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Great Salt Lake advisers: elevations steady, salt mass shrinking but forecasts vary by climate scenario
Summary
Advisory council staff reported modest recent rises in South- and North-Arm elevations, seasonal discharge variability and a consistent salt export to the North Arm; staff presented scenario-based forecasts that range widely by wet/cool vs. warm/dry conditions and highlighted monitoring gaps.
Advisory committee staff reported updated measurements of water-surface elevation, streamflow and salinity at the Great Salt Lake and outlined seasonal forecasts for 2025.
The Utah Geological Survey presentation said the South Arm gauge daily value was about 41.926 feet on the most recent reading and the North Arm about 41.918 feet, producing a measured head difference of roughly 0.6 foot. Staff noted that while some inflow stations show cumulative streamflow near or below median values for the water year, others—such as a Farmington Bay site—are recording exceptionally high cumulative flows for this time of year.
"We're seeing about a 0.5 foot rise since the seasonal low in November," said Andrew Ropke, summarizing recent elevation trends and noting the north/south differences at long-term gauges.
Why it matters: Christine Ramsey (Utah Geological Survey) presented a salt-mass analysis showing the South Arm has lost substantial salt mass to the North Arm since mid-2023. Her linear fit to available data produced an estimated export on the order of hundreds of thousands of tons per day during export peaks; she described an average-scale removal that the modeling expresses as roughly 400,000 tons per day during the most active export period, and she said independent flux measurements at the breach are consistent with the lake-sample–based mass estimates.
Ramsey emphasized uncertainty in forecasts: "We have to make some educated guesses for what is coming back in," she said, noting that predictions assume differing climate scenarios. Under the committee's set of scenarios—average, wet/cool and warm/dry—projected South Arm salinity for late June ranged from roughly 105 g/L in a dilution/wet scenario to higher values in warm/dry simulations. October projections similarly span a range with salinity outcomes sensitive to how much north→south flow reestablishes. Ramsey cautioned that precise numerical forecasts depend on better continuous monitoring and on model updates to reflect the current berm and breach configuration.
Monitoring gaps and equipment loss: Staff reported efforts to expand streamflow gauge coverage under interagency agreements (14 gauges were planned; seven installed to date) and said permitting and shallow-water conditions complicate installations. The group also reported the loss of one lake-elevation station after a piling failure in August; staff estimated the equipment loss at about $10,000 and said reestablishing the site could cost $50,000–$100,000 if a new piling must be driven.
Next steps: Committee members asked for more frequent salinity profiles at the breach and improved velocity/flux data so modelers can better quantify how much north→south flow would be required to hold salt mass near the committee’s 'happy-place' range. Ramsey said the group will continue scenario work and recommended additional monitoring to constrain forecasts.
