Robyn J Watts, David Crew, Luke Egan, Paul Frazier, Thom Gower, Tracey Hamilton, Sascha Healy, Xiaoying Liu, Nicole McCasker, Liticia Ross, Andre Siebers, John Trethewie, Shjarn Winkle.
About the document
The Werai Forest Report provides the findings of three projects undertaken in Werai Forest in 2021-22 as part of the Edward/Kolety-Wakool Flow-MER program. These projects will assist the future management of the forest and delivery of environmental water to the forest.
The report provides information on the findings from three components of the MER research program in the Werai Forest: hydrology, primary productivity and vegetation responses to inundation research. Also provided are reflections on the collaborative partnerships that came about as a result of informal discussions at the Werai Group whilst undertaking the three Werai projects.
Summary of Findings
Characterising the hydrology of Werai Forest using gauged hydrological data and Sentinel imagery.
- Flows into Werai Forest via Tumudgery Creek commenced when the discharge downstream of Stevens Weir was approximately 2,700 ML/d.
- Even small events (<3,500 ML/d downstream of Stevens Weir) can inundate approximately 200 ha of the forest.
- Return flows from the forest into the Edward/Kolety River commenced when the discharge downstream of Stevens Weir was between 3,152 - 3,237 ML/d. Return flows from Tumudgery Creek into Colligen Creek commenced when the discharge DS Stevens Weir was between 5,471 ML/d and 9,340 ML/d.
The duration of inundation of the forest after flooding was short-lived, with a rapid decrease in inundation extent even following large floods.
- These analyses provide fundamental information helping to describe and understand the hydrology of the system.
- Evaluation of the effectiveness of drones for assessing the response of groundcover plants to inundation.
- It was possible to remove the canopy from drone derived 3D data with less loss of ground cover than would be possible when using 2D imagery.
- Drone derived multispectral data was effective in differentiating between uniform areas of ground vegetation. However, when cover was a mixture of both bare earth and vegetation, detection was more uncertain.
- Using the normalised difference vegetation index (NDVI) it was not possible to confidently differentiate between dead and living (but brown) ground cover vegetation because dead vegetation and living (but brown) vegetation were too similar in spectral signature.
- The drone multispectral method can differentiate between different growth stages of specific species in areas of uniform cover. This is because processes such as senescing (browning at the end of season) are associated with a distinct reduction in green and near infrared light and are therefore easily identified using vegetation indices, such as NDVI. However, it becomes less feasible when using a NDVI value averaged from a 1 m2 quadrat that is made up of multiple intermixed species.
- It was not possible to use the drone imagery to differentiate between different ground cover species.
Drone imagery can be used to detect changes in ground cover vegetation condition (greenness) in response to different inundation regimes.
- The findings of this study show that the technology can be adapted to yield valuable insights and offer the prospect of rapidly capturing data over a much larger area, more frequently, than is possible with traditional ground-based ecological surveys. With continued refinement, techniques described could be applied more broadly to help inform future Commonwealth environmental watering actions and assist the management of Werai Forest Indigenous Protected Area by Traditional Owners.
Field-based experiment to examine primary productivity in flooded areas of Werai Forest following an unregulated flow event in December 2021.
- Primary production within the river channels followed a seasonal trend, increasing as temperatures increase through summer. Flooded off-channel areas within Werai Forest had higher rates of productivity than the river channels. Aquatic plants and attached algae in inundated floodplains and flood runners had very high rates of productivity (up to 10 x that of algae in the water column), with productivity being highest at peak flows.
- Our findings suggest that while planktonic production can sometimes be higher in riverine environments, the productivity of aquatic macrophytes and attached algae on floodplains can be considerable during inundation events, and do not contribute to equivalent pulses of respiration.
- Floodplain productivity may provide a substantial boost to overall primary production across the Edward/Kolety River system, which is not currently captured by conventional stream metabolism monitoring techniques. This study thus emphasises the importance of multiple measurement approaches for characterising river-floodplain production during flow pulses.
Further information
