Orderer Ibaraki Prefecture
Completion 2005
Structure and scale Gravity concrete dam, dam height: 65m; crest length: 462m; dam voltage: 531,000m³; reservoir water volume: 16,600,000m³
Location Ibaraki Prefecture
Application Multi-purpose dam

Koyama Dam was completed in 2006, and is the newest dam in Ibaraki Prefecture. It is also the largest dam in Ibaraki Prefecture. (As of 2018)