HAB warning advisory issued for Scofield Reservoir

July 26, 2018 GMT

SALT LAKE CITY — Southeast Health Department has issued a Harmful Algal Bloom (HAB) Warning Advisory for Scofield Reservoir after Division of Water Quality (DWQ) samples showed that cyanobacteria cell counts and anatoxin-a levels exceeded health-based thresholds. The Madsen Bay Boat Ramp, Mountain View Boat Ramp, and Frandsen Boy Scout Camp currently show the heaviest bloom activity.

Warning 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.


Advisory actions

Advisory actions for Scofield Reservoir include the following:

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.

For more information and updates on bloom conditions at Scofield Reservoir, visit habs.utah.gov.


A DWQ monitoring crew observed increased bloom activity during July 5, sampling at the reservoir. Toxin test-strip results and subsequent Utah Public Health Lab (UPHL) testing came back non-detect for microcystin, but test strips and UPHL tests were both positive for anatoxin-a.

Cyanobacteria cell-count concentrations were well above health-based thresholds, with cell densities of more 3.4 million cells per milliliter (cells/ml) at the Madsen Bay Boat Ramp and greater than 250,000 cells/ml at the Mountain View Boat ramp.

All cyanobacteria found in the samples were identified as Dolichospermum, a toxin-producing genus of cyanobacteria.

The monitoring crew returned to Scofield Reservoir to collect additional samples on July 10 and 12. DWQ scientists, the DEQ District Engineer, and Southeast Health Department officials observed additional bloom activity at the Boy Scout Camp and the upstream inlet of Madsen Bay.

Based on cyanobacteria cell-count concentrations, the detection of anatoxin-a at sampling sites, and visual observations, the Southeast Health Department issued a Warning Advisory for Scofield Reservoir.

According to the Southeast Utah Health Department, city drinking water and Price River Water Improvement District (PRWID)-supplied water is treated and is safe to drink. Canal water is currently unaffected by any residual bloom.

While some areas of Scofield Reservoir are not currently affected by visible blooms, algae may move or disperse depending on temperature, wind, and weather. Recreationists are advised to be mindful of conditions, as they may change over the course of the day.