Mechanisms linking active rock glaciers and impounded surface water formation in high‐mountain areas

Abstract

Rock glaciers are slowly flowing mixtures of debris and ice occurring in mountains. They can represent a reservoir of water, and melting ice inside them can affect surface water hydrochemistry. Investigating the interactions between rock glaciers and water bodies is therefore necessary to better understand these mechanisms. With this goal, we elucidate the hydrology and structural setting of a rock glacier–marginal pond system, providing new insights into the mechanisms linking active rock glaciers and impounded surface waters. This was achieved through the integration of waterborne geophysical techniques (ground penetrating radar, electrical resistivity tomography and self‐potentials) and heat tracing. Results of these surveys showed that rock glacier advance has progressively filled the valley depression where the pond is located, creating a dam that could have modified the level of impounded water. A sub‐surface hydrological window connecting the rock glacier to the pond was also detected, where an inflow of cold and mineralised underground waters from the rock glacier was observed. Here, greater water contribution from the rock glacier occurred following intense precipitation events during the ice‐free season, with concomitant increasing electrical conductivity values. The outflowing dynamic of the pond is dominated by a sub‐surface seepage where a minor fault zone in bedrock was found, characterised by altered and highly‐fractured rocks. The applied approach is evaluated here as a suitable technique for investigating logistically‐complex hydrological settings which could be possibly transferred to wider scales of investigation. Copyright © 2017 John Wiley & Sons, Ltd.

Prokaryotic Diversity and Distribution in Different Habitats of an Alpine Rock Glacier-Pond System

“…Moreover, the limited dimensions potentially increase its susceptibility to external environmental pressures [18,19]. The presence of a localised inflow from the RG has been confirmed [17], but it is important to specify that these meltwater inputs have been described as intermittent, concentrated only in the snow-free season and mainly linked to precipitation events [17,20]. Meltwaters also showed only a moderate increase in solutes concentration if compared with the pond waters [20], differing in this sense from other RGlake/stream systems affected by natural acid rock drainage phenomena [9,14,15].…”

“…The pond has an area of 1,600 m 2 , with maximum length and width of approximately 60 x 40 m, and reaches a maximum depth of about 3 m. It is a clear-water pond, characterised by oligotrophic conditions and by the lack of macroalgal and macrophyte cover on the bottom, with the shallower areas close to the shore undergoing seasonal freezing. More details on the catchment structural settings and hydrological dynamics of the pond are described in Colombo et al [17,20]. The research site is a node of the Long-Term Ecological Research (LTER) network in Italy (http://www.lteritalia.it).…”

“…However, the obtained data still offered some insights on the overall ecosystem relations between geochemistry and microbial community composition. For instance, our initial hypothesis was that the presence of RG hydrological inputs into the pond documented by Colombo et al [17,20], although limited in time and magnitude, would have led to a differentiation of sediments closest to the RG front from the farther ones.…”

“…In this study, we focused on a RG-pond system located in North-western Italian Alps, whose structural settings and hydrological dynamics have been previously described by Colombo et al [17]. This pond represents for many reasons a suitable model system to investigate the influence of RGs on downstream aquatic ecosystems.…”

Periglacial water paths within a rock glacier‐dominated catchment in the Stepanek area, Central Andes, Mendoza, Argentina

“…Cryogenic and chemical processes such as cryoweathering, oxidation and reduction enhance these changes in the active layer and in the permafrost table. Colombo et al studied a pond located at the front of a rock glacier in the north‐western Italian Alps that is progressively filled by the advancing rock glacier. The outflow of the pond was considered to be dominated by subsurface seepage with a minor fault zone, characterized by the presence of altered and highly fractured rock in the bedrock.…”