Interactions Between Regional Climate, Surficial Geology, and Topography: Characterizing Shallow Groundwater Systems in Subhumid, Low-Relief Landscapes

摘要

The Boreal Plains region of Canada is characterized by low relief, heterogeneous glacial landforms, and a subhumid climate, which result in complex and spatially variable groundwater-surface water interactions. We test the influence of, and interactions between, short-term climate variations, glacial deposit types, and topography on water table position and groundwater flow in a region with a subhumid long-term climate. To do so, we evaluated water table positions, vertical hydraulic gradients, geochemistry, and stable water isotope signatures over a 19-year period (including wet and dry climate states) along a 70-km transect. The transect spans topographic positions on three hydrological response areas that comprise the major glacial depositional types typical of the Boreal Plains. High spatiotemporal variability of water table fluctuations and responses to climate signals illustrate the strong spatially variable controls that surficial geology, climate, and topography exert over scales of groundwater flow within and between glacial landforms across the Boreal Plains. Water tables were determined to be recharge controlled in the hummocky moraine and coarse outwash and topography controlled in the clay plain. Chemoscapes and isoscapes help delineate areas with characteristic water storage and transmission properties, which in turn control scales of groundwater flow and hydrologic responses to climate. Understanding the natural spatial and temporal variability of, and controls on, water table position, groundwater movement, and water quality under varying physical and climatic scenarios is important, as water security, ecosystem sustainability, and environmental quality become the focus of land management and reclamation efforts.