Herington Reservoir algae bloom history
The Kansas Department of Health and Environment has tested Herington Reservoir 9 times since 2012, usually after someone reported a possible bloom. 2 samples (22%) reached at least Watch level, and 1 reached Warning level or higher.
- 2012 6 samples, Watch
- 2013 None
- 2014 None
- 2015 None
- 2016 None
- 2017 None
- 2018 None
- 2019 None
- 2020 None
- 2021 2 samples, Warning
- 2022 1 sample
When do algae blooms happen at Herington Reservoir?
About 100% of reports fall between May and September, when warm, calm, sunny weather lets blue-green algae multiply.
Blooms can appear, move with the wind and fade within hours or days, so the time of year is only a guide.
Recent Herington Reservoir algae reports
| Date | Location | Result |
|---|---|---|
| 6 June 2022 | Herington Reservoir South Ramp | Below advisory levels · microcystin 0.17 µg/L, 68,457 cyanobacteria cells/mL |
| 19 July 2021 | Herington Reservoir South Ramp | Below advisory levels · microcystin not detected, 6,950 cyanobacteria cells/mL |
| 21 June 2021 | Herington Reservoir South Ramp | Warning level · microcystin 2.89 µg/L, 317,561 cyanobacteria cells/mL |
| 23 July 2012 | Herington Reservoir South Ramp | Below advisory levels · microcystin not detected, 6,104 cyanobacteria cells/mL |
| 23 July 2012 | Herington Reservoir South Ramp | Below advisory levels · microcystin not detected, 16,179 cyanobacteria cells/mL |
| 16 July 2012 | Herington Reservoir South Ramp | Below advisory levels · microcystin not detected, 54,815 cyanobacteria cells/mL |
| 16 July 2012 | Herington Reservoir South Ramp | Below advisory levels · microcystin not detected, 31,202 cyanobacteria cells/mL |
| 11 July 2012 | Herington Reservoir South Ramp | Below advisory levels · microcystin 3 µg/L, 66,146 cyanobacteria cells/mL |
| 11 July 2012 | Herington Reservoir South Ramp | Watch level · microcystin 5 µg/L, 119,098 cyanobacteria cells/mL |
What the Kansas results mean
KDHE sets each advisory from lab results or what staff see at the lake. Samples on this page are labelled with the level their results reached.
- Watch
- A bloom is visible, microcystin is above 4 µg/L, or there are more than 80,000 cyanobacteria cells per mL. Avoid algae and keep people and pets from swimming near it or drinking the water.
- Warning
- Microcystin above 8 µg/L, more than 250,000 cells per mL, or heavy surface scum. Avoid all contact with the water, including fishing and boating.
- Hazard
- Microcystin above 2,000 µg/L or more than 10 million cells per mL. KDHE recommends closing all or part of the lake and sometimes the shore nearby.
Is Herington Reservoir safe for dogs?
Dogs are at the greatest risk from toxic algae. They swallow water while swimming, eat scum on the shore and lick algae off their fur afterwards, and a small amount can kill a dog within hours.
- Keep your dog on a lead near water that looks green, scummy, foamy or discoloured, and away from algae washed up on the shore.
- If your dog gets in, rinse it straight away with clean water and don't let it lick its coat.
- Call a vet immediately if your dog vomits, drools, has diarrhoea, staggers, shakes or seems weak after being near the water.
Read the full guide to toxic algae and dogs: symptoms, what to do in the first minutes and how vets treat it.
Health effects of toxic algae
Blue-green algae (cyanobacteria) can produce toxins that affect the liver, nervous system and skin. Swallowing water during a bloom can cause stomach pain, vomiting and diarrhoea. Skin contact can cause rashes, and breathing spray from the water can irritate the eyes, nose and throat. Children are at higher risk because they are smaller and more likely to swallow water.
How to spot a bloom
Toxic blooms can look like pea soup, spilled paint or green streaks on the surface, and they can also be blue, brown, white or red. Scum often collects along the shore downwind. If you can't see your feet in knee-deep water, or you aren't sure, stay out.
Don't drink untreated lake water, and don't boil it to make it safe: boiling doesn't destroy algal toxins. If you feel unwell after contact with the water, contact a doctor or Poison Control on 1-800-222-1222.
Nearby lakes with algae reports
- Herington City Lake3 km away, 32 reports, last in 2026
- Marion Reservoir31 km away, 330 reports, last in 2026
- Marion County State Fishing Lake37 km away, 78 reports, last in 2026
- Council Grove City Lake40 km away, 10 reports, last in 2026
- McPherson County State Fishing Lake44 km away, 14 reports, last in 2015
Questions about Herington Reservoir
Is there algae in Herington Reservoir right now?
Kansas has no current advisory for Herington Reservoir. The most recent sample, on 6 June 2022 at Herington Reservoir South Ramp, was below advisory levels (microcystin 0.17 µg/L, 68,457 cyanobacteria cells/mL). This site checks KDHE's advisory list every day, but lakes are only sampled after a bloom is reported, so for today's conditions check the KDHE algae bloom map and the signs at the shore.
When was the last algae bloom at Herington Reservoir?
The most recent entry in Kansas's data is from 6 June 2022 at Herington Reservoir South Ramp: a sample below advisory levels (microcystin 0.17 µg/L, 68,457 cyanobacteria cells/mL).
Has Herington Reservoir had toxic algae before?
Yes. Blooms are recorded in 2 of the 11 years from 2012 to 2022.
Can dogs swim in Herington Reservoir?
Keep dogs out of the water whenever a bloom is reported or the water looks green, scummy or discoloured. Dogs are the animals most often killed by algal toxins because they swallow water and lick their fur. If your dog swims in water that might have algae, rinse it with clean water and call a vet if it vomits, drools, staggers or seems weak.
Can you eat fish caught in Herington Reservoir during a bloom?
If you keep fish caught during a bloom, health agencies advise removing the guts and liver and rinsing the fillets in clean water before cooking, because toxins collect most in the organs. Some agencies advise not eating fish from an active bloom at all, so follow local guidance.
About this data
This page uses official records from the Kansas Department of Health and Environment (KDHE), which updated as samples come in, with advisories reviewed through the April to October season. Reports are grouped by waterbody. The site was last rebuilt on 24 October 2026.
States only test some lakes, some of the time, so a lake without a recent report hasn't necessarily been checked. This page is independent, isn't affiliated with the State of Kansas, and isn't health advice. View the source data.