Get Full Government Meeting Transcripts, Videos, & Alerts Forever!
Get email alerts on the Hydrology Monitoring topic
No spam. Unsubscribe anytime.
USGS reports changing flows, bidirectional causeway velocities and lab testing plans for lake nutrients
Summary
USGS scientists said changing lake elevations and winds have produced bidirectional flows through the causeway and curtailed continuous discharge estimates at key monitoring sites; the agency is testing alternative labs and methods for nutrient analyses in hypersaline Great Salt Lake samples.
Christine Ramsey of the U.S. Geological Survey (USGS) updated the group on hydrology, velocities in the causeway reach, inflow totals and ongoing work to secure analytical capacity for nutrient samples from hypersaline Great Salt Lake sites.
Ramsey summarized lake elevations: the overall lake elevation had dropped roughly three feet from spring highs at the time of the meeting and the North Arm was down about seven feet relative to its seasonal high. She briefed monitoring changes at a long‑running causeway reach where acoustic velocity profiles now show frequent reversals and north‑to‑south flow events at depth that began in late August 2024. “With these changing conditions … we can no longer do that,” Ramsey said, referring to continuous, stage‑discharge relationships the group previously used to produce a continuous discharge record at that site; the existing continuous discharge record ended in August 2023 because bidirectional flow broke the stage‑discharge assumption.
USGS staff reported monthly discrete discharge measurements will continue, and the agency is exploring a new method using multi‑cell velocity profiles and pressure transducers to reconstruct continuous discharge. Ramsey also described localized evidence of north‑to‑south flow through the western breach and noted a south‑arm sample taken November 20 showed north‑to‑south flow about 10 feet below the surface during calm conditions.
On inflows, Ramsey said cumulative seasonal flows at Bear River, Weber and Farmington remain near or below median values for the water year to date; total cumulative numbers are well below the prior water year totals. She described outflow monitoring complexities at the river mouth (Corinne) and plans to instrument that cross section with a side‑looking acoustic Doppler and pressure transducers to improve estimates.
Ramsey and colleagues also described lab testing and nutrient analysis challenges after an analytical partner had been unreliable earlier in 2024. USGS is running an inter‑lab comparison this winter: split samples were sent to Chesapeake Biological Laboratory and NWQL (National Water Quality Laboratory) and additional samples will be split to High Sierra and other candidate labs for ammonia, dissolved nitrogen and orthophosphate methods. Ramsey said NWQL plans to acquire an instrument to better handle ammonia in high‑salinity matrices, but that capability likely will come online in 2025; in the interim USGS is testing multiple labs and dilution/spike approaches to determine a cost‑effective, reliable analytical pathway.
Why it matters: Accurate long‑term discharge and nutrient records are central to interpreting salinity, algal and food‑web dynamics at Great Salt Lake. Changing hydraulics through the causeway and instrument/method limitations for hypersaline nutrients complicate continuous monitoring and trend analysis.
Sources and attributions: Quotes and technical descriptions in this item are taken from Christine Ramsey (USGS) and the USGS presentation at the meeting.
