Management of water resources in the Murray-Darling Basin has historically focussed on water security and the allocation of water for users with competing needs. This focus was reflected in the seminal paper on multiple risks to shared water across the basin by the Commonwealth Scientific and Industrial Research Organisation 15 years ago. That paper captured key concerns that were at the forefront for decision-makers, managers and policy-makers who were, at that time, experiencing the early impacts of the Millennium Drought. Water quality, then, was secondary to the issues of water security. Across the following years, new water quality risks have emerged along with a more nuanced understanding of the complex interplay between climate, floodplain/catchment vegetation, hydrology, and water quality. Critically, this improved understanding applies to the systemic shocks of extreme events, such as the 2020 bushfires and hypoxic blackwater events, as well as the variability, duration and volumes of natural and regulated river flows. In this paper, we explore the key water quality issues that currently face the Basin, and reframe water quality as an integral rather than incidental component of the risks to shared water in the Basin, with the associated implications for policy development that this implies.

Mercury (Hg) contamination is an environmental concern as a by-product of legacy mining in Australia. Here we investigate the spatial and temporal distribution of Hg in the Molonglo River system in New South Wales, Australia, and assess the physical and chemical factors influencing that distribution. Mercury concentrations in sediment cores were measured in conjunction with 210Pb and 137Cs dating to establish historical contamination. This was done at the source mine site of Captains Flat, New South Wales, and the system’s sink in Lake Burley Griffin, Australian Capital Territory. Additionally, surficial sediment Hg concentrations along the Molonglo River were analyzed to determine the spatial distribution of Hg. Analytical results showed the primary physical and chemical factors influencing Hg dispersion to be distance, total organic matter, and the presence of iron oxides and oxyhydroxides. The highest Hg concentrations were near the mine site at Captains Flat and decreased significantly with distance. Sediment core analyses in both Captains Flat and the lake showed reductions in Hg concentrations toward surficial sediment layers. It is suggested government-funded rehabilitation programs are playing a part in reducing the release of metal contamination.

Methane (CH₄) emissions in mangrove ecosystems may complicate the ecosystem’s potential carbon offset for climate change mitigation. Microbial processes and the mass balance of CH₄ in mangrove sediment are responsible for the emissions from the ecosystems. This is the follow up of our previous research which found the super saturation of CH₄ in the pore water of mangrove sediment compared to atmospheric CH₄ and the lack of a correlation between pore water sulphate and CH₄ concentrations. This study is going to investigate methane production pathways in the sediment of overwashed mangrove forests. Two approaches were used to study methanogens here: (1) the spread plate count method and the quantitative polymerase chain reaction (qPCR) method, and (2) laboratory experiments with additional methanogenic substrates (methanol, acetate, and hydrogen) to determine which substrates are more conducive to methane production. According to the qPCR method, methanogen abundance ranged from 72 to 6 × 10⁵ CFU g⁻¹ sediment, while SRB abundance ranged from 2 × 10² to 2 × 10⁵ CFU g⁻¹ sediment. According to the plate count method, the abundance of methylotrophic methanogens (the only group of methanogens capable of competing with SRBs) ranged from 8.3 × 10² to 5.1 × 10⁴ CFU g⁻¹, which is higher than the abundance of the other group of methanogens (0 to 7.7 × 10² CFU g⁻¹). The addition of methanol to the sediment slurry, a substrate for methylotropic methanogens, resulted in a massive production of CH₄ (up to 9 × 10⁴ ppm) and intriguingly the control treatments with autoclaving did not kill methanogens. These findings suggested that mangrove ecosystems in the marine environment provide favourable conditions for methanogens and further characterisation of the methanogen involved in the process is required. As a result, future research in this ecosystem should include methane production in carbon offset calculations, particularly due to methylotropic methanogenesis.

What are the benefits of engaging undergraduate students with authentic, inquiry-based curricula that develop transdisciplinary research skills? Internationally, many educators believe that research-active curricula help students better understand how scientific and technological concepts underlie the complexities of our world, especially in the context of natural resource management and sustainability. This paper describes the outcomes of a “consultancy approach” (CA) to teaching an undergraduate water resources management course in an Australian university over the past 10 years. Using the documented experiences of staff, students and clients, this paper demonstrates how this research-based curriculum has engaged students in authentic field-based research in ways that are student-centred, address diverse learning motivations and demonstrate the realities of being a practising professional. In addition, by providing environmental managers with a depth of research knowledge applicable to decision-making at individual sites that they would otherwise be unlikely, even unable, to acquire, the CA to teaching addresses the ongoing need in Australian communities for reliable scientific and environmental data on which to base complex land management decisions.