Henrys Fork (Snake River tributary)

Henrys Fork, also known as Henry's Fork of the Snake River, is a major tributary of the Snake River, located in southeastern Idaho. Rising in the mountains west of Island Park, Idaho, it flows generally southwest for approximately 127 miles (204 km) before joining the Snake River near Rexburg.

The river is renowned for its exceptional fly fishing opportunities, attracting anglers from around the world. Its diverse habitats support a healthy trout population, particularly rainbow and brown trout. Key sections known for fishing include Box Canyon, Railroad Ranch (also known as Harriman State Park), and the lower reaches near Ashton.

The river's hydrology is significantly influenced by Island Park Reservoir, a large reservoir that regulates the flow of water downstream. This regulation allows for consistent water levels and temperatures, benefiting both irrigation and the fishery. However, the controlled flows also have ecological implications that are actively managed.

Henrys Fork plays a vital role in the local economy, supporting agriculture through irrigation, tourism through recreational opportunities, and power generation through hydroelectric dams. Its management is complex, involving multiple stakeholders and balancing competing demands for water resources. The river's name honors Andrew Henry, a fur trader who explored the area in the early 19th century.