e.g. access road development), and reclamation projects in the Boreal Plains region.
DE: 1803 Anthropogenic effects (4802, 4902)
DE: 1830 Groundwater/surface water interaction
DE: 1832 Groundwater transport
DE: 1847 Modeling
DE: 1890 Wetlands (0497)
SC: Hydrology [H]
MN: Fall Meeting 2005