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Rockport Reservoir Algal Bloom 2017

| Updates | Data |

Rockport Reservoir, sometimes known as Wanship Reservoir, is about three miles long and one-half mile wide and covers more than 500 acres. The state park is a popular recreation site for boating, fishing and water sports. The 6,000-foot-elevation reservoir was created by the Wanship Dam in the 1950’s.

Update November 1, 2017

The Summit County Health Department (SCHD) sampled Rockport Reservoir on October 31, 2017. Toxin test strips results for the samples were all below the UDEQ-UDOH action level for mycrocystins, cylindrospermopsin, and anatoxin-a. Based on these findings, SCHD lifted the “Warning Advisory” for Rockport Reservoir on November 1, 2017, and removed the warning signs.


Update October 26, 2017

Samples testing positive for cyanotoxins from samples collected on October 17, 2017 and October 19, 2017, were sent to the Utah Public Health Lab for ELISA testing to quantify the strip-test results. ELISA test results showed microcystin levels above the UDOH-UDEQ recommended health-advisory threshold for a warning advisory for the October 17, 2017, samples. However, ELISA test results for the October 19, 2017, sample were below the UDOH-UDEQ recommended health-advisory threshold. These variations demonstrate how quickly toxin concentrations can change.

Cyanobacteria cell counts were 195,000 cells per milliliter (cell/ml), greatly above the UDOH-UDEQ recreational warning-advisory threshold. Multiple cyanobacteria taxa capable of producing toxins were present, including Dolichospermum and Pseuadanabaena, but the sample was dominated by Aphanizomenon at 192,933 cells/ml. Aphanizomenon and Dolichospermum are potential toxin producers for microcystin, anatoxin-a, and cylindrospermopsin. Pseuadanabaena is a potential toxin producer for microcystin and anatoxin-a.

The warning advisory at Rockport Reservoir remains in effect.

Warning Advisory for Rockport Reservoir

A Warning Advisory indicates a moderate relative probability of acute health risk, cell count density of 20,000 -10 million cells per milliliter, 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 drink the water
  • Keep pets and livestock away
  • Clean fish well and discard guts
  • Avoid areas of scum when boating

Toxins

ELISA testing by the Utah Public Health Lab reflected changes in microcystin levels at sample locations over the course of a few days.

October 17, 2017

  • Western Beach: 7.6 micrograms per liter (µg/L) of microcystin
  • Marina: 8.7 µg/L of microcystin

October 19, 2017

  • Western Beach: 0.13 µg/L of microcystin

Update October 18, 2017

During an E. coli monitoring expedition at recreational areas on October 17, 2017, Division of Water Quality (DWQ) field staff observed what appeared to be a cyanobacteria bloom on Rockport Reservoir at the marina and western beach areas. DWQ collected three samples at these two locations on the reservoir. Toxin strip-test results showed microcystin and anatoxin-a levels above the UDEQ-UDOH recommended health-advisory thresholds for a warning advisory for recreational waters. The blooms appear to be localized and do not compromise drinking water.

Samples testing positive for cyanotoxins were sent to the Utah Public Health Lab and Utah Department of Agriculture and Food for ELISA testing to quantify the strip-test results. Lab results should be available before the end of this week or early next week. DWQ is working with the Summit County Health Department to resample the reservoir on Thursday, October 19, 2017.

Warning Advisory for Rockport Reservoir

A Warning Advisory indicates a moderate relative probability of acute health risk, cell count density of 20,000 -10 million cells per milliliter, 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 drink the water
  • Keep pets and livestock away
  • Clean fish well and discard guts
  • Avoid areas of scum when boating

Toxin Test Strip Results

DWQ collected three samples on the reservoir. Toxin strip-tests showed the following:

  • Western Beach: 5 micrograms per liter (µ/L) for microcystin; non-detect for anatoxin-a and cylindrospermopsin
  • Marina: 0.4 µ/L for anatoxin-a; non-detect for microcystin and cylindrospermopsin;
  • Marina (surface scum): non-detect for cylindrospermopsin, and anatoxin-a

Rockport Marina Beach Boat Storage

Rockport Marina

Rockport Western Beach

Rockport Western Beach


Update August 22, 2017

Division of Water Quality (DWQ) scientists observed an algal bloom on the reservoir on August 15, 2017. The bloom appeared to cover 25-35 percent of the reservoir, was concentrated at the western beach, and was present at the beach area near the marina. Characteristic algal-bloom streaks were observed lake-wide. DWQ staff collected water samples and conducted toxin strips tests. The toxin strip tests came back non-detect for anatoxin-a, microcystin, and cylindrospermopsin.

The Summit County Health Department and DEQ’s Division of Drinking Water have been notified about the bloom.

Sampling Date, Locations, and Cyanobacteria Cell-Count Concentrations

August 15, 2017

DWQ scientists collected four samples across the reservoir. The dominant cyanobacteria genus found in the samples was Aphanothece, which the literature suggests is not a cyanotoxin producer. Cell-count densities were considerably lower above the reservoir than within the reservoir.

  • Rockport Reservoir at marina: 34,467 cells/milliliter (cells/ml)
  • Rockport Reservoir at west side beach: 23,273 cells/ml
  • Weber River above Rockport Reservoir: 2,109 cells/ml
  • Smith and Morehouse Reservoir at boat ramp: 34,510 cells/ml

Toxins

Strip tests came back non-detect for anatoxin-a, microcystin, and cylindrospermopsin.