New data indicate a popular wilderness lake in the southern Wind River Range is safe for recreating. That contradicts a sampling from a few years ago, showing it was one of poopiest in the country.
A Wyoming Department of Environmental Quality (DEQ) team detected little to no fecal matter in Lonesome Lake this past summer. So why were the levels so high a few years ago?
“I would say it's largely unexplained,” said Jeremy Zumberg, DEQ’s watershed technical support supervisor.
Zumberg added it could be that contaminants were high at the particular time of testing. But also, human error.
“It could have been something with the containers used to collect the sample. It could have been the sample processing procedure,” he speculated.
In 2022, the Environmental Protection Agency (EPA) sampled almost 1,000 bodies of water in the U.S. Of them, Lonesome Lake came back the poopiest.
The federal findings were released this summer. The EPA tested for enterococci, a type of fecal bacteria, and Lonesome Lake was clocked at 384 times the concentration EPA deems safe for recreation, like swimming.
WyoFile reported the finding was in line with a long held belief in the backcountry climbing and hiking communities, where many suggested the water is unfit even after filtering.
Lonesome Lake is near the Cirque of the Towers, one of the Wind River Range’s most scenic destinations. The area is like a bowl, with the high mountain lake at the base. With thousands of people visiting every year, there’s a lot of poop resting on the dirt edges of the bowl. Each spring when the snow melts, it possibly carries the fecal matter into Lonesome Lake.
The EPA’s finding kicked off a series of follow up samplings. Most recently, Zumberg’s team hiked the 20-plus mile roundtrip five times between July and early September in 2025.
“All the data we've collected since then [EPA’s 2022 sampling] has showed something that suggested something different in terms of the human health risk at Lonesome Lake,” Zumberg said.
Notably, Zumberg’s team sampled E. coli most recently, not enteroccoci. That’s because E. coli is the fecal bacteria indicator used by the DEQ.
“E. coli is a better representative of determining whether or not a water is at risk for recreation in freshwater systems versus saltwater systems, where enterococci is more often used,” said David Waterstreet, DEQ’s watershed protection section manager, citing EPA findings. “I think it is possible that enterococci could still be high, though it would seem improbable based on what we found.”
Waterstreet couldn’t speak to the safety of Lonesome Lake for drinking, as that’s out of the purview of DEQ’s study. The Centers for Disease Control and Prevention recommends what most backcountry users already know: It’s a good idea to filter water before drinking it.
Waterstreet said DEQ is considering another round of Lonesome Lake samplings in 2026.
“Typically, if we were doing a routine monitoring event and we found these types of criteria, it would be unlikely that we would prioritize a follow up trip,” he said. “In this circumstance, due to the interest of the public, there's a greater likelihood that we will, just so we don't overlook something.”
While the lake officially has safe readings for fecal matter now, a quick Google search shows the lake still has its years-long informal “poopy” reputation.
