Aurora Reservoir Swim Beach Closed Because Bacteria Decided to Move In

Because nothing says “summer fun” quite like a water quality advisory.

If you had a trip to Aurora Reservoir’s swim beach on your calendar, you might want to pencil in a different plan — preferably one that doesn’t involve swimming through a bacterial soup.

Aurora Water officials closed the swim beach at Aurora Reservoir after water quality testing came back with elevated bacteria levels that exceeded safe swimming thresholds. Samples flagged either E. coli levels or cyanobacteria — also known as blue-green algae — which, despite the pleasant-sounding name, is genuinely not something you want to be doing cannonballs into.

So What Actually Happened?

Bacterial blooms like this are frustratingly common at Front Range reservoirs during summer months, and Aurora Reservoir is no stranger to the drama. Warm water temperatures, abundant sunlight and nutrient runoff create ideal conditions for bacteria and algae to essentially throw a party in the water — and you are not on the guest list.

Cyanobacteria blooms are particularly nasty. Exposure can cause skin rashes, gastrointestinal illness, respiratory irritation and, in severe cases, liver damage. E. coli contamination, often linked to wildlife or waterfowl in the area, brings its own not-fun suite of symptoms.

Aurora Water conducts regular water quality monitoring throughout the swimming season, which typically runs Memorial Day through Labor Day. When test results come back hot — and not in the fun way — the beach closes until follow-up testing shows levels have returned to safe ranges.

What’s Still Open

Here’s the silver lining, if you can call it that. The swim beach closure doesn’t necessarily shut down the entire reservoir. Fishing, kayaking, paddleboarding and trail use along the 8-mile perimeter path are typically still available during bacterial closures, since you’re presumably not gulping down mouthfuls of lake water while you paddle.

The reservoir sits at about 5,100 feet elevation on the southeastern edge of the metro area and covers roughly 820 acres, making it one of the larger recreational water spots easily accessible from Denver. On a good day, it’s a legitimately solid outdoor destination. On a bacteria day, you keep your mouth closed.

When Can You Swim Again?

Aurora Water retests the water regularly once a closure is in place. Depending on conditions — cooler temperatures, wind and reduced sunlight can all help knock down a bloom — closures can last anywhere from a few days to a couple of weeks.

Your best bet is checking Aurora Water’s website or their social media channels before you load up the car with floaties and sunscreen. They update beach status as testing results come in.

The Bigger Picture

This isn’t just an Aurora problem. Chatfield Reservoir, Cherry Creek Reservoir and several other Front Range recreation spots get slapped with similar closures every summer. Climate patterns driving hotter, longer summers aren’t doing any favors here — warmer water is basically a five-star resort for cyanobacteria.

It’s one of those low-glamour realities of living in a high-desert metro area where everyone is desperately trying to squeeze every drop of outdoor recreation out of the summer. Literally, apparently.