Examining the variability of rock glacier meltwater in space and time in high-elevation environments of Utah, United States

Rock glaciers are common geomorphic features in alpine landscapes and comprise a potentially significant but poorly quantified water resource. This project focused on three complementary questions germane to rock glacier hydrology: 1) Does the composition of rock glacier meltwater vary from year to year? 2) How dependent is the composition of rock glacier meltwater on lithology? And 3) How does the presence of rock glaciers in a catchment change stream water chemistry? To address these questions, we deployed automated samplers to collect water from late June through mid-October 2022 in two rock-glacierized mountain ranges in Utah, United States characterized by different lithologies. In the Uinta Mountains of northern Utah, where bedrock is predominantly quartzite, water was collected at springs discharging from two rock glaciers previously shown to release water in late summer sourced from internal ice. In the La Sal Mountains of southeastern Utah, where trachyte bedrock is widespread, water was collected at a rock glacier spring, along the main stream in a watershed containing multiple rock glaciers, and from a stream in a watershed where rock glaciers are absent. Precipitation was also collected, and data loggers for water temperature and electric conductivity were deployed. Water samples were analyzed for stable isotopes with cavity ring-down spectroscopy and hydrochemistry with ICP-MS. Our data show that water discharging from rock glaciers in the Uinta Mountains exhibits a shift from a snowmelt source to an internal ice source over the course of the melt season that is consistent from year to year. We also found that the chemistry of rock glacier water in the two study areas is notably different in ways that can be linked back to their contrasting bedrock types. Finally, in the La Sal Mountains, the properties of water along the main stream in a rock-glacierized basin resemble the properties of water discharging from rock glaciers, and strongly contrast with the water in a catchment lacking rock glaciers. Collectively these results underscore the role of rock glaciers as an agent influencing the hydrochemistry of water in high-elevation stream systems.

Automated summary

Rock glaciers are common in alpine landscapes and play an important role as a poorly quantified water resource. This study focused on three questions regarding rock glacier hydrology: 1) Does the composition of rock glacier meltwater vary annually? 2) How does the composition of rock glacier meltwater depend on bedrock type? And 3) How do rock glaciers in a catchment affect stream water chemistry? The researchers collected water samples from two rock-glacierized mountain ranges in Utah, United States, with different lithologies. The results show that the water composition of rock glaciers in the Uinta Mountains shifts from a snowmelt source to an internal ice source throughout the melting season, consistently across years. The study also found notable differences in the chemistry of rock glacier water between the two study areas, which can be linked to the contrasting bedrock types. These findings emphasize the influence of rock glaciers on the hydrochemistry of high-elevation stream systems.