Murray-Darling Research Articles

Are environmental water requirements being met in the Murray–Darling Basin, Australia?

Context In implementing the Murray–Darling Basin Plan, jurisdictions have defined environmental water requirements (EWRs) for sites along Basin rivers. EWRs are the flows (frequency, magnitude, duration, and timing) required to achieve environmental outcomes; they are derived from flow-ecology relationships by using best available scientific knowledge. Aims To assess EWR achievement across the Murray–Darling Basin over a 43.5-year period (1 July 1979 – 31 December 2022) that included periods of drought as well as widespread flooding. Methods By using a published EWR assessment tool, we analysed the achievement of EWRs for small fresh, large fresh, bankfull and overbank flows for 23 sites. Key results At 65% of stream gauge sites assessed, most EWRs evaluated had not been met. We also compared analyses of different time periods, namely, a 43.5-year period, and a 10-year period since the Basin Plan was legislated. This highlighted some improvement in EWR achievement for the small fresh EWR. Conclusions and implications Despite some improvements, the continued lack of achievement in meeting EWRs is likely to be a major contributing factor to the ongoing poor health of channel, wetland (including Ramsar wetlands) and floodplain ecosystems across most of the rivers of the Murray–Darling Basin.

Improved Wetland Mapping of a Highly Fragmented Agricultural Landscape Using Land Surface Phenological Features

Wetlands are integral components of agricultural landscapes, providing a wide range of ecological, economic, and social benefits essential for sustainable development and rural livelihoods. Globally, they are vulnerable ecological assets facing several significant threats including water extraction and regulation, land clearing and reclamation, and climate change. Classification and mapping of wetlands in agricultural landscapes is crucial for conserving these ecosystems to maintain their ecological integrity amidst ongoing land-use changes and environmental pressures. This study aims to establish a robust framework for wetland classification and mapping in intensive agricultural landscapes using time series of Sentinel-2 imagery, with a focus on the Gwydir Wetland Complex situated in the northern Murray–Darling Basin—Australia’s largest river system. Using the Google Earth Engine (GEE) platform, we extracted two groups of predictors based on six vegetation indices time series calculated from multi-temporal Sentinel-2 surface reflectance (SR) imagery: the first is statistical features summarizing the time series and the second is phenological features based on harmonic analysis of time series data (HANTS). We developed and evaluated random forest (RF) models for each level of classification with combination of different groups of predictors. Our results show that RF models involving both HANTS and statistical features perform strongly with significantly high overall accuracy and class-weighted F1 scores (p < 0.05) when comparing with models with either statistical or HANTS variables. While the models have excellent performance (F-score greater than 0.9) in distinguishing wetlands from other landcovers (croplands, terrestrial uplands, and open waters), the inter-class discriminating power among wetlands is class-specific: wetlands that are frequently inundated (including river red gum forests and wetlands dominated by common reed, water couch, and marsh club-rush) are generally better identified than the ones that are flooded less frequently, such as sedgelands and woodlands dominated by black box and coolabah. This study demonstrates that HANTS features extracted from time series Sentinel data can significantly improve the accuracy of wetland mapping in highly fragmentated agricultural landscapes. Thus, this framework enables wetland classification and mapping to be updated on a regular basis to better understand the dynamic nature of these complex ecosystems and improve long-term wetland monitoring.

Destocking waterways: Evidence that stocked Murray Cod (Maccullochella peelii) were extracted at pumped irrigation diversions within 24 hours of release

SummaryMillions of native fish are entrained into irrigation pumps in Australian rivers every year. It is often assumed these fish are wild, but stocked fish may also be affected. During fish entrainment surveys at two pump intakes on the Macquarie River, New South Wales, a noticeable increase of entrained juvenile Murray Cod (Maccullochella peelii) was observed. DNA parentage analysis confirmed that a large proportion of these fish were linked to nearby fish restocking events. At both pump intakes, genetic analysis confirmed that at least 70% and 17% of the individuals sampled were stocked fish. This equated to up to 3% of the fish that were stocked – most of which were entrained less than 24 h after their release. Given the large number of unscreened irrigation pumps in this reach of river, and more broadly throughout the Murray–Darling Basin, fish losses at pump intakes have the potential to remove large numbers of stocked fish from the river where they are released to support native fish recovery and boost recreational fishing opportunities. The use of fish‐protection screens at pump intakes may be a suitable solution to reduce the number of fish entrained and thus increase the survival of recently stocked fish in the rivers.

Estimating the costs of managed aquifer recharge under uncertainty with examples for town water supply in regional Australia

HighlightsCost distribution curves for well injection and infiltration basin recharge schemes.Probabilistic, time-varying, coupled water balance and net present value modelling.Disaggregated capital and operating expenses and global sensitivity analyses.Examples for increasing regional area town water security in Australia’s Murray Darling Basin.

Community-Centred Environmental Discourse: Redefining Water Management in the Murray Darling Basin, Australia

Community-Centred Environmental Discourse: Redefining Water Management in the Murray Darling Basin, Australia

Changes in moisture sources contributed to the onset and development of the 2017-2019 southeast Australian drought

In 2017-2019 southeast Australia experienced one of its most severe droughts since 1900. Rainfall over the region encompassing the Murray-Darling Basin was consistently below average for three consecutive cool seasons, an unprecedented event on record. A strong positive Indian Ocean Dipole event has been previously suggested to have intensified the conditions of the drought in 2019, however the state of the climate drivers cannot fully explain the onset and development of this drought. In this study, we adopt a different approach to investigate processes other than remote climate drivers that may have triggered the drought. Using a Lagrangian model to identify moisture sources to the Murray Darling Basin, we show that local processes were crucial in explaining the onset and development of the drought. We identify the oceanic and terrestrial sources of atmospheric moisture over the Murray Darling Basin and show for the first time a significant decline in rainfall moisture supply from the Tasman Sea in 2017 and 2018. We further show that anomalous atmospheric circulation transported the expected moisture northward toward the Maritime Continent. Our results provide an explanation for the moisture and rainfall deficit that caused the 2017-19 southeast Australian drought. Understanding the processes that led to the 2017-2019 drought is an important step towards improved predictions and planning for future multi-year droughts in Australia.

Diel patterns of habitat use and movement by juvenile and subadult trout cod (Maccullochella macquariensis) in a regulated lowland river

Improved knowledge of habitat use and movements is needed to support recovery of threatened riverine fish species. The trout cod (Maccullochella macquariensis) is a nationally threatened fish species endemic to rivers of the southern Murray–Darling Basin (MDB), Australia. This study investigated diurnal and nocturnal habitat use and movements of trout cod in the Goulburn River, using radio-telemetry. Trout cod typically occupied small reaches (<300 m) of stream during the late spring–summer study period. Larger-scale movements (mostly home-range shifts) and movements onto inundated riparian habitats also occurred during a period of high discharge. Trout cod occupied deeper water further from the bank during the day and shallower water closer to the bank during the night and used areas with slower velocities more than was their availability, particularly during the earlier hours of the day. They also made extensive use of in-stream cover (i.e. wood). Our information on diel habitat use provides a platform to guide informed management (e.g. availability of preferred habitats under different river-discharge scenarios) to improve trout cod population sustainability.

Assessing stakeholder structure in water governance in the Murray-Darling Basin, a public submission perspective

Transformation from top-down government to collaborative governance for natural resources requires broadening the scope of stakeholders involved. However, the systemic identification and assessment of stakeholder engagement remains a challenge. This paper develops a network-based framework for assessing stakeholder engagement in natural resources governance. The framework proposed five system-level metrics: inclusivity, cohesion, centralization, efficiency, and brokerage, as well as three node-level metrics: dominators, brokers, and communicators. By using public submission data on four government policy initiatives each reflecting a major component of the Murray-Darling Basin Plan, this study assessed the structural aspects of stakeholder engagement relevant to water resource management in the Murray-Darling Basin following legislative reforms in 2007. Findings suggested that current stakeholder engagement structures are neither balanced, nor have adequate maturity to develop a governance approach to resolve issues within the Basin. High variability between patterns of involvement in submissions to key policy initiatives indicated there were haphazard aggregations of public comments and the top-down approach to water management is still dominant. The framework developed in this paper offers a structural and systemic perspective for re-configuring stakeholder engagement networks for improving collaborative governance.

Combining Sentinel 1, Sentinel 2 and MODIS data for major winter crop type classification over the Murray Darling Basin in Australia

Crop type classification is an essential task in agriculture that has been studied widely since the emergence of remote sensing technologies. Accurate crop mapping can help assist decision-making related to storage, marketing, and other production tasks. This study has designed robust crop classification models to classify two major crop types (cereals and canola) in the Murray Darling Basin (MDB) in Australia. These models combined Sentinel 1 and 2 and Moderate Resolution Imaging Spectroradiometer (MODIS) data. Three methods were applied to test classification quality: the holdout method, leave-one-season-out cross-validation (LOSOCV), and leave-one-cluster-out-cross-validation (LOCOCV). The holdout method evaluated the model's performance on data representing the entire population. The LOSOCV method was used to test the model's ability to extrapolate over time (unseen data from new seasons), and the LOCOCV method was used to test the ability to extrapolate over space (data from a new site). Crop type labelled data (n = 193 for cereals and n = 113 for canola) were extracted from high-resolution yield maps derived from grain yield monitors mounted on harvesters, and this was used to train and validate the classification models. The results showed that the holdout validation approach achieved the highest accuracy (overall and Kappa scores >0.98), but this might be caused by spatial autocorrelation of the sampling strategy implemented, which leads to an overoptimistic scenario. The overall accuracies and Kappa scores achieved from the LOSOCV method varied depending upon the difference in crop phenology from season to season, with overall accuracy ranging from 0.70 to 0.92 and Kappa scores from 0.61 to 0.90. The overall accuracies and Kappa scores for the LOCOCV ranged from 0.87 to 0.99 and 0.84 to 0.98, respectively. The gross primary productivity (GPP) and the chlorophyll red edge index (CIr) were the most important features across the three models. The outputs of this research can potentially complement models that require crop type information, such as carbon cycling and crop yield models.

Living with hypoxia: Residence and site fidelity by golden perch (Macquaria ambigua) in habitats affected by methane seeps and chronic hypoxia

Abstract We conducted an acoustic telemetry study of native golden perch (Macquaria ambigua) to examine movement behaviour in areas affected by methane seeps and hypoxia in the intermittent Condamine River, Murray‐Darling Basin (MDB), Australia. Fish were collected during periods of no flow and hypoxia (dissolved oxygen [DO] <1 mg/L). Despite these conditions, 38 of 43 fish tagged with acoustic transmitters were detected for >3 months post‐tagging in the study reach and 27 fish were being detected after 14 months. During periods of elevated river flow and relatively high DO, 30 fish moved away from their original tagging locations, with three undertaking movements (>7 km) outside the study reach and not returning. Generalised additive mixed models showed a significant increase in the probability of movement as soon as flow commenced and when water temperatures exceeded 19°C. As flows receded, most fish that had moved exhibited accurate homing behaviour to their original tagging location. The patterns of movement and site fidelity exhibited by golden perch correspond with previous studies of the species in intermittent rivers not affected by methane seeps and severe hypoxia, suggesting that the methane seeps and hypoxia did not inhibit fish movement nor render the affected habitats unsuitable for habitation. Golden perch can survive and remain active in water with much lower DO (<1 mg/L) than previously described for large‐bodied native fishes in the MDB. However, fish condition in the study reach was slightly lower than other regions of the MDB, providing preliminary evidence that fish residing in habitats affected by chronic hypoxia and methane seepage may experience sub‐lethal stress. Our results demonstrate the importance of field‐based data on the behavioural and physiological responses of fish to chronic hypoxia and methane exposure to guide appropriate management responses.

Potential for historically unprecedented Australian droughts from natural variability and climate change

Abstract. In drought-prone Australia, multi-year droughts have detrimental impacts on both the natural environment and human societies. For responsible water management, we need a thorough understanding of the full range of variability in multi-year droughts and how this might change in a warming world. But research into the long-term frequency, persistence, and severity of Australian droughts is limited. This is partly due to the length of the observational record, which is short relative to the timescales of hydroclimatic variability and hence may not capture the range of possible variability. Using simulations of Australian precipitation over the full past millennium (850–2000), we characterise the nature of multi-year meteorological droughts across Australia and include a particular focus on the Murray–Darling Basin (MDB), the largest agricultural region in Australia. We find that simulated Australian droughts in the 20th century (1900–2000) are within the bounds of pre-industrial natural variability in terms of drought intensity, severity, and frequency. A tendency for droughts to last longer in southwestern and eastern Australia (including the MDB) in the 20th century, compared with the pre-industrial period, suggests an emerging anthropogenic influence, consistent with projected rainfall changes in these regions. Large volcanic eruptions tend to promote drought-free intervals in the MDB. Model simulations of droughts over the last millennium suggest that future droughts across Australia could be much longer than what was experienced in the 20th century, even without any human influence. With the addition of anthropogenic climate change, which favours drought conditions across much of southern Australia due to reduced cool-season rainfall, it is likely that future droughts in Australia will exceed recent historical experience.

Water Market Development in the Yellow River Basin: Challenges and Opportunities

Water market development in the Yellow River Basin (YRB) unfolds new opportunities for alleviating water scarcity and improving water productivity. However, the further development of an effective water market in the basin faces challenges such as unclear water rights, regulatory deficiencies, market deficiencies, and insufficient compensation to third-parties, among others. Studying water market development in Western countries provides useful insights for addressing similar challenges, thus providing useful case studies despite the different cultural, economic, institutional, and political settings. This paper investigates water markets in the Murray–Darling Basin in Australia, the western United States, and Chile to synthesize cases of water market development that could potentially contribute to overcoming the challenges encountered in the YRB. After analyzing these cases, recommendations are made for enhancing the YRB’s water market development from the perspectives of water rights systems, as well as the roles of the government and market, legal system, and third-party effects.

Options on temporary water allocation rights and their pricing

AbstractThis paper presents a methodology for defining the spot price of temporary water allocation rights for trading zones within the water market in the southern Murray–Darling Basin situated in Australia. The historical spot price is then used to calibrate a stochastic process depicting the dynamics of the water price, allowing the computation of prices of options on the underlying water price with the aim of producing reference prices to catalyse an options trading market. The most suitable stochastic model representing the water price dynamics is selected through comparing the option prices generated from four different models. Using the selected stochastic model, the most liquid trading zone in the Murray–Darling Basin water market (Zone 7) is used to demonstrate how the methodologies developed in the paper are used to calibrate the log‐mean stochastic model representing the stochastic spot price dynamics and compute prices for call and put options on the underlying water spot prices. Sensitivities of the water options prices to market input data can be calculated from the formulae provided in the paper. The results presented in this work can serve as a reference tool by industry practitioners and the farming community in using options for effective risk management of water resources.

Biology, distribution and conservation of a dwarf-group crayfish, Euastacus spinichelatus Morgan, 1997 (Decapoda: Astacidea: Parastacidae), a freshwater crayfish from the Great Dividing Range, New South Wales, Australia

Abstract We present the outcomes of two conservation initiatives, namely ‘The Australian Crayfish’ and ‘Saving the Spinys’ projects, which have substantially contributed to enhancing our understanding of E. spinichelatus concerning its distribution, habitat, biology, and conservation status. We extend the range of E. spinichelatus to encompass the headwater reaches of the Namoi River within the Murray-Darling Basin. The use of molecular taxonomy analyses identified divergent lineages that acted to remove the southeastern tributaries of the Hastings River and the most western tributary of the Manning River from the range of E. spinichelatus. The species has suffered significant population declines in recent years, with it appearing to be highly susceptible to anthropogenic changes, drought and/or high-severity bushfires. Results advocate for the classification of E. spinichelatus as an endangered species, recognizing its distinctive ecological niche and its status as a climate refugee, aiming to protect this rare species from anthropogenic and climate-related challenges. We also present a taxonomic key differentiating E. spinichelatus from other members of Parastacidae in the region.

The Australian public’s preferences for further environmental and cultural water recovery options in the Murray-Darling Basin

The Murray-Darling Basin (MDB) Plan in Australia legislated in 2012 represents the largest recovery of water, from consumptive use to environmental use in the world – with the aim of restoring rivers and ecosystems back to health. To date, although billions of dollars have been spent, the Plan’s water recovery targets have not been achieved and will not meet their original target dates for full recovery, with governments needing to continue to make difficult water policy choices and trade-offs. This study explores a survey of Australian public preferences for five different water reallocation options in the MDB (and methods to be used for recovery) and identifies individual characteristics associated with various policy options. Almost a quarter of those surveyed did not support further water recovery; 17 % favoured recovering water to current goals only; 22 % favoured recovering environmental water beyond current goals; while 38 % favoured recovering both environmental and cultural water beyond current goals. For those wanting further recovery, a third preferred using irrigation infrastructure subsidies as the main method, while the majority favoured buying water directly back from irrigators (either through voluntary buyback or compulsory acquisition). Trust levels, location, age, climate change perception and gender all played a part in influencing respondent preferences for various water recovery options.

A misconstrued alien: the freshwater turtle Emydura macquarii in the Greater Sydney region

ABSTRACT Many freshwater turtle species have spread beyond their natural distributions through human agency, but introduced populations can be difficult to differentiate from natural ones. The occurrence of an Australian freshwater turtle, Emydura macquarii, in the Greater Sydney region, Australia’s most populous urban and peri-urban area, has alternatively been assumed to be natural or deduced to be due to anthropogenic introduction. I apply multiple lines of evidence to show that the occurrence of E. macquarii in the Sydney region is not natural and that the species has proliferated and spread there much more than the notoriously invasive red-eared slider turtle, Trachemys scripta elegans. The E. macquarii population of the Sydney region is highly diverse morphologically, with individuals variously resembling E. macquarii from Queensland, the north coast of New South Wales, and the Murray–Darling Basin. Better understanding is needed of the population genetics of E. macquarii in the Sydney region, the interactions among the region’s native and introduced turtles, and the impacts of E. macquarii on biota other than turtles.

Water courses and discourses: A media content analysis of environmental water reporting in Australia

This study presents the findings of a media content analysis (n=303) of articles discussing environmental water (water allocated to the environment in freshwater systems) in the Murray-Darling Basin in Australia across 20 years (2001 – 2021). The aim of the study was to determine the disposition of the articles, the actors (voices) invoked within them, as well as the topics they discuss in relation to environmental water, with a particular emphasis on understanding the representation and power dynamics prevalent in media discourse. The analysis highlighted that negative portrayals of environmental water occurred more often than those that were positive in nature. This led to a lack of balance in representation in heralding certain views, such as pro environmental, over others, such an economic arguments. Notably, Indigenous voices were given almost no representation across the analysed articles, while settler colonial voices such as Irrigators and Irrigator Lobby Groups were provided with a disproportionately larger share of discussion, driving the anti-environmental water disposition. This is notable as it serves to sway debate towards certain views and conceptualisations such as an economic valuing of environmental water. As such, environmental water is often discussed in the context of the economy and livelihoods of communities. There is a notable absence of discussions of climate change and cultural water in the debate, with zero mentions of either across all surveyed articles. This is surprising considering climate change is expected to reduce water availability across the basin by 20% in years to come. Water discussed as a commodity was regularly featured in discussion, which lends itself to understanding the wider policy debate nestled in neoliberal framings, rather than other valuations of water, such as environmentalist or Indigenous understandings. This has wider implications for other countries that are considering policy options for allocating environmental water and how a market-driven approach to water allocation serves to sway public discourse.

Changes in Weather Systems during Anomalously Wet and Dry Years in Southeastern Australia

Abstract This study focuses on the rainfall-producing weather systems in the southern Murray–Darling Basin (MDB), Australia. These weather systems are divided into objects: cyclones, fronts, anticyclones, warm conveyor belt (WCB) inflows, WCB ascents, potential vorticity (PV) streamers, and cutoff lows. We investigate the changes in the frequency, amplitude, and relative position of these objects as the daily and seasonal rainfall change. Days on which the rainfall is heavy, especially in winter, are characterized by more PV streamers, cutoff lows, cyclones, fronts, and WCBs in the region. In contrast, dry days are characterized by more anticyclones over southeastern Australia in winter and summer. The effect of upper-level weather objects (PV streamers and cutoff lows) on lower-level objects, and their importance in producing rainfall, is quantified using the quasigeostrophic ω equation and separating the vertical motion into that induced by the upper and lower levels. On heavy rainfall days in winter, PV streamers and cutoff lows force strong upward motion in the lower troposphere, promoting cyclogenesis at lower levels, forcing ascent in the WCBs, and producing rain downstream of the southern MDB. Lower-level ascent forced by upper-level objects is important for the development of heavy rainfall in both seasons, although particularly in winter. Rainfall is attributed to individual objects. PV streamers and WCBs contribute most to the winter and summer rainfall, respectively. The difference in rainfall between anomalously wet and dry years can be explained in winter by the changes in the rainfall associated with PV streamers, whereas in summer it is mostly due to a reduction in the rainfall associated with WCBs. Significance Statement The aim of the present study is to better understand how synoptic-scale weather systems differ in southeastern Australia in dry and wet periods, by considering a wide range of weather systems. We found weather systems are more closely aligned in the vertical on heavy rainfall days, and the majority of rainfall in this region is associated with warm conveyor belts. These results point to warm conveyor belts being an important, but not well recognized, contributor to rainfall in this region. Future work may investigate the roles of the various modes of variability and climate change in modulating warm conveyor belts and hence the regional rainfall variability in Australia.

An environmental flow to an ephemeral creek increases the input of carbon and nutrients to a downstream receiving river

Although intermittent and ephemeral rivers lack surface flow for part of the year, they provide vital refuges for biota in otherwise dry semi-arid and arid landscapes. The hydrology of many such rivers has been altered due to river regulation and climate change. Environmental flows can be delivered to address the negative impacts of regulated flows, however there is limited knowledge of how dry ephemeral ecosystems respond following environmental flows. This study examined changes in water quality of the ephemeral Thule Creek in the southern Murray-Darling Basin, Australia, following delivery of environmental water from an irrigation canal. We also examined how the environmental flow influenced water quality of Wakool River that receives inflows from Thule Creek. Six sites in Thule Creek, three in Wakool River, and one in Yarraman irrigation channel (source water) were monitored for dissolved organic carbon (DOC), nutrients and dissolved oxygen (DO) once per week over 15 weeks from October 2019 to January 2020. The environmental flow resulted in high DOC concentrations (4.4–76 mg/L). Although low DO levels at sites in Thule Creek were recorded on some dates below the threshold for fish stress (< 4 mg/L) there were no fish kills observed during the environmental flow. The carbon-rich and nutrient-rich water (DOC >10 mg/L, total phosphorus up to 94 μg/L, total nitrogen up to 1,125 μg/L) was detected in the Wakool River downstream of Thule Creek confluence compared to the Wakool River upstream of Thule Creek confluence (DOC 6.6 mg/L, total phosphorus up to 64 μg/L, total nitrogen up to 805 μg/L) during the period when the environmental flow in Thule Creek was connected with the Wakool River. This research provides an example of how irrigation canal networks can be used to deliver environmental water to an ephemeral river to maintain refuges and contribute to the productivity of a receiving river further downstream. Careful management of the timing, volume and duration of environmental flows in arid or semi-arid landscapes is needed to avoid the development of poor water quality during, or following, the delivery of environmental water.

A method to predict connectivity for nomadic waterbird species from tracking data

ContextNomadic waterbird species move erratically, which makes it difficult to predict site use and connectivity over time. This is particularly pertinent for long-distance movements, during which birds may move between sites hundreds to thousands of kilometres apart.ObjectivesThis study aimed to understand how landscape and weather influence long-distance waterbird movements, to predict the probability of connectivity between locations and forecast short-term movements for a nomadic species, the straw-necked ibis (Threskiornis spinicollis) in Australia’s Murray–Darling basin.MethodsWe used 3.5 years of satellite tracking data together with high-resolution landscape and weather variables to model the expected distance travelled under environmental scenarios for long-distance movements. We generated least-cost paths between locations of interest and simulated the probability that birds could exceed the least cost-distance as a measure of connectivity. We also generated short-term forecasts (1–3 days; conditional on departure) of the probability of bird occurrence at a location given the expected environmental conditions.ResultsOur results suggested that wind is the dominant predictor of distance travelled during long-distance movements, with significant but smaller effects from month. Birds travelled further when wind benefit was higher and during summer. Further work is required to validate our forecasts of bird positions over short time periods.ConclusionsOur method infers the predictors of poorly understood movements of nomadic birds during flight. Understanding how partial migrants use landscapes at large scales will help to protect birds and the landscapes where they live.