The lower Broken Creek and Nine Mile Creek (referred to collectively as the lower Broken Creek) begins near Katamatite, downstream of where Boosey Creek enters Broken Creek, and then flows west to join the River Murray.
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, often contracting to isolated pools or drying out completely. The creeks now have numerous weirs and flow at a relatively constant level from mid-August until mid-May to support adjacent irrigated farming. These modifications have changed the way native animals use the creek. Previously, native fish would have moved into the creek when it was flowing and returned to the River Murray when it dried. Both creeks now provide year-round habitat for native fish, and fish passage structures allow fish to move between weir pools. Environmental water is used to support these permanent fish habitats by providing flows to support fish passage and by providing higher flows to trigger fish movement, control water quality or flush azolla as necessary.
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 to the lower Broken Creek can be sourced from both the Goulburn and Murray systems. Environmental water is sourced from the Goulburn system through the East Goulburn Main Channel and from the Murray system through the Yarrawonga Main Channel. Water is then released into lower Broken Creek from irrigation area regulators along the length of lower Broken Creek. The priority river reach for environmental watering is reach 3 (from Nathalia Weir Pool to the River Murray). Environmental flows that target reach 3 are expected to also deliver the desired flows in reaches 1 and 2. The measurement point for target flows in the lower Broken Creek is at Rices Weir.
Environmental targets can also be met by water delivered from Lake Eildon (known as inter-valley transfers) or Hume Reservoir (known as choke bypass flows) to meet downstream consumptive demands in the River Murray. These consumptive deliveries occur usually during peak irrigation demand: from spring to autumn. These flows may help achieve the desired environmental objectives without the need to release environmental water.