Rosslynne Reservoir is the only major storage in the Maribyrnong catchment, and it is located in the upper reaches of Jacksons Creek near Gisborne. The release capacity of 20 ML per day from the reservoir is a significant constraint on the outcomes that can be achieved by environmental flow deliveries in the Maribyrnong system. Water for the environment is primarily used to support outcomes in Jacksons Creek between Rosslynne Reservoir and the confluence with Deep Creek (that is, environmental flow reaches 6 and 7 shown in Figure 3.4.1). These two reaches are described as upper and lower Jacksons Creek respectively.
The VEWH does not hold an environmental entitlement in the Maribyrnong system, and it relies on opportunistic, temporary trade to meet demands. Each year for the last six years, Melbourne Water and the VEWH have worked with local diversion licence holders to purchase unused water that can be delivered to support environmental outcomes. This arrangement is negotiated each year and will only occur with the agreement of all parties involved.