Gwydir River Selected Area MER Project
Newsletter 2 December 2019
In this issue:
• Core monitoring activities July - December 2019 o Hydrology o Water quality and Foodwebs o Birds o Vegetation o Turtles • Contingency monitoring activities July - December 2019 o Water quality in pool refugia o Water quality Incident response o Fire response
HYDROLOGY
Recent flows through the lower Gwydir system have been restricted to regulated deliveries of high security water, stock and domestic water, and water for the environment. Over the last three months several environmental flow events have been delivered into the Gwydir, Mehi and Carole Creek systems to re-connect previously isolated waterholes. These occurred on the 15-25 October and 9-22 December 2019. Another flow is scheduled for early in the New Year, with the purpose of maintaining and providing access to refuge habitat, increase connectivity through these channels and improve water quality in pools.
The October flow consisted of 5,000ML of environmental water from Copeton Dam which reached Tyreel and Combardello weirs and Carole Creek near Garah in early November. This was shortly followed by a WaterNSW delivery of stock and domestic water that extended water further down the Mehi, Gwydir and Carole systems.
The December release was 2,000ML delivered out of Tareelaroi weir down the Gwydir, Mehi and Carole Creeks. As of 20 December, the water had reached Tyreel weir on the Gwydir, Moree town on the Mehi, and Midkin on Carole creek.
Photo 1: Refuge pool upstream of Boolooroo Weir on the Gwydir River before (top), during (middle) and after (bottom) the October flow event.
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Newsletter 2 December 2019
WATER QUALITY AND FOODWEBS As part of ongoing water quality monitoring in refuge The MER team monitored water quality before, during and pools of the Gwydir, Mehi and Carole channels, after the October environmental flow event (Photo 2). Water continuously logging dissolved oxygen and temperature quality parameters in most of the channels and waterholes sensors have been deployed at various sites within each remained good with oxygen levels in the acceptable range for channel (Photo 4). This will allow us to monitor the aquatic animals (>4mg/L). changing conditions in these pools to inform ongoing
environmental water delivery (Figure 1). If you see these loggers please do not touch them!
Photo 2. Taking water quality samples at Combardello weirpool during the flow event in October.
However, in the Mehi River, an initial slug of poor quality water occurred (black water, Photo 3). At some points, dissolved oxygen concentrations were as low as 0.5mg/L, especially around Combardello weir. This caused a number of fish deaths (200-300 fish) along this reach of the Mehi River. The water quality of Gingham Waterhole was also poor as it dried down, with very high levels of dissolved oxygen (from Photo 4. Buoy with dissolved oxygen/temperature probe high algal growth), and high salinity and turbidity. This suspended under it.
deterioration of water quality is not unusual for a waterhole in dry times with very low water levels.
Figure 1. Water temperature in one of the monitored pools in the Mehi River. Surface temperature (orange) showed marked daily fluctuations, while at the bottom of the pool (blue) temperature is more consistent over time. Photo 3. Blackwater within the Mehi River in October 2019.
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Newsletter 2 December 2019
Micro and macroinvertebrates were also sampled within the refuge pool sites in December (Photo 5) as part of a research project into foodweb concentration and contraction during pool drydown. This was the first sampling time for this project and these data contribute to establishing the pre- drydown resource base available to aquatic fauna such as fish and turtles.
Photo 6. Post fire regrowth in the Gingham watercourse.
Photo 5. A water flea (Macrothricidae) under microscopic magnification. The pink dye (Rose Bengal stain) makes them visible against the organic matter and sediment in the sample.
BIRDS Photo 7. Vegetation site in the Old Dromana area of the lower Spring Waterbird diversity surveys were undertaken in Gwydir wetlands. November by UNE/2rog, DPIE EES and NPWS staff. Surveys were hampered by the extreme fire danger, which protracted the survey of all sites. Most sites were dry and hence TURTLES waterbird numbers were generally low, except in the Mallowa Annette Deppe, a Masters student at UNE, is and at Whittakers Lagoon, where better numbers were seen investigating the movement of turtles in the Gwydir due to recent watering of these areas. Wetlands. She has been catching, measuring and VEGETATION tracking turtles in Gingham Waterhole in the Gingham system for the last few months (Photo 8), which is Spring vegetation surveys were undertaken in late November nearly dry. She has trackers on 24 turtles in total – 9 at sites within the lower Gwydir, Gingham and Mallowa Eastern longneck and 15 Murray River turtles. Her systems. Most sites were dry except for several sites in the data suggests a very different response from the two eastern Mallowa that had been recently inundated. species, with all Murray River turtles remaining in the Vegetation cover was generally low across most of the receding pool within the Waterhole. In contrast, many Gingham sites, with many sites being recently impacted by a of the Eastern longneck turtles have walked from the fire that occurred in September. On a positive note, there was waterhole, taking refuge in leaf litter under logs in the evidence of vegetative regrowth across many fire effected surrounding woodlands. One turtle has even walked sites (Photo 6). over 2km from the waterhole! Sites in the Gwydir wetlands showed greater vegetation cover, through most of it was very dry (Photo 7).
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Newsletter 2 December 2019
Photo 9. Surveying vegetation at a sedgeland plot that was recently Photo 8. Surveying turtles in Gingham Waterhole effected by fire in the Gwydir SCA.
FIRE RESPONSE
As noted above, a fire burned around 1400ha of the Gingham watercourse within the Gwydir SCA in September 2019. This event offers an opportunity for the MER project to investigate vegetation response post-fire and how water for the environment influences this. Planning is underway to undertake surveys to compare burnt and unburnt sites for vegetation cover and diversity in water couch/sedgeland and Coolibah woodland communities (Photo 9). We are also planning to conduct mesocosm experiments to look at differences in invertebrate seedbank response to inundation from fire-affected soil samples. This will inform how the productivity of these areas has changed, and how this may change over time as the system recovers from the fire.
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