Matt Warner Reservoir Algal Bloom Monitoring 2019

Warning Advisory

  • Do not swim or water ski in this area.
  • 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.


Visit the 2019 Photo Gallery

Get BloomWatch App

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

Update October 2, 2019

Matt Warner, September 19, 2019

The Tri-county Health Department (TCHD) downgraded Matt Warner Reservoir from a Danger Advisory to a Warning Advisory on October 2, 2019, after two consecutive weeks of lab results showed that cyanobacteria cell-count and cyanotoxin concentrations had dropped below the recreation health-based threshold for a Danger Advisory.

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

Boat Ramp

  • Sample date: September 19, 2019
  • Sample type: Elbow-depth composite sample
  • Microcystin: 2.0 micrograms per liter (µg/L)
  • Anatoxin-a: 0.163 µg/L
  • Cyanobacteria cell counts: Pending

Update September 25, 2019

Matt Warner, September 5, 2019

Toxin test results for samples collected by the Division of Water Quality (DWQ) at the boat ramp on Matt Warner Reservoir on September 19, 2019, exceeded the recreation health-based threshold for a Warning Advisory for anatoxin-a. Toxin test results for samples collected at the boat ramp on Matt Warner Reservoir on September 5, 2019, however, were well below the recreation health-based threshold for a Warning Advisory. Cyanobacteria cell-count concentration results for both sample dates are pending from PhycoTech.

The DWQ monitoring crew observed bright green cyanobacteria in the water column that resembled grass clippings. The water was clear. The crew reported that conditions were much improved from previous visits.

A Danger Advisory indicates a high relative probability of acute health risk, cell-count density of >10 million cells per milliliter (cells/mL), microcystin levels >2,000 micrograms per liter (µg/L), or anatoxin-a levels >90 µg/L.

Matt Warner Reservoir remains under a Danger Advisory pending cyanobacteria cell-count data from PhycoTech.

Data Summary

Boat Ramp

  • Sample date: September 5, 2019
  • Sample type: Elbow-depth composite sample
  • Microcystin: <2.0 micrograms per liter (µg/L)
  • Anatoxin-a: <0.10 µg/L
  • Cyanobacteria cell counts: Unavailable

Boat Ramp

  • Sample date: September 19, 2019
  • Sample type: Elbow-depth composite sample
  • Microcystin: 2.0 micrograms per liter (µg/L)
  • Anatoxin-a: 0.163 µg/L
  • Cyanobacteria cell counts: Unavailable

Update September 5, 2019

Cyanobacteria cell-count results received by the Division of Water Quality (DWQ) on September 4, 2019, for samples collected at the West Boat Ramp at Matt Warner Reservoir on August 23, 2019, exceeded the recreation health-based threshold for a Warning Advisory. Cyanobacteria cell-count concentrations in the surface sample were at the higher end of the advisory threshold at approximately 1.6 million cells per milliliter (mL). The primary taxon in the samples was Aphanizomenon, but Dolichospermum and Microcystis were found in the water-column sample.

Toxin test results for anatoxin-a and microcystin were non-detect with exception of microcystin in the surface sample. DWQ is now running new dilution curves for its enzyme-linked immunosorbent assay (ELISA) analysis for cyanotoxins. These different dilution ratios (1:1000 and 1:20) have changed the detection limit for microcystin from <0.10 micrograms per liter (µg/L) to <2.0 µg/L. The 1:20 dilution will detect toxin levels between 2 and 100 µg/L, and the 1:1000 dilution will detect toxin levels between 100 and 5,000 µg/L. These new dilution ratios should result in faster lab results. If further precision is needed, the lab will run additional dilutions.

The DWQ monitoring crew observed a visible cyanobacteria bloom that resembled grass clippings during their August 23, 2019, site visit. The cyanobacteria appeared to be attaching themselves to the lake vegetation, and the wind had pushed the cyanobacteria up against the lakeshore.

A Danger Advisory indicates a high relative probability of acute health risk, cell-count density of >10 million cells per milliliter (cells/mL), microcystin levels >2,000 micrograms per liter (µg/L), or anatoxin-a levels >90 µg/L. Matt Warner Reservoir can be downgraded to a Warning Advisory if the next sample falls below the recreation health-based threshold for a Danger Advisory.

Matt Warner Reservoir remains under a Danger Advisory.

Data Summary

Surface sample

  • Sample date: August 23, 2019
  • Microcystin: 2.9 micrograms per liter (µg/L)
  • Anatoxin-a: <0.10 µg/L
  • Cyanobacteria cell counts: 1,662,646 cells per milliliter (cells/mL)

Elbow-depth integrated composite sample

  • Sample date: August 23, 2019
  • Microcystin: < 2.0 micrograms per liter (µg/L)
  • Anatoxin-a: <0.10 µg/L
  • Cyanobacteria cell counts: 19,084 cells per milliliter (cells/mL)

Update August 14, 2019

Matt Warner Reservoir, August 6, 2019

The Tri-County Health Department (TCHD) issued a Danger Advisory on August 12, 2019, for Matt Warner Reservoir and closed the waterbody after cyanobacteria cell-count concentrations from samples collected at the boat ramp on August 6, 2019, were nearly 11 times greater than the recreation health-based threshold for a Danger Advisory. Aphanizomenon was the primary taxon in all samples.

TCHD posted Danger signs warning the public against fishing, swimming, or recreating in the reservoir during the closure. The Division of Wildlife Resources (DWR) made the decision to close the waterbody to fishing from Aug. 13, 2019, to Sept. 30, 2019, after consulting with health officials.

DWR Director Mike Fowlks issued an emergency amendment to the 2019 Utah Fishing Guidebook to address the fishing closure on Matt Warner Reservoir. The amendment makes it illegal for anyone to fish at the reservoir during the dates specified, and anyone found fishing at Matt Warner during that time could be cited.

Hunting and camping in the Diamond Mountain Wildlife Management Area will still be allowed. However, campers and hunters with dogs should avoid the area unless they can ensure that their pets will not get in the water.

Toxin test results show microcystin levels of 9.5 and 4.3 micrograms per liter (µg/L), and anatoxin-a was detected in both samples. These values were above the recreation health-based threshold for a Warning Advisory.

A Danger Advisory indicates a high relative probability of acute health risk, cell-count density of >10 million cells per milliliter (cells/mL), microcystin levels >2,000 micrograms per liter (µg/L), or anatoxin-a levels >90 µg/L.

Data Summary

Main Boat Ramp

Sample Type: Surface sample
Sample Date: August 6, 2019
Microcystin: 9.5 micrograms per liter (µg/L)
Anatoxin-a: 0.107 µg/L
Cell Counts: 109,546,842 cells per milliliter (cells/mL)

Main Boat Ramp

Sample Type: Elbow-depth integrated composite sample
Sample Date: August 6, 2019
Microcystin: 4.3 micrograms per liter (µg/L)
Anatoxin-a: 0.145 µg/L
Cell Counts: 1,833,214 cells per milliliter (cells/mL)


Update August 5, 2019

Matt Warner Reservoir, July 29, 2019

Matt Warner Reservoir, July 30, 2019

The Division of Water Quality (DWQ) has received toxin test results and cyanobacteria cell-count densities from samples collected on July 30, 2019, at the Main Boat Ramp of Matt Warner Reservoir.

Toxin test-results show a decrease in microcystin and a slight increase in anatoxin-a from non-detect to detect. Cell counts continue to drop but remain at the upper level of the recreation health-based threshold for a Warning Advisory. Aphanizomenon was the primary taxon in the samples at the Boat Ramp.

A Warning Advisory indicates a moderate relative probability of acute health risk, a 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.

The Warning Advisory remains in place for Matt Warner Reservoir.

Main Boat Ramp

  • Sample Type: elbow-depth integrated composite sample
  • Sample Date: July 30, 2019
  • Microcystin: 0.38 micrograms per liter (µg/L)
  • Anatoxin-a: 0.108 µg/L
  • Cell Counts: 370,940 cells per milliliter (cells/mL)

Main Boat Ramp

  • Sample Type: surface sample
  • Sample Date: July 30, 2019
  • Microcystin: 3.5 micrograms per liter (µg/L)
  • Anatoxin-a: 0.148 µg/L
  • Cell Counts: 2,340,026 cells per milliliter (cells/mL)

Update July 30, 2019

Matt Warner Reservoir, July 11, 2019

The Division of Water Quality (DWQ) has received toxin test results and cyanobacteria cell-count densities from samples collected on July 22, 2019, at the North Shore and Main Boat Ramp of Matt Warner Reservoir.

Cyanobacteria cell-count concentrations at the North Shore dropped from approximately 9.4 million cells per milliliter (mL) in the July 11, 2019, sample to approximately 3.6 million cells/mL. There was a similar decrease in cell-count densities at the Main Boat Ramp. Cell counts continue to be on the upper level of the recreation health-based threshold for a Warning Advisory.

Dolichospermum, a taxon that produces both microcystin and anatoxin-a, made up the majority of the sample at the North Shore. However, Aphanizomenon, another microcystin-producing taxon, was also present at high levels at the North Shore. Aphanizomenon was the primary taxon at the Boat Ramp.

Toxin test results show while cell-count densities have dropped at the North Shore, microcystin levels have increased and now exceed the recreation health-based threshold for a Warning Advisory. Further dilutions by the Utah Public Health Lab (UPHL) are needed to quantify microcystin concentrations at the North Shore. Cyanobacteria cell die-off may be responsible for the increase in the toxin levels since cyanobacteria often release toxins during cell death (lysis).

Toxin Test Results

  • North Shore: Between 5 and 120 micrograms per liter (μg/L) of microcystin (further dilutions required)
  • Main Boat Ramp: 1.1 μg/L of microcystin

Cyanobacteria Cell-Count Concentrations

  • North Shore: 3,566,228 cells per milliliter (cells/mL)
  • Main Boat Ramp: 515,972 cells/mL

The Warning Advisory for Matt Warner Reservoir remains in place.


Update July 19, 2019

The Division of Water Quality (DWQ) received cyanobacteria cell-count concentration results on July 16, 2019, from both surface and an elbow-depth integrated composite samples collected at the Matt Warner Reservoir Boat Ramp on July 11, 2019. PhycoTech reported that there were approximately 9.4 million cells per milliliter (cells/mL) in the surface sample and 1.3 million cells per milliliter (cells/mL) in the depth-integrated sample. The predominant species continues to be Dolichspermum, a cyanobacteria taxon that can produce both microcystin and anatoxin-a. The cyanobacteria cell count of 9.4 million cells/mL is close to the recreation health-based threshold of 10 million cells/mL for a Danger Advisory, in which the lake would be closed.

Toxin test results from the Utah Public Health Lab (UPHL) show <0.10 micrograms per liter (μg/L) of anatoxin-a and 2.79 μg/L of microcystin for the surface sample. Toxin levels of microcystin are near the recreation health-based advisory threshold for a toxin-based Warning Advisory.

The Warning Advisory remains in place at Matt Warner Reservoir.


Update July 5, 2019

The Division of Water Quality (DWQ) received cyanobacteria cell-count concentration results on July 5, 2019, from an elbow-depth integrated composite sample collected at the Matt Warner Reservoir Boat Ramp on July 2, 2019. PhycoTech reported that there were approximately 1.8 million cells per milliliter (cells/mL) in the sample. The predominant species was Dolichspermum, a cyanobacteria taxon that can produce both microcystin and anatoxin-a.

While initial toxin tests came back well below the advisory threshold, the cyanobacteria cell-count density of 1,788,578 cells/mL falls at the upper end of the recreation health-based advisory threshold for a Warning Advisory.

The Warning Advisory remains in place at Matt Warner Reservoir.


Update July 3, 2019

Matt Warner Reservoir, July 2, 2019

The Tri-County Health Department issued a Warning Advisory for Matt Warner Reservoir today after a monitoring crew from the Division of Water Quality (DWQ) observed bloom material at a number of sites at the reservoir.

DWQ collected samples at Matt Warner Reservoir on July 2, 2019. The monitoring crew noticed visible lime-green clumps dispersed throughout the water column, with higher concentrations of cyanobacteria in aquatic plants along the shore and on the shoreline. Potential bloom material was observed at all sites visited at the reservoir.

Scientists took surface and elbow-depth integrated composite samples at the boat ramp. Toxin test results from the Utah Public Health Lab (UPHL) on July 3, 2019, showed the samples were below the recreation health-based thresholds for an advisory.

  • Matt Warner Boat Ramp (surface sample): <0.10 micrograms per liter (µg/L) of anatoxin-a; 0.63 µg/L of microcystin
  • Matt Warner Boat Ramp (elbow-depth integrated composite sample): <0.10 µg/L of anatoxin-a; 0.14 µg/ of microcystin

While the sample results were below advisory thresholds, the presence of a visible bloom can serve as cause for the issuance of an advisory, since toxin levels can vary from day to day.

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.