Abstract:Understanding groundwater processes in alpine watersheds is critical to understand the timing of water release and late-season stream flow for both headwater and downstream environments. Moraines and talus features can play an important role in groundwater flow and storage processes in alpine watersheds, but neither process is well understood for these features. We examined the complex hydrogeological environment of a partially ice-cored moraine in the Lake O'Hara watershed in the Canadian Rockies. Electrical resistivity imaging (ERI) and seismic refraction tomography delineated regions of buried ice and frozen and unfrozen moraine material. Seismic refraction data also clearly indicated the depth to bedrock, which varied primarily due to the thickness of the overlying moraine material. Water levels in a lake and several tarns on the moraine responded differently to inputs of rain, snowmelt, and glacier melt, indicating the different degree of hydrological connectivity of these features to the groundwater flow system in the moraine. Such differences reflect the effects of bedrock topography and the location and geometry of buried ice. Ground-penetrating radar images and ERI indicated regions of perched groundwater and focused infiltration. The location of these regions appears to be controlled by buried ice. All geophysical and hydrological data suggest that a relatively thin (<5 m) layer of saturated sediments and/or fractured bedrock likely provides a major flow system within the moraine.

[1] Recent studies in mountain environments have indicated that groundwater represents a major component of the water balance of alpine streams and lakes. However, the scarcity of information on the hydraulic properties of geological materials in alpine environments presents a major obstacle to understanding the response of these watersheds to hydrological inputs and their future variability. The information is particularly limited for talus and proglacial moraine, where rugged topography prohibits the installation of groundwater monitoring wells. Observation of groundwater-surface water interaction provides a useful tool for studying groundwater in these challenging environments. Here we present a unique experiment using a tarn (i.e., pond on proglacial moraine) in a partially glaciated watershed in the Canadian Rockies as a surrogate for a groundwater monitoring well. A chloride dilution test and detailed energy balance monitoring were simultaneously conducted to quantify the groundwater-surface water interactions. The water balance of the tarn was dominated by groundwater inflow and outflow, ranging between 70 and 720 m 3 d À1 , while the volume of the water in the tarn fluctuated between 140 and 620 m 3 . Comparing the observed flow rates with a semianalytical solution of groundwater interactions with a flowthrough pond, the hydraulic conductivity of the proglacial moraine is estimated to be in the order of 10 À3 m s À1 , which provides one of the very few measurements of large-scale hydraulic conductivity of proglacial moraine. The study demonstrates a useful application of mass and energy balance measurements in rugged environments and provides the essential information for advancing our understanding of alpine groundwater hydrology.Citation: Langston, G., M. Hayashi, and J. W. Roy (2013), Quantifying groundwater-surface water interactions in a proglacial moraine using heat and solute tracers, Water Resour. Res., 49,[5411][5412][5413][5414][5415][5416][5417][5418][5419][5420][5421][5422][5423][5424][5425][5426]

With the changing precipitation patterns and melting of mountain glaciers and permafrost that result from global warming, information on the distribution of groundwater in mountainous terrains is becoming increasingly important for developing prudent resource and hazard management strategies. Obtaining this information across topographically craggy and variably frozen ground in a cost-effective and nonintrusive manner is challenging. We introduce a modified 2D surface nuclear magnetic resonance (NMR) tomographic technique that allows us to account for substantial variations in surface topography in locating and quantifying groundwater occurrences in rugged mountains. Because contact with the ground is not necessary, it is a rare geophysical technique not affected by sensor-to-ground coupling problems common in high mountain environments. To demonstrate the efficacy of the tomographic imaging scheme, we invert a large multioffset surface NMR data set collected across a partially ice-cored proglacial terminal moraine in the Canadian Rocky Mountains. Our preferred model contains a 2- to 5-m-thick water layer, the top of which has practically the same elevation as the surface of a nearby lake and the bottom of which coincides with bedrock resolved in companion seismic and ground-penetrating radar studies.