Mann Creek Reservoir is formed by Mann Creek Dam, which is part of the Mann Creek Project. Managed by the Bureau of Reclamation, Snake River Area Office, this 650-acre impoundment offers a 280-acre reservoir with 5 miles of shoreline. Boating and fishing are the major recreation activities at Mann Creek Reservoir, located in southwest Idaho, northwest of Boise. Fishing opportunities for rainbow trout, crappie, and largemouth bass. Season open year-round. Site offers: restrooms, boat ramps, primitive campsites, and swimming.