Work on Nepean Dam started in 1925, but was interrupted for a few years by the Depression and resumed in 1933. Materials were hauled on a standard gauge railway line from the main southern line near Bargo.The dam was finally completed in 1935 and cost about $12.3 million. After several years of extremely low rainfall in the catchment, heavy rainfall in October 1938 saw the dam finally reach capacity and overflow via its spillway. Nepean Dam was upgraded in 1992 at a cost of $30 million. It was strengthened by post-tensioned anchors and a downstream rockfill embankment and further safeguarded by a concrete lined side spillway on the right abutment.
- Height: 82 metres
- Length: 216 metres
- Capacity: 70,170 megalitres
- Catchment: 320 square kilometres
- Lake: 3.3 square kilometres