The lower Broken and Nine Mile creeks have been regulated for over 100 years, significantly altering their flow regimes. Pre-regulation, the creeks would have mainly flowed in winter and spring and the adjacent floodplain would have received more regular flooding from overbank flows. In summer and autumn, the creeks would have had much less flow, even reducing to pools and drying out completely. The creeks now flow at a relatively constant level from mid-August until mid-May with numerous weirs that support adjacent irrigated farming. This has resulted in changes to the way native animals use the creek. Previously, native fish would have moved into the creek when it was flowing and moved back out into the River Murray when it dried. The creek now provides year-round habitat for native fish, permanently holding water and with fish passage structures through all the weirs. Consequently, environmental water is used to support this permanent native fish habitat.
The lower Broken Creek is operated separately to the upper Broken Creek and Broken River because regulated water is delivered to the lower Broken Creek from the Goulburn and Murray systems via the irrigation channel network, rather than from the Broken River.
Environmental water provided in the lower Broken Creek can be sourced from both the Goulburn and Murray systems. Environmental water is released from the Goulburn system through the East Goulburn main channel and from the Murray system through the Yarrawonga main channel. The priority river reach for environmental watering is reach 3 (from Nathalia Weir Pool to the River Murray), with flows to this reach expected to also deliver the desired flows in reaches 1 and 2. The measurement point for target flows in lower Broken Creek is at Rices Weir.