ACQUIRING BATHYMETRIC LIDAR DATA IN LAKE SYSTEMS: LESSONS LEARNED AND BEST PRACTICES FROM GREAT SALT LAKE AND BEAR LAKE, UTAH

Great Salt Lake (GSL) in northern Utah is a large intermontane saline lake that hosts a unique natural ecosystem but is also important for recreation and mineral extraction. A detailed understanding of the GSL lakebed would be invaluable for researchers studying its ecology, natural resources, and relationship to local geology and geologic hazards. Because the lake elevation has recently reached historic lows, posing threats to the ecosystem and surrounding communities, accurate modeling of lakebed exposure and changing water volumes is critical.

Similar to terrestrial high-resolution topographic lidar, bathymetric lidar can be used to quantify, monitor, and track changes in subaqueous environments. The Utah Geological Survey (UGS) is investigating the application of bathymetric lidar to improve models of the bed of GSL and assess the technology’s utility in a challenging saline lake environment.

In spring 2023, the UGS collected airborne bathymetric lidar data with a Leica Chiroptera 4x sensor over a pilot study area of 130 square km in the south arm on the west side of Antelope Island. Environmental conditions including wind, water clarity, water depth, lakebed reflectance, biologic activity, and other factors can affect the number of bathymetric bottom returns. Overall, the survey obtained bottom returns over only 28% of the surveyed area. At depths less than 3 m in the shallow shelf environment, the survey shows sub-meter topographic relief, highlighting structures such as microbialite reefs and possible newly discovered spring-related carbonate mounds. However, bottom returns were not reliably detected at depths greater than 3–4 m.

More recently, the UGS collected reconnaissance data along single flight paths across GSL and Bear Lake using a more powerful sensor, the Teledyne CZMIL Supernova. This sensor achieved bottom returns at depths down to 5 m in the south arm of GSL but only 0.5 m in the north arm. The CZMIL obtained bottom returns in freshwater Bear Lake at depths down to 20 m. Overall, both the pilot study and reconnaissance flights provided key insights for optimizing data collection and maximizing data quality of future surveys. Bathymetric lidar data collection for the entire shallow-water perimeter of GSL, including wetland areas of Farmington and Bear River Bays, will take place in mid-2025.