Active rock glaciers as shallow groundwater reservoirs, Austrian Alps

Gerfried Winkler,Alexander Brodacz,Thomas Wagner,Karl Krainer

doi:10.1007/s00767-020-00455-x

Abstract

Rock glaciers are the most prominent landforms of alpine permafrost and comprise complex shallow aquifer systems in (high) alpine catchments. Recession analyses of groundwater discharge of four active rock glaciers that contain permafrost ground ice show that they have a base flow component of the order of a few liters per second, similar to that of a relict rock glacier in which permafrost ground ice is absent. This is related to an unfrozen (fine-grained) base layer with a thickness of about 10 m. Based on a threshold analysis of precipitation events and event water discharge, depressions atop the bedrock or the permafrost table seem to play only a minor role in storing groundwater. This important finding has rarely been documented, but is highly relevant for optimal groundwater resources management in sensitive (high) alpine catchments and ecosystems. All the rock glaciers analyzed here are located in the Austrian Alps and represent the nationwide sites where suitable discharge data are available. The analysis highlights the hydrogeological importance of these discrete permafrost-derived debris accumulations as complex shallow groundwater bodies with important—but limited—storage and buffer capabilities.

Highlights

The impact of climate warming on glacier retreat in mountainous regions of the world and their runoff has been a subject of intense research during recent decades (e.g. Neal et al 2010; Huss 2011; Huss and Hock 2018; Shannon et al 2019)
Discharge data of all active rock glacier springs show highest discharge values of more than 500 l/s with a maximum of 718 l/s at OEG (Table 2). These values are approximately twice of the maximum discharge at the relict rock glacier SRG (Table 2), which has about half of the catchment size compared to the active rock glaciers (Table 1)
Based on the analyses presented above, we assume that active as well as relict rock glaciers may have a considerable base flow component that is related to a relatively finegrained unfrozen base layer, which may provide groundwater storage and buffer capabilities affecting discharge patterns of alpine headwaters

Summary

Introduction

The impact of climate warming on glacier retreat in mountainous regions of the world and their runoff has been a subject of intense research during recent decades (e.g. Neal et al 2010; Huss 2011; Huss and Hock 2018; Shannon et al 2019). Following the expectation that most of the glaciers will disappear by the end of the century in mountainous regions, permafrost, and rock glaciers as their most prominent landforms, will likely gain in importance in the mountain cryosphere and become even more important for ecosystem services provision (Grêt-Regamey et al 2012; Harrington et al 2017). This is to be anticipated, because permafrost ground ice in rock glaciers, which is protected by a thick debris layer, is melting at much smaller rates compared to ice glaciers (Jones et al 2019)

Results

Discussion

Conclusion