The Moorabool River is a tributary of the Barwon River. It flows south from the Central Highlands between Ballarat and Ballan to join the Barwon River at Fyansford just north of Geelong. The Moorabool River is a highly regulated catchment with major storages that include Lal Lal, Moorabool and Bostock reservoirs, which supply potable water to communities in and around Ballarat and Geelong. Lal Lal Reservoir is used to supply water to the Ballarat area. Water from Lal Lal is also delivered via the Moorabool River to She Oaks Weir to supply towns in the Geelong area.
The surrounding catchment is heavily farmed, with about three-quarters of the catchment area used for agriculture. Despite substantial extraction and many years of drought, the river still retains significant environmental values.
There are several large water storages including Lal Lal Reservoir in the upper reaches of the river. In the lower reach (between She Oaks and Batesford), there are nine private diversion weirs that are a significant barrier to fish. These barriers have increased the extent of slow-flowing habitat and reduced habitat diversity in the lower reach of the Moorabool, reducing the diversity and abundance of migratory fish in this part of the river.
The Moorabool is a water supply catchment for Barwon Water and Central Highlands Water. Releases are made for urban water supply by Barwon Water from Lal Lal Reservoir to She Oaks Weir. These releases contribute to environmental outcomes in reach 3a and 3b and allow more-efficient delivery of environmental water to reach 4. Barwon Water and Corangamite CMA work together to optimise these benefits.
Water allocated to the Moorabool River environmental entitlement is stored in Lal Lal Reservoir and includes passing flows that help maintain flows in the river. Passing flows are a significant component of annual streamflow and are important in maintaining baseflows through winter. The priority reaches for environmental water delivery are the reaches between Lal Lal Reservoir and She Oaks Weir (reaches 3a and 3b), as these are where the small amount of available environmental water can have the most beneficial impact. Environmental water delivered also provides benefits to significant flow-dependant values in reach 4 (which flows from She Oaks Weir down to the confluence with the Barwon River in Geelong).