Number 7 Dam The largest dam built on the Dee River by ount Morgan Gold Mine|Mount Morgan Gold Mining Company Limited], officially known as the No. 7 Dam, was built upstream from the mine in 1900. Due to a serious drought at the time the dam was not filled until May 1904. The wall was raised by 4.5 metres in 1999. It remained unfilled until November 22, 2000 when water poured over the top of the dam for the first time.