Rainbow Lake Water Testing Results

Recently, blue-green algae found in ponds in public parks around the country has been reported to cause illness or death in dogs. Blue-green algae, while it is present in many ecosystems and is often harmless, can occasionally produce toxins that can harm dogs if ingested.

Tests of Rainbow Lake revealed this week that there is blue-green algae present in the water, and that some toxins were being produced on the day of the testing. The lake’s toxin levels are in the EPA’s non-harmful range for human contact, but because dogs are more likely to ingest lake water, it’s best to be even more cautious. (The EPA does not publish contact thresholds for dogs.)

Overton Park Conservancy asks our visitors to comply with City of Memphis ordinance 8-16-6 and leash dogs at all times in the park, with the exception of inside the gates at Overton Bark. Potable-water fountains for dogs are located inside Overton Bark so they won’t need to go thirsty on their park visits. We will be popping up some signage near the lake to remind visitors to keep dogs out of the water.

Algae is a regular presence in Rainbow Lake due to its shallow depth, its lack of moving water, and our warm climate. Nonpoint-source pollution (such as oils, dog waste, pesticides, and fertilizers) can also produce phosphorus and nitrogen that find their way into the lake and promote algae growth. All these variables can affect the level of toxins present on any given day in the lake.

As cooler weather arrives, algae growth generally slows down, but for your dogs’ safety, please allow them to enjoy the open areas of the park only when securely leashed.