The water was originally supplied by the Plenty River however the water quality was poor due to stock crossings and pollution from rural towns. The problem was solved by bypassing the Plenty River and diverting water from Wallaby Creek and Silver Creek, both originating in the Great Dividing Range feeding the Goulburn River. This mountain water was captured in the Toorourrong Reservoir system, constructed in 1883-1885, and supplies water to Yan Yean via an aqueduct to this day. During its construction, the nearby neighborhood Mernda was created and grew rapidly. Morang became South Yan Yean, and later Mernda.