The influence of climate on water cycling and lake-groundwater interaction in an outwash landscape on the Boreal Plains of Canada

The influence of climate and land use on water cycling and lake-groundwater interaction were determined for a glacial outwash landscape on the Boreal Plains of Canada. Increased landscape disturbance (from logging activity, road building, and gravel pit construction) and a need to assess potential climate change effects, initiated study of hydrological processes at a lake in the Utikuma Research Study Area (URSA). The URSA has a sub-humid climate (P ≤ PET), which controls many hydrological processes. Lake-groundwater interaction was quantified, climatic influence on groundwater recharge was investigated, and the influence of landscape disturbance on lake source water was determined.; On hummocky, poorly drained, outwash landscapes, surface water and wetlands are maintained by groundwater flow systems. Hydrometric measurements and stable isotopic analyses of waters collected during a 3-year lake budget study indicate that evaporation was the dominant hydrologic flux in summer months. The onset and duration of evaporation from the lake was a major controlling factor on groundwater exchange, to such a degree that the shallow lakes function as evaporation windows in this landscape, creating groundwater capture zones. Transient hydrologic responses of the flow-through lake and three-dimensional groundwater flow were simulated to study controls on lake-groundwater interaction. Replication of the flow regime required both an anisotropy ratio of 10:1 for the outwash deposits and the inclusion of storage effects within riparian peatlands. These peatlands govern lake-groundwater interaction and maintain surface water on permeable northern landscapes.; The control of spatially and temporally variable groundwater recharge and evapotranspiration processes on groundwater recharge was investigated through development of one- and two-dimensional models of variably-saturated flow. Groundwater recharge and upflux from the water table were found to depend on climate history and water table depth. In summer months, when transpiration and canopy interception were considered explicitly, groundwater recharge was negligible, and groundwater was predicted to be drawn vertically upward due to evapotranspiration. Simulations of isotopic transport identified that localized landscape disturbance has started to alter the water source to the study lake, and that climate and groundwater flow transience must be considered when applying isotope-mass balance approaches for quantifying hydrological processes on the Boreal Plains.