The United States Geological Survey (USGS) has issued a PSA about the safety of drinking water in backcountry of Yellowstone National Park and if you plan on exploring its 1,000+ miles of trails you should pay close attention to its warning about drinking water from its thermal features.
There are loads of drinking water refilling stations throughout the park where tourists can fill up there water bottles without threat of contamination but once you enter the backcountry all bets are off. Yellowstone water chemists advise non-thermal waters from rivers and creeks in Yellowstone, which are derived from snow and rain, are typically well suited for drinking after onsite treatment but thermal water may contain high levels of arsenic and microorganisms like brain-eating amoeba and visitors should never consume thermal water:
“Thermal water should not be used as drinking water. First, off-trail travel in thermal areas is prohibited, and the ground in thermal areas is often dangerous to traverse. In addition, thermal waters can have microorganisms that are known to be harmful, such as Naegleria (a brain-eating amoeba), and can contain elevated concentrations of arsenic and fluoride. The U.S. Environmental Protection Agency’s (EPA) Maximum Contaminant Level (MCL) for arsenic is 0.010 mg/L, and for fluoride is 4.0 mg/L. The arsenic concentration in Yellowstone thermal waters is often 1 mg/L, but concentrations as high as 17 mg/L have measured—that’s about 2000 times higher than the MCL! In addition, fluoride as high as 57 mg/L has been measured in Yellowstone thermal waters. Other nasty chemical constituents that are known to be elevated and may cause adverse health effects include antimony and mercury. So for a lot of reasons, stay away from thermal water. It is not good for your health!”
Most Yellowstone backcountry areas will have several options for obtaining safe drinking water and when topping off your supply, ask yourself “where does the water come from and is there is a thermal area upstream?” Whenever possible, choose a river or stream that does not have thermal waters draining into it.
