'Near to final' draft for independent review - 2 May 2016 Table 2. Site-specific flow indicators for small in-channel freshes for the Barwon- Darling UEA. In this table, frequency is the percentage of years in which there is the flow event. Frequency range is shown as low uncertainty to high uncertainty Magnitude: Duration Basis of magnitude Basis of duration Timing Basis of timing Freq. range Basis of frequency flow (ML/d) (days) Small scale fish To provide regular movement The typical duration of Provides regular freshes (close to between Walgett this size event in the Minimum short scale annual) for 6,000 and Tilpa, and Darling River at Bourke of 1 event movement maintenance and (Bourke access to over half 14 and the hatch time of 90% 80% – any time opportunities and condition of short- gauge) the snags and most native fish species, of the year access to ideal lived fish populations three quarters of including short-lived habitat and other aquatic species the in-channel biota benches In addition to the The minimum duration Fish response Frequency to above, some for some Murray cod to expected when the provide improved Minimum 6,000 spawning breed (from nest water temperature of 1 event breeding (Louth opportunities for in 20 development to dispersal exceeds the critical 70% between opportunities for gauge) stream specialists of larvae); considered temperature Aug - May species such as for such as Murray sufficient for other threshold (15 Murray cod cod groups of fish degrees) Promote in-stream Shorter duration as Two events in a primary carbon and nutrients are Minimum year for increases in Based on estimated productivity: 6,000 rapidly absorbed - would of 2 food supply into the frequency for provide inundation (Wilcannia 7 also provide an events river; common for 60% 45% increased – of 90% of mapped gauge) any time productivity benefits opportunity for some this type of flow to in-channel benches movement and access to of the year occur more than of river ecosystem between Tilpa and habitats, some spawning once per year Wilcannia Page 45
'Near to final' draft for independent review - 2 May 2016 Table 2. Site-specific flow indicators for small in-channel freshes for the Barwon- Darling UEA. In this table, frequency is the percentage of years in which there is the flow event. Frequency range is shown as low uncertainty to high uncertainty Magnitude: flow (ML/d) Basis of magnitude Duration (days) Basis of duration Timing Basis of timing Freq. range Basis of frequency 6,000 (Bourke gauge) Small scale fish movement between Walgett and Tilpa, and access to over half the snags and three quarters of the in-channel benches 14 The typical duration of this size event in the Darling River at Bourke and the hatch time of most native fish species, including short-lived species Minimum of 1 event any time of the year Provides regular short scale movement opportunities and access to ideal habitat 90% – 80% To provide regular freshes (close to annual) for maintenance and condition of short- lived fish populations and other aquatic biota 6,000 (Louth gauge) In addition to the above, some spawning opportunities for in stream specialists such as Murray cod 20 The minimum duration for some Murray cod to breed (from nest development to dispersal of larvae); considered sufficient for other groups of fish Minimum of 1 event between Aug - May Fish response expected when the water temperature exceeds the critical temperature threshold (15 degrees) 70% Frequency to provide improved breeding opportunities for species such as for Murray cod 6,000 (Wilcannia gauge) Promote in-stream primary productivity: provide inundation of 90% of mapped in-channel benches between Tilpa and Wilcannia 7 Shorter duration as carbon and nutrients are rapidly absorbed - would also provide an opportunity for some movement and access to habitats, some spawning Minimum of 2 events any time of the year Two events in a year for increases in food supply into the river; common for this type of flow to occur more than once per year 60% – 45% Based on estimated frequency for increased productivity benefits of river ecosystem Page 45
EWR-Barwon-Darling-draft.docx