Declining Great Salt Lake and Exceptional Drought: Impacts on Dust Sources and Transport in Eastern Great Basin, USA

Dust transport in the eastern Great Basin, located in western Utah and eastern Nevada, is a hazard for air quality, transportation, water supply, and ecosystems. This region experiences distinct seasonal patterns in dust transport driven by pre and post frontal winds associated with intermountain cyclones in the spring and fall and outflow winds from monsoonal thunderstorms in the summer. Dust sources include playas and dry lake beds remnant from Pleistocene Lake Bonneville, agricultural areas, mining operations, and construction sites. In recent decades the eastern Great Basin has experienced several disturbance events, both natural and human caused, including wildfire, post-fire “rehabilitation”, exceptional drought, and decline of Great Salt Lake (the 8th largest endorheic lake in the world). This study identifies changes to dust transport frequency, severity, and source locations during the period 2000-2022 in response to these various disturbance events. Climatological identification of dust event days (DEDs) and dust event hours (DEHs) utilized weather codes indicating dust at the Salt Lake City, Salt Lake City International Airport, UT ASOS/AWOS weather station (KSLC). KSLC DEDs and DEHs showed a clear bi-modal pattern on an annual basis, with increases in frequency following disturbance events (e.g. wildfire, exceptional drought). Seasonal patterns were present, however dust transport was observed in all seasons at some point during the study period. Composites of synoptic weather conditions on DEDs created from North American Regional Reanalysis (NARR) data show the dominant weather pattern to be a mid and upper level low pressure system approaching Utah and associated southwest winds. However, there are distinct seasonal and even level variations to this dominant pattern. Source identification utilized satellite imagery from Advanced Baseline Imager (ABI), Moderate Resolution Imaging Spectroradiometer (MODIS), and Visible Infrared Imaging Radiometer Suite (VIIRS) instruments (onboard GOES-East, Terra and Aqua, and SNPP and NOAA-20 satellites, respectively) during DEDs. DED dust plume sources were identified for 82 DEDs during the study period. Kernel density analysis of dust plume source locations indicates a high density of sources to the south and west of Salt Lake City, UT, with specific sources in this area including Sevier Dry Lake, Tule Dry Lake, Wah Wah Valley Hardpan, smaller playa areas, and agricultural areas near Delta, UT. Additionally, at lower density, dust sources were identified within and adjacent to the eastern Great Basin in locations including shoreline of Great Salt Lake, Great Salt Lake Desert, playas in Nevada, and agricultural areas in the Snake River Plain in Idaho. This indicates the large number and variety of dust sources contributing to dust transport in the eastern Great Basin. Natural and human disturbance is a driver of dust transport in this region, which has been highlighted by recent media attention and public awareness of the decline of Great Salt Lake and increased dust transport from that source. Decline of Great Salt Lake in recent decades is driven by consumptive water use by agriculture, municipalities, and industry, with climate variability such as snowpack, runoff, temperature, humidity, and evaporation rates being additional factors accounting for variability. While Great Salt Lake is not the only dust source impacting the populations of Utah, it is directly adjacent to the Wasatch Front, the most densely populated corridor in the state. This attention has shed light for many Utahns on the hazards of dust on human health, and provides an opportunity for more public awareness and protective actions during dust transport events and hazardous air quality events.