We examined how best management practices (BMP) for large-scale aspen harvest emulating wildfire affects the regional hydrology of streams on the Boreal Plains. A paired-catchment before-after control-impact (BACI) study of runoff was employed on two meso-scale catchments (>10 km2) with second-order streams and approximately 50% aspen cover. Within the harvest catchment, greater than 80% (~400 ha) of the aspen was clear-cut over two summers. Runoff was low (<45 mm*yr-1) and there was no statistical change in annual flow for either catchment in the three years prior to and following harvest. Harvest impacts were confounded by inter-annual variations in precipitation resulting in large variations in depression and groundwater storage within both harvested and intact forests. Rapid regeneration of clonal aspen and dominance of summer rainfall resulted in rapid recovery of antecedent moisture. Heterogeneity of glacial deposits and land cover, and the mosaic of surface storage associated with large catchments, interacted to further confound the impact of aspen harvest on stream flow. Harvest areas were located on moraines with large potential storage and limited hydrologic connectivity. In contrast, headwater and alluvial valley peatlands, which were the predominant runoff generating areas, were minimally disturbed. Finally, beaver activity with ten dams per kilometre of stream length plus dam breakage influenced base flows, and peak flows independent of harvesting. This study demonstrates the critical need to consider climate, geology, beaver, and scale of activity for generalizing the impact of harvesting and the efficacy of BMPs across Plains, Montane and Shield ecosystems of the Boreal Forest.