Commonwealth Environmental Water Office Monitoring, Evaluation and Research project: Edward/Kolety-Wakool River system Selected Area technical report 2019-20

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.