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County surveyors use hydro‑drone to update Settlement Canyon reservoir capacity, find ~3% loss since 1990s
Summary
Tooele County surveyors presented a drone-based bathymetry survey of Settlement Canyon Reservoir that produced a new volume model and an estimated 3% capacity loss since Army Corps estimates in the 1990s; staff said rapid re-surveys will help plan dredging and emergency response.
Tooele County surveyor staff demonstrated a new drone‑based bathymetry survey that produced an updated model of Settlement Canyon Reservoir and an estimate of modest capacity loss compared with older Army Corps of Engineers figures.
Recorder‑Surveyor Jerry Helton introduced the presentation and said the drone work will allow county staff and irrigation companies to monitor reservoir capacity much more frequently and accurately than the decades‑old estimates. Senior field surveyor Hayden Langston showed an AutoCAD surface compiled from sonar and survey‑grade GPS data and said the new method lets staff calculate reservoir volume quickly after a site visit.
"Since the Army Corps of Engineers estimation in the nineties, we've lost 3 percent capacity since then," Langston said, characterizing the change as expected but important to track. Helton added that modern, repeatable surveys will help the county spot faster changes after storms or siltation events and support planning for dredging if needed.
Langston explained the workflow: the hydro‑drone carries a rover and sonar, records surface elevation and bottom depth, and produces a 3‑D model that staff can convert to volume estimates. He said re‑surveying can be completed and analyzed within roughly a day, giving emergency planners and irrigation companies near real‑time data about how much water is available.
Council members asked technical questions about how silt depth varies through the reservoir and under what thresholds dredging would be triggered. Langston said precise sediment thickness depends on location within the reservoir and would require localized analysis; Helton summarized historical capacity estimates (1965 estimates, Army Corps follow‑up in the 1980s–90s) and said the county now has a baseline figure (reported as 960.43136 acre‑feet in the presentation) that staff can compare with future surveys.
The survey team said they will share raw data with local water users and integrate results into the county GIS to support fire‑fighting, planning and periodic monitoring. Council members praised the pilot and asked staff to schedule additional reservoir surveys over the coming months.
What happens next: staff will continue hydro‑drone surveys and prepare a recommended schedule for other county reservoirs; any dredging or capital repairs would be evaluated and scoped once follow‑up measurements determine the rate of capacity loss.
