Diversion Dam and Deer Flat Embankments, Historic dam and embankment system in Ada County and Canyon County, United States.

The Diversion Dam and Deer Flat Embankments is the National Register name for three dams in southwestern Idaho near Boise and Nampa: the Boise River Diversion Dam and the Deer Flat Upper and Lower Embankments. They are parts of the Bureau of Reclamation's Boise Project, built to irrigate 500,000 acres of Treasure Valley farmland with the New York Irrigation District, and the Boise River Diversion Dam also generates hydroelectric power.

The three dams were built as part of the Bureau of Reclamation's Boise Project to irrigate 500,000 acres of Treasure Valley farmland with the New York Irrigation District. The Boise River Diversion Dam also added hydroelectric capacity. All three were listed on the National Register of Historic Places in 1976.

The dams take their name from the Bureau of Reclamation's Boise Project, and the Deer Flat embankments hold water for the reservoir beside Deer Flat National Wildlife Refuge. The New York Irrigation District, working with the New York Canal, distributes the stored water to Treasure Valley farms, so the structures remain working irrigation infrastructure rather than monuments.

The Boise River Diversion Dam sits on the Boise River near Boise, while the two Deer Flat embankments hold water at Deer Flat near Nampa; the three are separate sites in Ada and Canyon counties. The Boise River Diversion Dam carries a powerhouse for hydroelectric generation. The dams were listed on the National Register in 1976 as components of the Bureau of Reclamation's Boise Project.

The system combines the Boise River Diversion Dam with two earth embankments, serving a dual purpose as both an irrigation supplier and a source of hydroelectric power. This combined approach to water management and power generation was an innovative solution when it was first built.