USGS presentation finds substantial lithium fluxes into Great Salt Lake, but key uncertainties remain

Scott Heenick, a hydrologist with the U.S. Geological Survey’s Utah Water Science Center, told the Great Salt Lake Tech Team that new sampling shows measurable lithium loads entering the lake and that conservative estimates indicate substantial annual fluxes.

Heenick presented about 700 new lithium concentration measurements from across the Great Salt Lake basin and said those data, paired with discharge measurements, yield a ‘‘mean load or flux of lithium [at Bear River, Corinne] is about 400 kilograms a day’’ — roughly 150 metric tons per year on an annualized basis. He described the estimate as conservative and dependent on choices about which parts of the hydrograph (baseflow versus runoff) to include.

Why it matters: lithium is concentrated in terminal basins such as Great Salt Lake, and new extraction technologies under study (including direct lithium extraction pilots) could change how much resource is removed or retained. Heenick emphasized large uncertainties in spatial sampling and temporal variability that complicate any simple ‘‘resource lifetime’’ calculation.

Heenick showed how mass load calculations combine concentration × volume × time, and he described a baseflow‑filter approach intended to give conservative, comparable values across watersheds. ‘‘If you take the Bear River at Corinne, we have 56 instances where we can multiply concentration times discharge,’’ Heenick said, reporting that a stricter baseflow filter reduced the sample set but gave a nearly identical mean and lower variance. He also described site‑level behavior that can change fluxes by orders of magnitude during runoff: at one Weber River site, baseflow fluxes were about 5 kilograms per day while spring‑runoff peaks exceeded 50 kilograms per day.

Heenick cautioned that the standing lithium resource in the lake and the rate at which it is replenished depend on many processes the team has not fully quantified, including interlake cycling, groundwater contributions, and ungaged springs. He noted work by colleagues that provides different estimates and that the team will refine numbers as more discharge and concentration values are verified. ‘‘That’s why I think we can keep stepping way below 2,700 [years] in terms of a time frame for this,’’ he said in reference to earlier, very large lifetime estimates, while adding that some estimates implied millennia and others hundreds of years depending on assumptions.

Several attendees pressed for more detail about point sources and springs. Heenick pointed to Crystal Hot Springs/Salt Creek and other high‑lithium springs as identifiable point sources in the Bear River reach; those sites show up as distinct clusters in concentration‑discharge plots. Participants also raised the possibility of pond leakage and aerosol transport as contributors or sinks. Heenick and others said available dust/aerosol measurements are limited and that legacy operations (e.g., historical magnesium extraction) have affected current lithium distributions.

Industry pilot and regulatory context: a representative of Waterleaf, a company conducting a small direct lithium extraction pilot, said the company ‘‘can extract lithium from the lake water and return the lake water, minus lithium’’ and confirmed willingness to present results to the tech team when the pilot’s feasibility assessment is complete. State staff noted that pilot operations must demonstrate water handling, ecosystem impacts and other criteria under existing review processes before larger production permits would be considered.

Data and next steps: Heenick said the ~700 basin samples will be integrated into a regional lithium database (the mineral resources program’s ~20,000‑entry regional dataset) and made available after verification of discharge values and concentrations. He and colleagues identified key follow‑up needs: better spatial coverage of ungaged springs, longer autosampler records at representative sites, more meteorological and groundwater data near specific shorelines, and refined estimates of dust/aerosol export.

The presentation concluded with agreement among members that the new data materially improve understanding but do not yet resolve the principal uncertainties about temporal peaks, point sources and how extraction methods might affect lake chemistry. The team plans to continue integrating data and invited pilot operators to return with verified results and chemistry at the pipe outlet.

The tech team’s conversation about lithium then shifted to the subsequent agenda item on research priorities and grant topics.