Matt Warner Reservoir is one of three lakes located in the Diamond Mountain area near Vernal, Utah. The reservoir, along with Calder and Crouse Reservoir, is a popular fishing spot in the northern Uintas.
Matt Warner experiences periodic harmful algal blooms, the most deadly one occurring in 2004, with a reoccurrence in 2010. Fifteen calves and three adult cows died from liver failure after drinking water from the reservoir during the 2004 toxic bloom. Sampling during this bloom showed the presence of Microcystis aeruginosa, a species of cyanobacteria that can produce microcystin, a powerful liver toxin.
The Division of Water Quality (DWQ) is monitoring the continued presence of elevated concentrations of cyanobacteria in Calder and Matt Warner reservoirs and has set the “decrease in dominance of blue-green algae” as a target for its total maximum daily load (TMDL) restoration plans for these reservoirs.
Update August 6, 2018
The Tri-County Health Department has issued an advisory for Matt Warner Reservoir based on toxin test results and bloom conditions. The Department of Natural Resources posted five warning signs around the reservoir on August 3, 2018.
Lab results from the Utah Department of Agriculture and Food (UDAF) lab confirmed the presence of anatoxin-a in a sample collected on July 26, 2018, on Matt Warner Reservoir. The previous test was inconclusive, but this latest test showed 0.14 micrograms per liter (µg/L) of anatoxin-a. This level exceeds the recreational health-based threshold.
Warning Advisory for Matt Warner Reservoir
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. Advisory actions:
- Do not swim or water ski
- Do not ingest the water
- Keep pets and livestock away
- Clean fish well and discard guts
- Avoid areas of scum when boating
Drone taking water column sample at Matt Warner Reservoir. July 31, 2018.
Update July 31, 2018
The Division of Water Quality (DWQ) visited the reservoir on July 26, 2018. The monitoring crew observed a thick bloom that extended from the shore near the main boat ramp into the open water. The bloom was thick throughout the water column, and in some areas consolidated at the surface. Rapid test strip results from samples collected in the area were inconclusive for microcystin and non-detect for anatoxin.
The crew boated into the open water, where they observed that the bloom extended continuously across the water. Rapid test strip results from the open water sample showed approximately 10 micrograms per liter (µg/L) of microcystin and inconclusive results for anatoxin-a. Microcystin levels exceeded recreational health-based thresholds.
The samples were delivered to the Utah Public Health Lab and the Utah Department of Agriculture and Food (UDAF) lab for further analysis. Ranchers in the area have been alerted about the toxin levels at the reservoir so they can keep their cattle away from the water.