About the documents
The summary and technical reports present the 2019-20 results from the Commonwealth Environmental Water Office's Monitoring Evaluation Research (MER) Project in the Edward-Kolety-Wakool River system. Monitoring activities implemented in 2019-20 included the monitoring of hydrology, water quality and carbon, stream metabolism, aquatic and riverbank vegetation, and fish movement, reproduction, recruitment, and fish community.
The reports also provide information on the findings from four components of the MER research program in the Edward-Kolety-Wakool River system: physical habitat, primary productivity, fish spawning, and e-DNA research. An overview of community engagement and communication activities also undertaken by the project team is also provided.
Key environmental outcomes include:
- Winter watering maintained longitudinal connectivity of habitat and prevented cease to flow in winter. Winter flows have many ecosystem benefits including preventing the exposure of acid sulphate soils and maintaining water quality in the lower section of the Wakool river; enabling fish to move into and out of the river system; maintaining local habitat for sedentary fish and other aquatic organisms over winter; preventing frost damage of aquatic plants; and limiting exposure of rhizomes to damage by feral pigs.
- Winter watering increased primary productivity. Maintaining flow during winter can help maintain populations of zooplankton and other invertebrates that feed on phytoplankton and periphyton, and in turn, this increases food availability for fish and other higher order consumers during periods in which food availability might otherwise be low.
- Winter watering increased opportunities for movement of fish. Silver perch responded more to winter watering than golden perch and Murray cod.
- Spring watering maintained good water quality, increased productivity, increased germination, flowering and dispersal of riverbank plants, and increased spawning in some fish species with more bony herring larvae and Australian smelt larvae being found in river zones that received environmental water compared to the upper Wakool River that did not receive environmental water.
- Environmental watering is supporting long-term recovery of aquatic and riverbank plants after being mostly eliminated in the river by the 2016 flood.
- Environmental watering is supporting fish recruitment with 2019-20 results showing Murray cod recruits being detected in the mid Wakool River for first time since 2015-16. The winter 2019 watering action may have assisted the movement of adult Murray cod into the mid Wakool River, with the spring 2019 watering action supporting the survival and recruitment of larvae.
- Environmental watering is supporting recovery of the fish community. During fish community sampling in the mid Wakool River the 2019-20 results suggest that Murray cod relative abundance and biomass continues to increase following fish kills in 2016. Bony herring were present at the highest relative abundance observed in the program, reflecting a strong spawning and recruitment year. The golden perch population continues to exhibit no recruitment and is predominantly comprised of large adults. The abundance of introduced fish species was low. Eastern gambusia were absent, almost no carp recruits were recorded, and there was decreased abundance and biomass of adult carp.
The information from these reports is being combined with other MER Project Selected Areas to provide a Basin-scale evaluation of the outcomes of water for the environment.
Key results from the research projects also reported on include:
- Edward-Kolety River physical habitat research project investigated the impacts of flow events on physical habitat of the riverbank in two reaches of the Edward-Kolety River and one reach in Colligen Creek. This study highlights the important role that historic flow patterns play on influencing future erosion events. In systems like the Edward-Kolety River, where historic flow patterns have led to excessive notching within channels, the influence of environmental water actions or unregulated flows on bank condition cannot be studied in isolation. If the management of operational flows does not change, then the potential benefits to bank condition as a result of environmental watering actions-will not materialise. If this is not possible to change operational flow delivery then environmental flow deliveries need to be designed with the position of the existing notch considered, with close attention to the rate of flow recession to minimise mass-failure events.
- Edward-Kolety River primary productivity research project aimed to advance understanding of gross primary production and ecosystem respiration in the Edward-Kolety River downstream of Stevens Weir, due to potential for flows to inundate parts of Werai Forest, connecting low-lying floodplains, anabranches and floodplain wetlands and runners that sometimes return discharge back into the river. Examination of Sentinel satellite imagery suggests that low-lying areas prone to inundation are more likely to occur in the centre of Werai Forest than along the Edward-Kolety River. These inundated floodplain wetlands within Werai Forest may act as a strong “sink” for nutrients and carbon (i.e. retained within the system and either incorporated into organism biomass or deposited) rather than exported downstream to support in-channel respiration.
- Fish spawning research in the Edward-Kolety River research project was undertaken as a citizen science project through collaboration between Charles Sturt University and the Edward-Wakool Angling Association. The aim of the research was to determine if golden perch and silver perch spawn in the Edward-Kolety River downstream of Steven’s Weir. In 2019-20 there was no indication of golden or silver perch spawning at the three study sites in the Edward-Kolety River as evidenced by the lack of eggs or larvae of golden perch and silver perch. Regardless of this result, further monitoring over a longer period of time is warranted as these are long-lived species that may not spawn every year. The project demonstrated that collaboration between researchers and community groups is an effective way to undertake research and engage the local community, draw on local expert knowledge, provide local employment and training, and make cost savings and reduced carbon emissions due to reduced travel.
- Targeted eDNA research to identify presence and spatial distribution of threatened, uncommon and iconic species project aimed to use a targeted, single species eDNA method to identify the presence and spatial distribution of threatened, uncommon and iconic species in the Edward-Kolety-Wakool system. A total of 10 sites were sampled. Murray cod were detected at 8 of 10 sites and trout cod were detected at 4 of 10 sites. Silver perch were detected in 7 of 10 sites and redfin perch were detected at a single site. Platypus were not detected at any sites, however two samples were determined to be false positives and this will be sequenced to check if the qPCR product is platypus. Dwarf flathead gudgeon, freshwater catfish and Murray crayfish were not detected at any of the 10 sites. In conclusion the project found that once assays have been developed and tested, targeted eDNA is an effective method to detect the presence of rare and threatened species. It is particularly suitable to document the distribution of species that are inefficiently sampled by other methods. The researcher team recommend future work explores occupancy modelling to enable detection probabilities to be estimated. This eDNA approach could potentially be used to identify population expansion as a result of environmental watering.