EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Constraining the contribution of rock glaciers to the summer hydrology of a high-elevation watershed, Uinta Mountains, Utah, USA

Jeffrey Munroe1 and Alexander Handwerger2
Jeffrey Munroe and Alexander Handwerger
  • 1Middlebury College, Geology, Middlebury, United States of America (
  • 2Jet Propulsion Laboratory, California Institute of Technology, Pasadena, United States of America (

Rock glaciers are common components of mountain landscapes with strong potential to document past and present environmental changes, and a notable vulnerability to future climatic perturbations.  Recent studies have begun to consider the contribution of rock glaciers to high mountain hydrology, with a particular emphasis on the possible role of internal ice as a source of meltwater.  This project utilized automated samplers to collect water discharging from two representative rock glaciers in the Uinta Mountains of Utah, USA.  Additional samplers were deployed at a non-rock glacier spring and along the main stream in this basin.  All samplers ran continuously from the start of July through early October, 2021.  Water from the automated samplers, and from precipitation collectors, was analyzed for stable isotopes with cavity ring-down spectroscopy and hydrochemistry with ICP-MS.  Our findings reveal that water draining from the rock glaciers in mid-summer has a low solute content and notably negative δ18O, consistent with the melting of lingering snowpack.  As summer progresses, values of δ18O rise and total dissolved load increases as the influence of this snow-derived water wanes.  In late summer and early autumn, nearly all of the rock glacier discharge can be distinguished from snowmelt, summer precipitation, and groundwater by intermediate values of δ18O, elevated d-excess, and high abundances of Ca and Mg.  This water is interpreted to come from internal ice that was vulnerable to melting in this warm summer following a snow-poor winter.  The isotopic and hydrochemical fingerprint of this rock glacier discharge can then be used as an end-member, along with groundwater and summer precipitation, for unmixing of the late summer streamwater composition.  This exercise suggests that September discharge in the stream, with a watershed of ~50 km2 above the sampling point, contains a detectable component derived from melting internal ice of unknown age within rock glaciers.  An important implication of this conclusion is that late summer/ autumn baseflow in high-elevation streams could decrease in the future as this reservoir of subsurface ice is depleted, particularly in summers following low-snow winters.

How to cite: Munroe, J. and Handwerger, A.: Constraining the contribution of rock glaciers to the summer hydrology of a high-elevation watershed, Uinta Mountains, Utah, USA, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3178,, 2022.


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