- New research traces human impacts on Great Salt Lake.
- Carbon and water cycles shifted after 19th-century settlement.
- A 1959 railroad causeway further altered the lake’s balance.
- Findings place modern changes in an 8,000-year context.
August 21, 2025 — A new study provides evidence that human activities have profoundly reshaped the Great Salt Lake’s chemistry and water balance over the past two centuries. Using sediment cores and isotope analysis, University of Utah researcher Gabriel Bowen
found that recent changes to the lake’s carbon and water budgets are unlike anything seen in the last 2,000 years, and unusual within the broader 8,000-year record.
The study looked at layers of lakebed mud rich in carbonate and organic material. These sediments act like a diary, recording shifts in carbon and oxygen isotopes that reveal how the lake’s hydroecology has changed through time. By comparing modern records with ancient ones, scientists can separate natural variation from human-driven disruption.
Settlement and Agriculture Leave Their Mark.
The first phase of change began in the mid-1800s, coinciding with colonial settlement of the Salt Lake Valley. As farmland spread and irrigation took hold, runoff carried more organic carbon into the lake. The isotopic record shows a marked decline in carbon values, pointing to new inputs from soil and agricultural activity.
This alteration of the carbon cycle was not mirrored by significant climate changes at the time, suggesting a direct link to human land use rather than natural variability.
Causeway Construction Shifts the Water Balance.
A second major shift occurred after 1959, when a railroad causeway was built across the lake. The barrier restricted water flow between the north and south arms, effectively changing the way the lake exchanged water and salt. Oxygen isotope values dropped, indicating that Gilbert Bay, the lake’s southern arm, began behaving less like a closed basin and more like an outlet system.
This structural change created different salinity levels in the lake’s divided arms. The south became fresher, while Gunnison Bay to the north grew saltier.
Lessons for Lake Management.
The findings suggest that the Great Salt Lake has already moved into ecological states not represented in thousands of years of natural history. For water managers, the sediment record provides both a warning and a potential tool. By showing what conditions were typical in the past, the data can help define safe management targets for the future.
Bowen notes that while the water balance might still be managed within historic ranges, the carbon cycle has entered a “no-analogue” state. This may affect nutrient loading, ecosystem health, and long-term stability of the lake’s biogeochemistry.
Broader Implications.
The study underscores the vulnerability of terminal saline lakes, which are among the most sensitive ecosystems on the continent. It also highlights how decisions made more than a century ago — from irrigation canals to railroad causeways — continue to shape the fate of the Great Salt Lake.
Citation.
Bowen, G. J. (2025). Multi-millennial context for post-colonial hydroecological change in Great Salt Lake. Geophysical Research Letters, 52, e2025GL116597. https://doi.org/10.1029/2025GL116597
