It was built from 1914 to 1918 during World War I to control water flows in the upper River Torrens and provide gravity-fed water to Adelaide's eastern suburbs.

It is named after the small town of Millbrook, demolished and removed during construction.

During the 1970s, the nearby town of Chain of Ponds was also removed to prevent pollution of the reservoir's water.

[1] Millbrook covers 178 hectares (440 acres) behind a 288-metre (945 ft) clay-cored earth dam.

[1] It lies on Chain of Ponds creek, a tributary of the River Torrens.