Colwich City Lake algae bloom status

Colwich City Lake algae bloom history

The Kansas Department of Health and Environment has tested Colwich City Lake 21 times since 2013, usually after someone reported a possible bloom. 14 samples (67%) reached at least Watch level, and 8 reached Warning level or higher.

The highest microcystin result was 450 µg/L, about 56 times KDHE's Warning threshold of 8 µg/L.

That puts Colwich City Lake in the top 15% of the 145 Kansas lakes on this site for the number of years with blooms.

When do algae blooms happen at Colwich City Lake?

At Colwich City Lake, reports are most often logged in July, September and October.

About 79% 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 Colwich City Lake algae reports

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 Colwich City Lake 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. With blooms recorded in 6 different years here, take particular care at Colwich City Lake in July, September and October.

• 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

• Woodland Park Pond Mount Hope16 km away, 5 reports, last in 2024
• McLaughin Lake16 km away, 3 reports, last in 2016
• Lake Afton21 km away, 136 reports, last in 2026
• Eagle Lake23 km away, 14 reports, last in 2025
• Chisholm Creek Park Lake24 km away, 16 reports, last in 2015

All Sedgwick County lakes with algae reports

Questions about Colwich City Lake

Is there algae in Colwich City Lake right now?

Kansas has no current advisory for Colwich City Lake. The most recent sample, on 10 August 2026, was below advisory levels (microcystin not detected, 24,358 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 Colwich City Lake?

The most recent entry in Kansas's data is from 10 August 2026: a sample below advisory levels (microcystin not detected, 24,358 cyanobacteria cells/mL).

Has Colwich City Lake had toxic algae before?

Yes. Blooms are recorded in 6 of the 14 years from 2013 to 2026, most often in July, September and October.

Can dogs swim in Colwich City Lake?

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 Colwich City Lake 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.