Influence of a rock glacier spring on the stream energy budget and cold‐water refuge in an alpine stream

Abstract

The thermal regimes of alpine streams remain understudied and have important implications for cold‐water fish habitat, which is expected to decline due to climatic warming. Previous research has focused on the effects of distributed energy fluxes and meltwater from snowpacks and glaciers on the temperature of mountain streams. This study presents the effects of the groundwater spring discharge from an inactive rock glacier containing little ground ice on the temperature of an alpine stream. Rock glaciers are coarse blocky landforms that are ubiquitous in alpine environments and typically exhibit low groundwater discharge temperatures and resilience to climatic warming. Water temperature data indicate that the rock glacier spring cools the stream by an average of 3 °C during July and August and reduces maximum daily temperatures by an average of 5 °C during the peak temperature period of the first two weeks in August, producing a cold‐water refuge downstream of the spring. The distributed stream surface and streambed energy fluxes are calculated for the reach along the toe of the rock glacier, and solar radiation dominates the distributed stream energy budget. The lateral advective heat flux generated by the rock glacier spring is compared to the distributed energy fluxes over the study reach, and the spring advective heat flux is the dominant control on stream temperature at the reach scale. This study highlights the potential for coarse blocky landforms to generate climatically resilient cold‐water refuges in alpine streams.

After the peak water: the increasing influence of rock glaciers on alpine river systems

“…Although not capable of cooling waters in the tributary, as found by Harrington et al () in a glacier‐free catchment, the rock glacial stream does represent an important driver within the river continuum at Zay. This is demonstrated by the rise of EC below the confluence during the recession phase compared with previous periods, which can be explained by the increased contribution of permafrost‐influenced waters from the rock glacier.…”

“…Solute concentrations typically increase from spring to autumn, when the baseflow can be sustained by thawing internal ice (see Colombo et al, ). Due to their cold waters, rock glacial streams were found to decrease summer water temperature in tributaries along the river continuum, thus extending refuge areas for cold‐adapted species (Harrington, Hayashi, & Kurylyk, ). In general, rock glaciers (including fossil forms, i.e., those without ice) and other landscape features including talus bodies, moraines, and tills represent important groundwater sources (Clow et al, ; Harrington, Mozil, Hayashi, & Bentley, ; Rogger et al, ; Wagner, Pauritsch, & Winkler, ; Winkler et al, ) that are able to influence the quantity and quality of running waters in alpine catchments (Engel et al, ; Liu, Williams, & Caine, ; Weekes, Torgersen, Montgomery, Woodward, & Bolton, ).…”

Application of distributed temperature sensing for mountain permafrost mapping

“…The rock glacier is interpreted to be inactive and relatively ice‐poor based on the patchy distribution of permafrost within, the presence of finer grained soils and vegetation in some areas, and a locally shallow front angle . Groundwater discharge from the rock glacier catchment to a stream generates a cold‐water refuge for fish during summer, and is the primary source of streamflow in upper Helen Creek during winter months …”

“…26 Groundwater discharge from the rock glacier catchment to a stream generates a cold-water refuge for fish during summer, and is the primary source of streamflow in upper Helen Creek during winter months. 26,29 The internal structure of the Helen Creek rock glacier has previously been investigated using multimethod geophysical imaging and a conventional BTS approach using miniature temperature dataloggers. 26 The generalized conceptual stratigraphic model of the rock glacier is a mantle of large boulders overlying sediments hosting patches of ground ice, with either finer grained sediments or weathered and fractured bedrock at its base.…”

Groundwater flow and storage processes in an inactive rock glacier

“…The northern portion of the rock glacier is drained by a spring, which discharges into Helen Creek (Figure c). Previous manual discharge gauging profiles in the reach of Helen Creek along the rock glacier toe showed that diffuse groundwater discharge from the rock glacier to the creek is minimal; thus, presumably all rock glacier groundwater outflow occurs discretely at the spring (Harrington, Hayashi, & Kurylyk, ). The apparent catchment of the rock glacier spring is estimated to be ~0.4 km 2 based on surface topography, of which ~0.12 km 2 is occupied by the rock glacier (Figure c).…”