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Great Salt Lake rises; salinity falls to ~111 g/L with forecasts pointing to modest autumn recovery
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Summary
Agency scientists reported June biannual salinity samples showing open-water values near 111 grams per liter and presented fall forecasts that range roughly 115–118 g/L depending on evaporation scenarios; the shift stems partly from export of salt mass through the causeway breach and raises questions about targeting salt mass versus concentration in management.
Scientists monitoring the Great Salt Lake told the Utah Great Salt Lake Advisory Council that water levels have climbed back to values seen several years ago while salinity across sampled sites has declined to about 111 grams per liter.
"We're sitting below 120 grams per liter," said Christine Ramsey (role not specified), summarizing June samples collected June 5–13 under the council’s biannual monitoring agreement. Ramsey reported June point measurements of 111 g/L at a Gilbert Bay site and 110 g/L at Carrington. She said shallow sampling at the new breach returned about 109 g/L, Lakeside measured 111 g/L, and Saltair registered 103 g/L.
The report framed those readings with a volume-weighted-average salinity of about 111 g/L in the South Arm for June. Using that starting point and three climate/inflow scenarios, Ramsey provided fall forecasts ranging roughly from 115 to 118 g/L, depending principally on evaporation assumptions and how much salt continues to be exported through the causeway breach.
The advisory council discussion focused on salt mass — the total mass of dissolved salt in the lake — as an alternate management target to concentration. Ramsey and others showed isomass plots (lines of equal salt mass) to illustrate how salinity and volume interact. Ramsey said her mass-calculation work suggests the lake’s standing salt mass fell from about 1.1 billion tons in mid‑2023 and has continued to decline toward a lower isomass (presented as between ~900 million and 1,000 million tons in the meeting discussion).
Committee members and agency scientists agreed that the breach has exported a substantial amount of salt northward and that historic discharge measurements through the old culverts are uncertain. As Bill Johnson (committee member) put it, shifting to net export is the primary lever the agencies can use to change which isomass line the system occupies.
The group also noted ecological thresholds. Participants discussed brine-shrimp and brine-fly concerns if salinity fell far below current levels; speakers referenced literature and historical monitoring that indicate population responses occur in the 90–100 g/L band and below in some cases.
Next steps identified by the council include integrating the isomass framework into a salinity-management plan, running scenario brackets (average/low/high inflow years), and refining monitoring of key flows and salt exports to reduce uncertainty in forecasts. The council asked members to review analytic outputs and to feed scenario requests back to staff ahead of planned CMP and salinity-plan work.
