Flow delivery constraints Basin wide environmental objectives have been developed within the context of being deliverable in a working river system that contains public and private storages and developed floodplains. To understand and assess the implications of key constraints on the ability to achieve flow indicators at the Macquarie Marshes, MDBA has drawn upon a combination of existing information (e.g. Water Sharing Plans, flood warning levels) and practical knowledge of river operators supported by testing using modelling. The watering requirements (and thus objectives) of Section 5 are met through an appropriate water delivery regime. Implementation of a delivery regime is potentially subject to a number of constraints that may mean that environmental requirements are not met at all times. An example of the constraints that apply to water delivery to the Macquarie Marshes is given below: Prolonged flows of more than about 4,000 ML/d at Marebone Weir will cause flooding of Gradgery Lane. Under current operating practices high priority is given to minimising the period that a flow of 4,000 ML/d at Marebone Weir is exceeded. Recognising that the delivery of environmental flows is highly on existing system constraints, the site-specific flow indicators for the hydrologic indicator sites across the Basin have been classified into three broad types (Table 6). Despite the delivery of environmental flows being highly dependent on existing system constraints, the site-specific flow indicators for Macquarie Marshes are considered to be deliverable as mostly regulated flows under current operating conditions. Table 6 Site-specific flow indicators for the Macquarie Marshes and effect of system constraints Site-specific ecological targets Site-specific flow indicators Provide a flow regime which ensures the current extent of Achieve a total in-flow volume of 100 GL during native vegetation of floodplain and wetland communities is June to April for 80% of years sustained in a healthy, dynamic and resilient condition Achieve a total in-flow volume of 250 GL during Provide a flow regime which supports the habitat requirements June to April for 40% of years of waterbirds and is conducive to successful breeding of colonial nesting waterbirds Achieve a total in-flow volume of 400 GL during June to April for 30% of years Provide a flow regime which supports recruitment opportunities for a range of native aquatic species (e.g. fish, frogs, turtles and invertebrates) Achieve a total in-flow volume of 700 GL during Provide a flow regime which supports key ecosystem June to May for 17% of years functions, particularly those related to connectivity between the river and the floodplain
Flow delivery constraints Basin wide environmental objectives have been developed within the context of being deliverable in a working river system that contains public and private storages and developed floodplains. To understand and assess the implications of key constraints on the ability to achieve flow indicators at the Macquarie Marshes, MDBA has drawn upon a combination of existing information (e.g. Water Sharing Plans, flood warning levels) and practical knowledge of river operators supported by testing using modelling. The watering requirements (and thus objectives) of Section 5 are met through an appropriate water delivery regime. Implementation of a delivery regime is potentially subject to a number of constraints that may mean that environmental requirements are not met at all times. An example of the constraints that apply to water delivery to the Macquarie Marshes is given below: Prolonged flows of more than about 4,000 ML/d at Marebone Weir will cause flooding of Gradgery Lane. Under current operating practices high priority is given to minimising the period that a flow of 4,000 ML/d at Marebone Weir is exceeded. Recognising that the delivery of environmental flows is highly on existing system constraints, the site-specific flow indicators for the hydrologic indicator sites across the Basin have been classified into three broad types (Table 6). Despite the delivery of environmental flows being highly dependent on existing system constraints, the site-specific flow indicators for Macquarie Marshes are considered to be deliverable as mostly regulated flows under current operating conditions. Table 6 Site-specific flow indicators for the Macquarie Marshes and effect of system constraints Site-specific ecological targets Site-specific flow indicators Provide a flow regime which ensures the current extent of native vegetation of floodplain and wetland communities is sustained in a healthy, dynamic and resilient condition Provide a flow regime which supports the habitat requirements of waterbirds and is conducive to successful breeding of colonial nesting waterbirds Provide a flow regime which supports recruitment opportunities for a range of native aquatic species (e.g. fish, frogs, turtles and invertebrates) Provide a flow regime which supports key ecosystem functions, particularly those related to connectivity between the river and the floodplain Achieve a total in-flow volume of 100 GL during June to April for 80% of years Achieve a total in-flow volume of 250 GL during June to April for 40% of years Achieve a total in-flow volume of 400 GL during June to April for 30% of years Achieve a total in-flow volume of 700 GL during June to May for 17% of years
EWR-Macquarie-Marshes.docx