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UPDATE: 9th March 2012 - for the information of ECAOAC members & local landholders across the Lower Gwydir floodplain.

GWYDIR FLOWS UPDATE 15– 6 Mar Feb 2012

Flood waters across the wider floodplain are now receding very slowly, with some paddocks on floodplain only just starting to dry back, all will take some time to fully dry down. Significant amounts of water remain in the wetlands although water levels are dropping as inflows also reduce. Most recently, over the last week, flows have started to decrease significantly into the wetlands. Flows into Gingham and Lower Gwydir appear to be a combination of Water Sharing Plan - rules based 3T water, some local runoff from storms and possibly maybe a share of last of higher flows from flood event. The Water Sharing Plan (WSP) Rule Based 3T flows (Halls, Myall and Horton) have stayed below 500ML/day since 28 Feb 2012. This rule based 3T flow is shared equally between Gingham and Lower Gwydir. Rule Based 3T water for Gwydir Wetlands has for the first time in the last week (since 28 Feb) dropped to under 500 ML/day. Flows are now back to 374 ML/day, split 50/50 @ 187 ML/day each for Lower Gwydir and Gingham with a 3-5 day delay for flow delivery. There has been only a further 2,186 ML of inflow into Copeton Dam (98.2%) over the last 7 days, but Copeton Dam releases have tapered of to around 6,302 ML for the last 7 days. Table 1. Key flow trends for Gwydir Wetlands 28 February 2012. Gauge Daily flow

(ML/day) or height (m) 6 Mar 2012

Notes

Halls Creek @ Bingara 61 Steady to very slowly dropping Myall @ Molroy 64 Dropping very slowly Horton @ Rider 249 (3T total 374) – Dropping slowly Gwydir @ Pallamallawa 2,103 Dropping steadily

Gwydir @ Yarraman 710 Small rise after steadily dropping to 650ML/day yesterday

Gingham @ Teralba 222 Small rise after dropping steadily down to 162 ML/day yesterday

Gingham @ Tillaloo 206 Steadily dropping Gingham Bridge 102 Slowly dropping Gwydir @ Brageen 300 Steadily dropping Gwydir @ Allambie 195 Steadily dropping

Gwydir @ Millewa 179 Steadily trending down but with ups and downs

Gwydir @ Old Dromana Reg 1.11 Dropped slightly. Very slowly dropping but with ups and downs

Waterbird observations & nesting requirements Observations from helicopter on 6th March 2012 showed that the majority of Egrets nesting in the ‘Belah’ and ‘River Cooba’, at various heronry locations across the wetlands, have chicks at point of fledge. Water requirement for these species are mostly related to broad foraging areas for adults feeding chicks and for chicks after fledging. Theses species are well provided for by current well watered wetlands and wider floodplain conditions. Also observed was a large increase in Ibis numbers, a small number (200-300) Magpie Geese and a similar number of Glossy Ibis had congregated in the Gwydir, since last survey. There was also significant increase in nesting Straw-necked ibis, since those observed on the flight on 27th February.

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It is now clear that the Ibis have responded as predicted, going for a second round of egg laying at both sites in the Gingham - (Lynworth site and the Old Boyanga - Curragundi - Molladree site.) It would also appear that the Ibis have stayed within the previously mapped rookery sites. Ibis are species that generally nest in colonies, preferring low and/or ground vegetation. The species also require water levels in and around their rookeries sites to be kept constant to achieve a complete and successful cycle. Without constant water levels and required depth around nests, Ibis will abandon egg and/or chicks. Unfortunately, little is known of the lowest depth of water levels that will stimulate Ibis nest abandonment. Therefore, as inflows reduce and water levels recede, there now is a key requirement for water levels in around rookery sites to be maintained at a reasonably steady level @ both the Upper and Lower Gingham nesting sites. At the commencement of this current Ibis nesting event, inflows at key upstream gauges averaged around 548 ML/day at Teralba, 541 ML/day at Tillaloo and 306 ML/day at Gingham Bridge. Flows over the last 7 days have dropped to av. 436 ML/d at Teralba and 136 ML/day at Gingham Bridge. Gingham Bridge gauge serves as lower boundaries for the flows required at these two gauges to support this bird breeding event. This information indicates and an initial inflow of up to 450ML/day in combination with the receding WSP 3T flows is required and will also need to be monitored for ongoing adjustments as the Ibis progress through their breeding cycle. (see Figure 1. below)

Gingham daily flows

-

500

1,000

1,500

2,000

2,500

3,000

3,500

15/0

2/20

12

17/0

2/20

12

19/0

2/20

12

21/0

2/20

12

23/0

2/20

12

25/0

2/20

12

27/0

2/20

12

29/0

2/20

12

2/03

/201

2

4/03

/201

2

6/03

/201

2

Date

Da

ily

flo

w (

ML

/da

y) 50% 3T share

Teralba

Tillaloo

Ging Bridge

Figure 1: Graph of recent flows at relevant gauges in the Gingham system.

Breeding cycles & flow considerations By reviewing previous aerial observations and flow gauge information, it is estimated that new Ibis nesting & egg laying commenced from approx 22 Feb. Incubation of the species is approx. 25 days and further 30 odd days to fledging stage. Total species cycle approx. 55 days (approx. 8 weeks). Observation on the 6th March showed the majority of nesting Ibis with eggs, therefore clutch completion is also set at 6th/7th March. Given 55 days from the 7th March for completion of cycle. Therefore there is a requirement for supporting flows/water levels in & around rookery sites until end of April 2012. It is likely that fledging will occur over a two-three week period at the completion of the Ibis cycle.

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Without recent catchment rainfall and river flows, the WSP rule based (3T) flows will continue to gradually reduce, as such there is a real need to consider starting an environmental water order into the Gingham Watercourse Wetlands. The aim of the delivery would be to keep the Gingham at Tillaloo Gauge at initially around a total daily flow rate of 450 ML/day, and should take place sometime in the next 2-7 days (allowing for delivery time).

Pic. 1. Lower Gingham Rookery – Ibis on nests with eggs.

Pic. 2. Upper Gingham Rookery – Ibis nests across the wetlands

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Background & ECAOAC considerations Two flooding events occurred this season in Gwydir Catchment, a moderate flood in November 2011 and a major event in early Feb 2012. Total flows for the larger Feb event (600 GL) were slightly higher than the 1976 event but with less volume. Both events provided wide scale flooding across the lower floodplain, including agricultural lands and the Gwydir Wetlands system. As a result numbers of Ibis & Egrets were enticed to congregate and nest in the Gwydir by the November 2011 flooding.(See update 20th Jan 2012). As a result of flooding & limited ground access, OEH moved to a remote monitoring phase to track waterbird nesting condition. This phase included regular aerial surveys combined with daily flow gauge monitoring. The more recent Feb 2012 flooding significantly disturbed the Ibis breeding event in the Gingham Watercourse. The Egrets have continued their cycle, unimpeded by recent flooding. (See update 16th Feb 2012)

Egrets are now @ point of fledging and the Ibis have recommenced nesting, after water levels sufficiently receded. A helo flight (6th March)conducted by OEH & CEWH staff, clearly observed an increase in Ibis numbers @ the two rookery sites and that the majority of Ibis are currently incubating eggs in nests located on ground material and low lignum shrub lands. Water levels in & around both Ibis rookeries have fallen in the past two weeks, particularly @ the upstream ‘Lynworth’ (upper Gingham) site. (see map included in this update). Daily flows measured @ the closest upstream gauges have continued to reduce as WSP (3T) rule based water has receded in the system. Daily flow rates @ the time Ibis recommenced nesting were 400-500 ML per day. The 1998/99 breeding event saw a similar flow rate of 450 ML delivered from ECA account, into the Gingham, to support successful Ibis breeding. This planned ECA water delivery is not expected to add water to the higher floodplain and dryland cropping lands, flooded by the Feb. 2012 flooding event. This wide scale natural flooding is now receding and will continue to dry down across the floodplain. A relatively small proportion of unplanted cultivated areas remain wet and are likely to remain so, in those areas closest to the Gingham Channel, during the period of this delivery. Large natural flows that may occur during this period of delivery in the system, pose the greatest potential risk of wider scale flooding. Should large natural flows be received during this period, environmental flows will be curtailed, until natural flow rates recede. Whilst difficult to estimate, additional water into the Gingham Watercourse, to support the Ibis, may be required until the end of April 2012. Limited ground access to these breeding sites has now opened and field work will now be undertaken. A teleconference, held on Monday 5th March 2012 with Gwydir ECAOACommittee discussed the current state of Ibis rookeries in the Gingham Watercourse Wetlands. All members present, endorsed a delivery to support the waterbird breeding event. Member advise that within the ECA account, a volume of 15 GL, previously set aside by the Committee for this purpose should be now used. After that volume was used NSW & Comm should be encouraged to contribute water for a successful outcome of the current event

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Gwydir ECAOAC Flow Recommendation

1. A delivery of targeted environmental flows to support the current colonial waterbird breeding event, ie. Ibis rookeries located in two locations within the Gingham Watercourse Wetlands. (see map included)

2. In combination with current receding WSP (3T) rule based low flows, provide flows

from Tyreel Weir into the Gingham Watercourse, up to 450 ML per day @ downstream Teralba Gauge.

3. OEH will review daily delivery rates as the breeding event unfolds. Intended flow

adjustments & advise to local State Water will be provided to E. Water Manager via regular internal reporting.

4. Expected event completion end April 2012.

OEH Monitoring of current event

The current system of water flow monitoring will assist in targeting and assessing flows, whilst determine updated risks to Ibis rookeries ie. inflows Upper Gingham @ Tillaloo Bridge, Gingham Waterhole & flows reaching Gingham Bridge and a significant rise in daily flows at these gauges. Temporary depth gauge plates & cameras will be deployed at key locations, above & below rookery sites, to assist water management throughout the event. Regular field visits planned 12-16th , 16th -30th March & throughout April. Water conditions in & around rookeries sites will be assessed during these visits on an ongoing basis. Adjustment to daily flow rates may be required as a result of field observations. General waterbird monitoring ie. counts and stage of chick development will be undertaken during site visits. An estimate of event success will therefore be provided at completion of breeding cycle, exp. later April 2012.

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Figure 1 Flight path of aerial survey on 8 February 2012 and locations of waterbird colonies (Credit: Simon Hunter, OEH).

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Provided as advice to ECAOAC members and landowners in the Gwydir Watercourses and Floodplain Areas by Daryl Albertson - Gwydir Environmental Water Manager NSW Office of Environment & Heritage Email: daryl.albertson@environment.nsw.gov.au or jane.humphries@environment.nsw.gov.au

http://brg.cma.nsw.gov.au/index.php?page=ECA