Subsurface permeability contrasts control shallow groundwater flow dynamics in the critical zone of a glaciated, headwater catchment

Groundwater flow direction within the critical zone of headwater catchments is often assumed to mimic land surface topographic gradients. However, groundwater hydraulic gradients are also influenced by subsurface permeability contrasts, which can result in variability and magnitude. In this study, we investigated relationship between shallow direction, topography, topography low units a catchment at Hubbard Brook Experimental Forest (HBEF), NH. We continuously monitored levels solum throughout several seasons well network (20 wells 0.18–1.1 m depth) upper hillslopes Watershed 3 HBEF. Water were four deeper wells, screened from 2.4 6.9 depth glacial drift C horizon. conducted slug tests across determine saturated conductivity (Ksat) materials surrounding each well. Results showed that under higher water table regimes, mimics but lower deviate as much 56 degrees topography. Under these conditions, instead followed top The interquartile range Ksat horizon was two orders magnitude than solum. Overall, our results suggest acted end members defining bounds variability. This suggests temporal dynamics should be considered when calculating hydrologic fluxes runoff generation studies underlain drift.