The Mad River is reported to have the highest concentration of swimming holes per river mile than any other river in Vermont and sees much use from locals and visitors alike. If swimmers are curious about the risk of illness they face swimming in the Mad River, information about the water quality is available courtesy of a volunteer monitoring program called Mad River Watch, sponsored by local watershed conservation group Friends of the Mad River (FMR).

The group monitors Escherichia coli (E. coli) levels at 36 sites throughout the watershed on six dates throughout the summer months. Results are posted online at, in The Valley Reporter and on signs at select swim holes.

E. coli is used as an indicator of fecal contamination in recreational waters; the higher the level of E. coli, the greater likelihood that swimmers may contract a water-borne illness.

In 2011, the Mad River Watch signs located at Riverside Park in Warren and at the covered bridge in Waitsfield were washed away by floodwaters of Tropical Storm Irene. The remaining wooden signs were in various stages of decay due to exposure to the elements.

FMR received funding from the Lake Champlain Basin Program's (LCBP) Local Implementation Grants program to replace seven Mad River Watch signs throughout the watershed. LCBP, in partnership with the New England Interstate Water Pollution Control Commission, offers funding for pollution prevention and education and outreach projects focused on improving water quality in the Lake Champlain Basin. The Mad River is a sub-basin of the Winooski, one of the larger basins that empty into the lake.