Update November 6, 2017
The advisory remains in place for the North Fork Virgin River. Results from the 2016 and 2017 sampling season indicate that water quality is improving on the North Fork Virgin River. However, the National Park Service continues to educate backcountry visitors about the possible health risks associated with water contaminated by E. coli bacteria.
In 2009, technicians from the National Park Service measured E. coli levels that were not meeting water quality standards for the North Fork of the Virgin River upstream of the Zion Narrows.
Since 2010, the National Park Service has issued warnings to anyone issued a permit to hike the Zion Narrows. Subsequent monitoring has revealed that multiple irrigation return flows are likely the driver of downstream E. coli exceedances.