Field characterization of hydraulic conductivity in a heterogeneous alpine glacial till

Three different measurement techniques (a mini-disk infiltrometer, a double-ring infiltrometer, and a Guelph permeameter) were used to characterize the saturated hydraulic conductivity of an alpine glacial till in the Rocky Mountains of southern Wyoming, USA. Measurements from 32 locations reveal significant spatial heterogeneity. The hydraulic conductivity varies over two orders of magnitude from approximately 0.05–5 m/d. Along with natural variability throughout the study area, the results also indicate that the estimated hydraulic conductivity is dependent on measurement technique. Compared to the mini-disk infiltrometer, hydraulic conductivities are consistently higher for the double-ring infiltrometer and Guelph permeameter. By considering surface–subsurface hydrologic response during snowmelt, we demonstrate the importance of accurately characterizing the hydraulic conductivity. A model parameterized with a low hydraulic conductivity underestimates the rate of shallow groundwater flow, suggesting that the subsurface saturated zone may not be able to accommodate all of the snowmelt-derived recharge. Saturation-excess overland flow is predicted as a result. These findings have important implications for integrated hydrologic assessments focused on understanding water flows in glaciated alpine watersheds.