Monitoring - Lower Murray-Darling

Monitoring Evaluation and Research

Monitoring and evaluating the use of water for the environment is helping to build knowledge about the best way to improve the health of the rivers and wetlands of the Basin, based on what works and what doesn’t work.

The Commonwealth Environmental Water Office (CEWO) works with Basin states, water delivery partners, the Murray-Darling Basin Authority, scientists and the local community to build this knowledge. There are a number of programs currently underway in the Lower Murray, including the CEWO’s Monitoring, Evaluation and Research program and The Living Murray.

CEWO Monitoring, Evaluation and Research (MER) Program

SARDI undertaking fish surveys in the Lower River Murray. Photo: CEWO

To make sure the use of water for the environment in the Lower Murray is informed by sound science, the CEWO supports a long-term program of monitoring, evaluation and research in the region. A consortium team of scientists led by the South Australian Research and Development Institute (SARDI) monitor a range of targeted outcomes for fish populations and recruitment, vegetation, microinvertebrates, matter transport, Coorong habitat, stream metabolism, water quality, hydraulics and hydrology. Where watering actions target other outcomes or if knowledge gaps are identified, additional monitoring and/or research may also be undertaken. For more information on recent monitoring activities and findings refer to SARDI’s quarterly Lower Murray monitoring and outcomes newsletter.

The CEWO Monitoring, Evaluation and Research (MER) (Flow-MER) Program integrates and replaces monitoring and research activities under the Long-Term Intervention Monitoring (LTIM) and Environmental Water Knowledge and Research (EWKR) projects.

Some recent learnings in the Lower Murray include:

Environmental flows substantially increase salt export out of the Basin, reduce salt import into the Coorong and reduce salinity concentrations in the Coorong. Flows have prevented around 3.2 million tonnes of salt building up in the Coorong from 2017 to 2021, avoiding catastrophic impacts that would have been reminiscent of those experienced during the Millennium Drought.
For most years, water for the environment flowing to the end of the system is the main way that excess salt is removed from the Murray-Darling Basin. For example in 2019-20, Commonwealth environmental water contributed 100% of the 623,999 tonnes of salt exported from the Basin. This is the equivalent of over 30,000 semi-trailers each carrying a full load of salt (around 20 tonnes).
Environmental water increases the amount of “flowing habitats” and promotes water level variability in habitats. Flowing habitats benefit native plants and animals adapted to a riverine environment, whilst variable water levels generally improves bank vegetation health and increases the diversity of biofilms (key component of riverine food webs).
Environmental water transports microinvertebrates (zooplankton) from upstream sources to the Lower Murray, and increases the occurrence of littoral (bank) organisms in the main channel. Boosting the diversity (variety) and density (amount) of microinvertebrates in the Lower Murray means a more diverse food source available for predators (like young native fish).
Environmental water helps to maintain good oxygen levels in the water (>5 mg/L during dry years), by increasing water mixing. This is particularly important during the main fish spawning season (spring-summer), when early life stages (e.g. eggs and larvae) require adequate oxygen.
Spawning of golden and silver perch has occurred in the Lower Murray River, with a low level of recruitment occurring between 2015–2019 and a larger golden perch recruitment event in 2021/22. These young cohorts are helping to increase the resilience of the Lower Murray golden perch population which is dominated by nine to eleven year old fish.
Flows above 20,000 megalitres per day are likely necessary to provide suitable conditions for large perch recruitment events in this region.
Water for the environment is crucial for providing healthy estuarine conditions in the Coorong and benefiting native fish species. Over the past five years, water for the environment has supported a continuous connection between the Lower Lakes and the Coorong, generating favourable habitat and maintaining salinity levels in the Coorong lagoons below maximum thresholds despite dry conditions. Consecutive years of good recruitment of diadromous fish species such as congolli and common galaxias have seen populations rebuild, while both pouched and short-headed lamprey are migrating through the site in increasing numbers after an absence from recordings from 2007-2010.

Current Monitoring, Evaluation and Research Plan for the Lower Murray for 2019-2023

Native fish surveying in the Lower River Murray. Photos: CEWO

River Murray Channel Monitoring Plan 2021-22 to 2025-26

During 2020-21, environmental water managers from Basin state and Commonwealth agencies collaborated to develop a five-year monitoring plan for the River Murray Channel.

The Plan focuses on monitoring River Murray system scale responses to coordinated water for the environment delivery in the Southern Connected Murray-Darling Basin. It builds on existing monitoring programs to fill gaps and to evaluate ecological responses to flow at a system scale, to inform and improve the way water for the environment is managed.

Implementation of the Plan is expected to significantly improve monitoring coverage in the River Murray, focusing on productivity and fish indicators that will directly inform improved management and coordination of flows. Monitoring for 2022-23 is underway, with reporting on 2021-22 results to be published once finalised.

The Plan was developed by the monitoring sub-group of the Southern Connected Basin Environmental Watering Committee, including representatives from the New South Wales Department of Planning, Industry and Environment: Environment Energy and Science, Victorian Environmental Water Holder, South Australian Department of Environment and Water, Murray-Darling Basin Authority and Commonwealth Environmental Water Office, with support and guidance from a team of scientific experts.

The Plan is available at: River Murray Channel Monitoring Plan 2021-22 to 2025-26