Deer Creek Reservoir Algal Bloom Monitoring 2019

Warning Advisory
Harmful Algae Present
in Some Areas of Waterbody

  • Do not swim or water ski in areas of algae scum
  • Avoid areas of algae scum when boating.
  • Keep animals away.
  • Do not ingest the water.
  • Clean fish well and discard guts.

Report a Bloom

24-Hour DEQ Environment Incidents Line: (801) 536-4123

Call Utah Poison Control Center

If you believe you or your pet have been exposed to a harmful algal bloom, call (800) 222-1222.

Get BloomWatch App

Help us track cyanobacteria blooms with your smartphone. Go to cyanos.org for more info.

Update August 30, 2019

Deer Creek Reservoir, North End of Reservoir (Looking East to West), Drone footage, Week of August 26, 2019.

Deer Creek Reservoir, North End of Reservoir (Looking East to West), Drone footage, Week of August 26, 2019.


The Wasatch County Health Department (WCHD) posted Warning Advisory signs at access points on Deer Creek Reservoir on August 30, 2019, to alert the public about areas of the reservoir that are experiencing harmful algal blooms.

Deer Creek Reservoir remains open for recreation at this time. Recreationists are advised to not swim or waterski in areas of scum, avoid boating in areas of scum, keep animals away, and not ingest water. Visitors can still recreate in the reservoir but are cautioned to be mindful of water conditions, as blooms may move or disperse depending on temperature, wind, and weather.

The Division of Water Quality (DWQ) and WCHD visited the reservoir multiple times between August 26 and August 29, 2019, and observed cyanobacteria accumulations at the Charleston Day Use area and the northern portion of the reservoir. Cyanobacteria were also observed at other areas of the reservoir. Satellite imagery and drone footage confirm the extent of the bloom.

DWQ and WCHD collected samples at a variety of locations on the reservoir on August 29, 2019. These samples have been submitted to the lab, and results should be available early next week.

Test results received on August 28, 2019, for samples collected on August 27, 2019, at the Charleston Day Use Area showed cyanobacteria cell-count concentrations of approximately 728,000 cells per milliliter (cells/mL), which exceeds the recreation health-based threshold for a Warning Advisory. The primary taxon in the samples was Dolichospermum, a species that can produce both microcystin and anatoxin-a. Toxin test results received to date, however, were well below the health advisory threshold.

A Warning Advisory indicates a moderate relative probability of acute health risk, cell-count density of 20,000 – 10 million cells per milliliter (cells/ml), microcystin levels of 4-2,000 micrograms per liter (µg/L), or anatoxin-a levels above non-detect.

Data Summary

Surface Sample

  • Sample date: August 27, 2019
  • Microcystin: 0.24 micrograms per liter (µg/)
  • Anatoxin-a: <0.10 µg/L
  • Cell counts: 727,167 cells per milliliter (cells/mL)

Elbow-depth Integrated Composite Sample

  • Sample date: August 27, 2019
  • Microcystin: <0.10 micrograms per liter (µg/)
  • Anatoxin-a: <0.10 µg/L