Dirtiest Snow on Record: Pollution Accelerates Snowmelt in the Wasatch Mountains

Snow is a vital resource for many regions, especially those that rely on seasonal snowmelt for their water supply.

However, snow is also vulnerable to various factors that can affect its quality and quantity, such as climate change, land use change, and dust deposition.

In this article, we will explore how dust from the Great Salt Lake and other sources impacted the snowpack in the Wasatch Mountains during the 2022 season, and what implications this has for the future of Utah's water resources.

Dust-on-snow: a growing threat to Utah's water security

(Photo : GEORGE FREY/AFP via Getty Images)

Dust-on-snow is a phenomenon that occurs when wind-blown dust particles land on the surface of snow, changing its albedo (reflectivity) and thermal properties.

Dusty snow absorbs more solar radiation than clean snow, which causes it to melt faster and earlier, as per the University of Utah.

This can have significant consequences for the hydrological cycle, as it alters the timing and magnitude of snowmelt runoff, affecting water availability, quality and ecosystem services downstream.

According to a new study by University of Utah researchers, published in the journal Environmental Research Letters, 2022 was the dirtiest snow-year in the Wasatch since observations began in 2009.

The study analyzed the impact of dust on snow during the 2022 season, using data from field measurements, satellite imagery and atmospheric modeling.

The researchers found that 2022 had the most dust deposition events (12) and the highest snowpack dust concentrations (0.8 g/m2) of any year in their record.

The dust caused the snowpack to disappear 17 days earlier than if no dust had been deposited.

The researchers said that the impact would have been more dramatic if not for the wet spring-frequent snowstorms buried the dusty layers, which delayed the impact on snowmelt.

However, they warn that if dry conditions persist in the future, dust-on-snow events could become more frequent and intense, posing a serious threat to Utah's water security.

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Dust sources: linking lake levels and snowmelt

To understand if record high dust-on-snow concentrations were linked to record low Great Salt Lake water levels, the authors identified the areas where each dust event originated, as per Phys.org.

They used a combination of satellite imagery, meteorological data and backward trajectory modeling to trace the dust plumes back to their source regions.

They found that the Great Salt Lake contributed 23% of total dust deposition and had the highest dust emissions per surface area.

The Great Salt Lake Desert and the dry lakebeds of Sevier Lake and Tule Lake contributed 45% and 17% respectively, but with lower per area emissions.

The Great Salt Lake is a terminal lake that has no outlet other than evaporation. Its water level fluctuates depending on precipitation, evaporation and diversions for human use.

In recent years, prolonged drought, increased evaporation and sustained agriculture and domestic water consumption have driven the lake to record lows in 2021 and 2022, exposing more than 50% of its lakebed.

This creates a large potential source of dust that can be easily mobilized by strong winds.

The researchers said that reducing water diversions from the Great Salt Lake could help mitigate dust emissions and preserve its ecological and economic value.

They also suggested that restoring vegetation cover on exposed lakebeds could help stabilize the soil and prevent erosion.

However, they acknowledged that these solutions are challenging to implement due to competing demands for water and land use.

Implications for water management and policy

The study by University of Utah researchers highlights the importance of monitoring and understanding dust-on-snow events in Utah, as they have significant implications for water management and policy.

Dust-on-snow accelerates snowmelt by reducing snow albedo and increasing snow temperature, which affects water availability, quality and ecosystem services downstream.

Dust-on-snow also poses a health risk for those living in Utah's most populous region, as it degrades air quality and increases respiratory problems.

The study showed that dust-on-snow events are influenced by local and regional dust sources, especially the Great Salt Lake, which has become a major dust emitter due to historically low water levels.

The researchers suggested that reducing water diversions from the lake and restoring vegetation cover on its exposed lakebeds could help reduce dust emissions and protect Utah's water resources.

However, they also recognized that these solutions require coordination among multiple stakeholders and agencies, as well as public awareness and education.

The study concluded that dust-on-snow is a growing threat to Utah's water security that needs to be addressed by integrating it into hydrological models, water management plans and policy decisions.

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