Aug 20, 2026

Blue-Green Algae and Your Dog in Austin: 6 Deaths Since 2019, and 2 Signs to Turn Back

The City of Austin states that six dogs have died from toxins since 2019, believed to be swallowed blue-green algae, and it named Red Bud Isle in a June 2026 warning. Here are the two conditions that mean do not enter, and what to do after any contact.

Luis ZamoraCo-founder of PetCompass; Dog Dad to Banzo and Tuck

Austin, Texas10 min readPet Care & ServicesThings to Do

This is the most important page we have written about Austin, and it is about water.

The City of Austin states plainly on its own algae page: "In Austin, the deaths of six dogs have been attributed to toxins since 2019. It is believed they swallowed blue-green algae."

Austin is a city where dogs swim. Red Bud Isle, Barking Springs, the Barton Creek Greenbelt swimming holes and the whole edge of Lady Bird Lake are all part of what makes it a good dog city. So the point of this page is not to keep a dog out of the water. It is to give you the two conditions the city says should stop you, and the rinse routine that follows.

What the city publishes, and when

The source is the City of Austin Watershed Protection page, Algae in Austin's Waterways. It carries a dated status line, and when we read it the date was June 2, 2026.

That status line said: "We are beginning to see thick mats of blue-green algae, which may be toxic, at Red Bud Isle on Lady Bird Lake and at Walsh Boat Landing on Lake Austin. It may be in other places as well."

Read that Red Bud Isle mention twice. Red Bud Isle is one of the city's 30 designated off-leash dog areas. The city is warning about toxic algae at a place it also designates for dogs to run loose beside water.

Because that line is dated, treat the specific locations as a snapshot and open the page yourself before a water day. The rules of thumb below do not expire.

What the city says	Detail
Dog deaths attributed to toxins since 2019	6
Named in the June 2026 status line	Red Bud Isle, Walsh Boat Landing
Season of highest risk	summer and autumn
Toxins detected in mat samples	anatoxin-a and its variants, cylindrospermopsin, microcystin
Human swimming in Lady Bird Lake	not allowed, per City Code 8-5-48
Who to call if your dog is sick	your vet, then ASPCA Animal Poison Control or Pet Poison Helpline

The two conditions that mean do not enter

The city's guidance is short enough to memorise. Do not enter the water if:

The water is warm or stagnant, or you can see scum, film or algae. Warm and still is the growing condition. Visible scum or a film on the surface is the thing itself.

There has been rain in the past three days. This one surprises people, because rain feels like it should flush a creek clean. What it actually does is wash nutrients and bacteria off the land and into the water.

Those are the city's two tests, not ours. If either is true, the day becomes a walk rather than a swim, and Austin has 30 off-leash areas to walk in.

What to do when your dog has been in the water anyway

Four steps, all from the city's own page:

Do not let your dog drink the water. "Do not drink water directly from natural water bodies." Carry fresh water and offer it often, because a thirsty dog will drink whatever is nearest.

Avoid contact with algae. Not just avoid swallowing it. Contact.

Rinse the fur. "Rinse skin or animal fur after contact with water."

Rinse before the dog grooms itself. This is the step people miss: "Do not allow dogs to lick their fur prior to rinsing." A dog that swims, then sits on the bank licking its coat dry, is drinking whatever was in the water in concentrated form.

Carry water for rinsing as well as drinking on a lake day. It is the cheapest safety measure on this page, and a towel belongs on the list too. Our hotel stay with a dog packing list covers the rest of what a water day needs.

If your dog seems unwell afterwards

The city's instruction is immediate rather than watchful: "If your pets or livestock seem sick after going in or near water, contact a veterinarian right away."

It also names two national lines, with a warning about cost: ASPCA Animal Poison Control on 1-888-426-4435 and Pet Poison Helpline on 1-855-764-7661, noting "there is a fee for these calls."

Austin has five hospitals open 24 hours. Save the nearest one before the water day, not during it, and our how to choose a veterinarian guide covers picking one properly rather than by proximity alone. Our emergency vet, what to know guide covers what a hospital will ask you, and our pet first aid basics guide covers the twenty minutes before you get there.

Austin Public Health also asks people to report suspected cases through a Harmful Algal Suspected Illness Reporting Form linked from the algae page, in English and Spanish. That is worth doing even if your dog recovers, because the city's picture of where the toxins are is built from those reports.

What the toxins actually are

The city lists what it has found in algae mat samples since 2019: "Anatoxin-A and its variants, dihydroanatoxin-a or homoanatoxin-a", cylindrospermopsin and microcystin.

It also gives the reassuring half of the picture, and we will quote it rather than paraphrase: "Fortunately, the toxins have only rarely been found in water samples. When found in water samples, the toxins have been present at very low levels well below any safety thresholds."

Put those two facts together and the risk model becomes clear. The danger is in the mats, not in the general body of water. A dog that swims in open, moving, clear water is in a different situation from a dog that noses through a green mat at the edge or drinks from a warm stagnant pocket. That is why the city's advice is about avoiding algae rather than avoiding lakes.

Why 2019 changed things

The page is candid that this is new: "We are not aware of any human or pet health problems from harmful algae in Austin prior to 2019."

It then lists the possible contributing factors rather than claiming one cause: low flows during the 2011 to 2015 drought, the arrival of zebra mussels in 2017, flooding in autumn 2018, and climate change. It also names the thing residents can influence, high nutrient levels, and asks for two specific behaviours: reducing fertiliser and lawn chemicals, and picking up dog waste.

That last one connects this page to Austin's off-leash rules, which bar letting a dog defecate "in or near water, dry creek beds, or on streambanks" and bar leaving bagged waste on a trail for later collection. The waste rule is a water quality rule here, not a tidiness rule.

The places this bears on most

Red Bud Isle, 3401 Red Bud Trl. Thirteen acres of island below Tom Miller Dam, off leash, with water access on most of its edge. The most affected site by design, and the one the city named in June 2026.

Barking Springs, 2105 Andrew Zilker Rd. The spillway below Barton Springs Pool, one acre, on the off-leash list. Moving water rather than still, which is the better condition, but the same rules apply.

Auditorium Shores, 1100 W Riverside Dr. Three acres on the south bank of Lady Bird Lake, downtown. Note the separate point from the city's page: people are not allowed to swim in Lady Bird Lake at all, under City Code 8-5-48.

Barton Creek Greenbelt. Twelve miles of creek with swimming holes, and the city's greenbelt page is explicit that water levels are "variable and dependent on recent rainfall" and that Parks and Recreation "does not monitor water levels", pointing instead to USGS and Lower Colorado River Authority monitors. Low, warm, still water in late summer is exactly the condition the algae page warns about.

McKinney Falls State Park. A state park inside the city, and one with its own answer to this question. Its park page lists items not allowed in the Upper and Lower Falls areas includes "Pets in the water", alongside food, alcohol, glass and speakers. The state's general rule agrees: Texas State Parks states "Pets and glass containers are not allowed in swimming areas."

A season-by-season shape

The city's dog parks page says these algae "are most likely to be present during summer and fall". Combine that with Austin's heat and the year sorts itself.

Spring. The best water months, and also the months when rain is likeliest, which triggers the three-day rule. Check the forecast backwards, not just forwards.

Summer. Highest algae risk, highest heat risk, so early morning becomes the only sensible window for anything. Our summer heat safety for pets guide covers pavement testing and the early signs of heat trouble, and our Austin with a dog, month by month guide ranks the year around both risks.

Autumn. Still flagged as higher risk by the city, with the additional trap that the weather feels safe. September water in Texas is warm water.

Winter. The lowest-risk water season, and cool enough for long walks on the greenbelt.

Conclusion

Six dogs have died in Austin since 2019 from what the city believes was swallowed blue-green algae, and the city has published exactly what to do about it.

Two conditions mean no: warm or stagnant water with visible scum or film, and rain in the past three days. After any contact, rinse the fur before the dog licks it. Carry drinking water so the dog never has to choose the lake. If your dog seems unwell after being in or near water, call a vet immediately rather than waiting.

Then check the city's algae page before a water day, because the locations on it change and the page is dated for that reason.

Frequently asked questions

Has blue-green algae killed dogs in Austin?

Yes. The City of Austin states that the deaths of six dogs have been attributed to toxins since 2019, and that it is believed they swallowed blue-green algae.

Which Austin waters have had algae warnings?

In its status line dated June 2, 2026, the city reported thick mats of blue-green algae, which may be toxic, at Red Bud Isle on Lady Bird Lake and at Walsh Boat Landing on Lake Austin, and added that it may be in other places as well.

When should I keep my dog out of the water in Austin?

The city says do not enter if the water is warm or stagnant, if you can see scum, film or algae, or if there has been rain in the past three days.

What should I do after my dog swims in an Austin lake or creek?

Rinse the fur, and do it before the dog licks itself. The city specifically advises rinsing skin or animal fur after contact with water and not allowing dogs to lick their fur prior to rinsing. Also do not let a dog drink directly from natural water bodies.

What time of year is algae worst in Austin?

Summer and autumn. The city states these algae are most likely to be present during summer and fall.

Which toxins has Austin detected?

Anatoxin-a and its variants dihydroanatoxin-a and homoanatoxin-a, cylindrospermopsin and microcystin, all in algae mat samples. The city notes toxins have only rarely been found in water samples, and at very low levels well below safety thresholds.

Sources

Conditions change week by week. Check the city's algae page before any water day.