River Murray Floodplain Research Articles

An archaeological example of Aboriginal management of a hydro-ecological system in the Murray River valley, South Australia

Context A rare archaeological example of Aboriginal water management in a Murray River floodplain upstream of Renmark is described and contextualised. Aims Historical accounts, archaeological descriptions and hydrological modelling are used to propose a likely function of the site. Methods The site was documented through archaeological field recording, a digital elevation model (DEM) developed through a real-time kinematic (RTK) survey and flood inundation modelling (FIM), and is interpreted through a review of archival and documentary sources. Key results The site represents one of only a few extant physical examples of Aboriginal water management in the Riverland and greater Murray–Darling Basin. Conclusions Our assessment indicates that Aboriginal people had excavated an artifical channel within the Calperum floodplain in order to manipulate natural water connectivity, most likely as part of a fish trap or weir structure. Implications The site builds an appreciation of the complexity of Aboriginal land practices and supports the impression gained though historical accounts of a curated and managed riverscape.

Potential drivers of common brushtail possum (

Australia’s terrestrial mammalian fauna have experienced severe declines since European settlement. On the Murray–Darling floodplain in south-eastern Australia, common brushtail possums (Trichosurus vulpecula, ‘possums’), have contracted to riparian zones. Although an important possum refuge, little is known about possum population dynamics here. We examined possum population dynamics and potential drivers across two decades on the Murray River floodplain at Calperum Station. We related possum density to satellite derived fractional cover, (a measure of the proportion of green, non-green and bare ground cover), and contextualised these findings using tree condition and grazing pressure datasets. Possum surveys were conducted between 1998 and 2019 in riparian and non-riparian habitats and density was modelled in relation to fractional cover values of green, non-green, and bare ground. Possum density fluctuated between 1998 and 2008 but in 2018 and 2019, possums were undetectable. Possum density was negatively associated with bare ground and positively associated with non-green. Overgrazing by kangaroos likely reduced vegetation cover and diversity and contributed to possum decline, via a reduction in possum food resources and increased exposure to predation. Inconsistent monitoring meant that the population decline was not detected until after it had occurred, and management interventions were not triggered, highlighting the dilemma of allocating scarce monitoring resources.

Aboriginal earth mounds of the Calperum Floodplain (Murray Darling Basin, South Australia): New radiocarbon dates, sediment analyses and syntheses, and implications for behavioural change

This paper presents the results of an archaeological investigation into anthropogenic earth (oven) mounds located on the Murray River floodplain at Calperum Station in the Renmark region of South Australia. Six mounds were excavated and their contents examined. Sediment analyses were also conducted to assess magnetic susceptibility, grain size and loss on ignition. Radiocarbon age estimates were obtained on shell and charcoal. Mound contents primarily included anthropogenically burnt clay (heat retainers), charcoal, fragments of mussel shell as well as very minor quantities of other faunal material and stone artefacts (which were consistent with previous lithic assessments for the region). The radiocarbon age determinations from 15 samples indicate that mounds were formed by Aboriginal people on the Calperum floodplain from at least 3981–3723 cal BP and utilised up to the time of European invasion. The very minimal amount of faunal remains (other than mussel shell), artefacts and a general lack of other material evidence apart from clay heat retainers, confirms that these features were single purpose and not used as living areas. Sediment analyses and radiocarbon dates indicate a high degree of homogeneity within mounds but provide insights into an economic transition on the Calperum floodplain, at around 4000 cal BP involving a food-production procurement strategy based on heat retainer technology and the exploitation of emergent macrophytes.

Constraining organic matter composition and dynamics as a dominant driver of hypoxic blackwater risk during river Murray floodplain inundation

AbstractThe ecology of floodplain ecosystems evolved according to the historical frequency and extent of inundation. In many dryland rivers, inundation frequency has reduced due to regulation, competition for water resources and climate change. In some rivers infrastructure has been constructed to enable temporary rises in water level and more frequent floodplain inundation, delivering environmental water to ecosystems that are dependent on surface water. During such events, the release of dissolved organic carbon (DOC) from inundated plant material may result in depletion of dissolved oxygen (DO). If the rate of DO depletion exceeds re‐aeration, hypoxic conditions can occur. Models have been developed to represent these processes, however, there is a wide range of chemical and biological interactions, and hence model parameters, involved. The aim of this research was: (1) identify the dominant parameters through sensitivity analysis, (2) design and implement a field monitoring program to quantify the inherent variability in those parameters, and (3) translate that input variability into the modelled DO, ultimately to support risk management decisions when planning delivery of environmental water. The results indicated that the mass of organic matter on a floodplain had the greatest impact on the modelled DO concentrations. Based on the field monitoring results, the steady state load of organic matter, that is, when the accumulation and decay rates are equal, was estimated, and vegetation mapping used to apply the field monitoring results across the floodplain for a 206 km reach of river of the River Murray, Australia. The model results from multiple, cumulative, operations identified one particular high‐risk operational site. The results are useful to prioritize monitoring effort to focus on the most sensitive model parameters and indicate that the likelihood of hypoxic conditions can be reduced through slower rates of inundation and timing events to coincide with periods with lower water temperature. The methodology developed can be transferred to other sites where hypoxic conditions are a potential outcome associated with delivery of environmental water.

Correction to: Phosphorus speciation and release from different plant litters on a River Murray (Australia) floodplain

Correction to: Phosphorus speciation and release from different plant litters on a River Murray (Australia) floodplain

Phosphorus speciation and release from different plant litters on a River Murray (Australia) floodplain

Phosphorus speciation and release from different plant litters on a River Murray (Australia) floodplain

Aboriginal heritage as ecological proxy in south-eastern Australia: a Barapa wetland village

ABSTRACT Aboriginal archaeology has a central role to play among the myriad government agencies and professional disciplines involved in land and water management of the Murray River Basin in south-eastern Australia. In this study, we examine managed water flows against the archaeological record which provides secure evidence of how people lived at the Murray River floodplain wetlands before European colonisation. Seasonal residential patterns and economic activities of large populations have been reconstructed using archaeological, environmental, and hydrological information. The result is a picture of people living in large groupings – villages and hamlets – around water bodies that we suggest are ecological ‘hot spots’ within the forest. In identifying the preferred locations of village sites, we present the case for modification of environmental water delivery from large area forest flooding to targeted smaller water bodies that form ecological hot spots throughout the river floodplain landscape. Traditional Aboriginal land use in the form of the distribution of Aboriginal sites can act as an environmental proxy to inform heritage, land and water management policy and practices that seek to restore the health of the Murray River.

‘Branching’ with complex coarse woody debris reduces herbivory on recovering erosion scalds

SummaryCoarse woody debris (CWD) has many benefits in restoration, including protecting seedlings from herbivory, and it is often reintroduced where CWD is depauperate. At Calperum Station on the Murray River floodplain, artificially applied CWD (‘branching’) is being trialled to restore erosion scalds. At two erosion scalds, we applied 900 m2 of branching and created a 900 m2 branching‐free control. We predicted that branching would protect seedlings from browsing by mammalian herbivores. We planted Nitre Goosefoot (Chenopodium nitrariaceum) seedlings in each treatment and measured the number of terminal ends affected by herbivory and plant height for 8 weeks. Branching reduced the number of terminal ends affected by herbivory by ~80% and plant height loss by ~60%. Remote cameras detected some browsing by kangaroos, the most abundant herbivores on the Calperum floodplain, although cameras were too few to directly observe much of the browsing that occurred. We did not detect an effect of site browsing pressure on overall herbivory or the effectiveness of the branching. Despite the small sample size, our results suggest that branching can effectively reduce herbivory. It is likely that the effectiveness of branching in reducing herbivory is conditional on a range of factors, such as browsing pressure (i.e. scat density), so a large‐scale trial is required to clarify the role branching has on reducing herbivory in relation to these complex interactions.

Restoring Murray River floodplain wetlands: Does the sediment record inform on watering regime?

AbstractThe floodplain wetlands of the southern Murray Darling Basin (MDB) have been subject to the impacts of catchment and water resource development for more than a century. Their current degraded state is attributed to the regulation of the rivers and abstraction of water volume for irrigation. The MDB Plan is to return at least 2,750 Gl of mean annual flow to the system to restore the condition of waterways. Considerable recent investment in infrastructure enables water to be released into the basin's floodplain wetlands. The proposed watering regime is underpinned by modelling that suggests that, before regulation, overbank flows would have occurred regularly as discharge peaked in winter and spring. Sediment cores have been extracted from over 50 floodplain wetlands of the southern Murray Basin. Those from several, large meander wavelength billabongs extend for 1,000–5,000 years suggesting that these sites were permanently inundated over that time. Others extend to ~200 years and are presumed not to have accumulated sediment until more recently. The records of most wetlands, however, only extend to the onset of river regulation in the 1920s, suggesting that before then they were not inundated for sufficient duration for net accumulation to occur. Preserved diatoms suggest that the shallow, plant‐dominated wetlands of the past have transitioned to deep, turbid water systems today. As rivers are identified as a source of sediment to wetlands, less regular inundation, rather than more, is a viable option in restoring the ecological function of these floodplain wetlands and in slowing sediment infill.

A huge diversity of metopids (Ciliophora, Armophorea) in soil from the Murray River floodplain, Australia. III. Morphology, ontogenesis and conjugation of Metopus boletus nov. spec., with implications for the phylogeny of the SAL supercluster

The morphology, ontogenesis, conjugation, and phylogenetic position of Metopus boletus nov. spec. were studied using live observation, various silver impregnation methods, scanning electron microscopy, morphometry, and the 18S rRNA gene sequence. The new species is outstanding in having a mushroom-like appearance; a globular to broadly ellipsoid macronucleus in anterior body half; 5–10 elongated caudal cilia; 4–6 dikinetids curved rightwards in the anterior portion of the first postoral kinety; and an adoral zone composed of an average of 28 small polykinetids. Ontogenesis of M. boletus follows the metopid mode and the species-specific vegetative morphology is obtained after division. Its conjugation is temporary, isogamic and the partners unite ventral-to-dorsal, forming strongly arched to almost rod-like pairs, which indicates a heteropolar arrangement. There are only two maturation divisions and a single synkaryon division in exconjugants. The conjugation data corroborate a sister group relationship of the classes Armophorea and Litostomatea within the SAL (Spirotrichea + Armophorea + Litostomatea) supercluster in that the partners unite ventral-to-dorsal and the main body axes are antiparallel. On the other hand, the last common ancestor of the spirotricheans very likely had a ventral-to-ventral and homopolar conjugation mode with the main body axes oriented in parallel.

A huge diversity of metopids (Ciliophora, Armophorea) in soil from the Murray River floodplain, Australia. I. Description of five new species and redescription of Metopus setosus Kahl, 1927

Six metopid ciliates from soil of the Murray River floodplain in Australia were studied using live observation, various silver impregnation methods, scanning electron microscopy, and multivariate statistics. One of the species is affiliated with M. setosus while the others represent new taxa. Metopus filum nov. spec. is distinguished from most congeners by the slender body, the absence of cortical granules, and the low number of ciliary rows and adoral polykinetids. Metopus palaeformides nov. spec. most resembles Heterometopus palaeformis (Kahl, 1927) Foissner, 2016b but they can be distinguished by body size, the number of adoral polykinetids, and the oral area pattern. Metopus murrayensis nov. spec. is outstanding in having a globular macronucleus surrounded by innumerable refractive granules and a conspicuously thick preoral dome. Metopus rex nov. spec. and M. magnus nov. spec. are easily distinguished from most congeners by their large body size and the shape of the macronucleus. Moreover, M. rex displays up to 30μm long endosymbiotic bacteria while the micronucleus of M. magnus is uniquely situated in a small macronuclear concavity. Multivariate statistics corroborates the distinctness of these six metopid populations.

Return of the lignum dead: Resilience of an arid floodplain shrub to drought

In semi-arid regions, woody floodplain plants have developed methods of tolerance to both flooding and drought. Understanding the limits of tolerance to drought is critical to the efforts of restoring these communities. In Australia, Tangled Lignum (Duma florulenta (Meisn.) T. M. Schust) is an ecologically significant floodplain shrub that dominates large areas of the Murray–Darling and Lake Eyre Basins. This study investigates the resilience of lignum plants to dry periods by examining the capacity of plants to regenerate from dormancy. In particular, this study sought to test the hypothesis that lignum regeneration is influenced by increasing duration of dormancy. Variability in regeneration response across the study period was also looked at in relation to regional rainfall and flow. Lignum plants were surveyed at 12 sites on the Murray River floodplain in north-western Victoria. Sites were monitored seven times between 2006–07 and 2012–13. This study found that although lignum can regenerate from dormancy, regeneration is not guaranteed and the likelihood of successful regeneration varies among locations and diminishes with increasing length of dormancy. Lignum communities should be managed to maintain condition and resilience to drought in order to give lignum plants the greatest chance of regeneration success.

Morphology and ontogenesis of Stylonychia (Metastylonychia) nodulinucleata nov. subgen. (Ciliophora, Hypotricha) from Australia

Using standard methods, we describe the morphology and ontogenesis of a possibly very rare ciliate, Stylonychia (Metastylonychia) nodulinucleata nov. subgen (basionym: Stylonychia nodulinucleataShi and Li, 1993), isolated from soil of the Murray River floodplain in Australia. Further, we provide an English translation of the Chinese original description. Whether the Australian population is conspecific with the Chinese Stylonychia nodulinucleata requires a careful redescription of the latter. The new subgenus is characterized by a moniliform macronuclear strand and an ontogenetic feature, viz., that all cirri remain intact during anlagen formation. The moniliform macronuclear strand and the curved dorsal kineties resemble the stylonychid genus Coniculostomum. The species is easily recognized by the large size of the body and oral apparatus, the moniliform macronucleus, and the enormous caudal cirri reaching half of body length. Very likely, Stylonychia (Metastylonychia) nodulinucleata has a restricted distribution.

Palaeoecological evidence for sustained change in a shallow Murray River (Australia) floodplain lake: regime shift or press response?

Paleolimnological techniques can reveal long-term perturbations and associated stable state transitions of lake ecosystems. However, such transitions are difficult to predict since changes to lake ecosystems can be abrupt or gradual. This study examined whether there were past transitions in the ecological regime of Kings Billabong, a shallow River Murray wetland in southeast Australia. A 94-cm-long core, covering c. 90 years of age, was analysed at 1 cm resolution for subfossil cladocerans, diatoms and other proxies. Prior to river regulation (c. 1930), the littoral to planktonic ratios of cladocerans and diatoms, and bulk sediment δ13C values were high, while the period from c. 1930 to c. 1970 experienced considerable changes to the wetland ecosystem. The abrupt nature of changes of planktonic cladocerans and diatoms, particularly after the onset of river regulation (1930s), was triggered by inundation, high rates of sedimentation and shifts in bulk sediment δ15N values. However, the transition of a once littoral-dominated community, to one favouring an increasingly turbid, plankton-dominated trophic condition following river regulation was relatively slow and lasted for decades. The progression to a new regime was likely delayed by the partial recovery of submerged plant communities and related internal dynamics.

Tracking a century of change in trophic structure and dynamics in a floodplain wetland: integrating palaeoecological and palaeoisotopic evidence

Summary The palaeoecological assessment, and the use of stable isotopes of carbon in subfossils of herbivores and omnivores, represents a novel approach to understand transitions in past food‐web structure and the dynamics of lake ecosystems in response to natural perturbations and human impacts. Combined with records of subfossil assemblages of cladocerans and chironomids, it may be possible to decipher whether changes are attributable to external forces or internally derived system shifts. A sediment record taken from the shallow (2.3 m depth) Kings Billabong in the River Murray floodplain (Australia) was analysed to explore changes in trophic dynamics over the past century. The palaeoecological assessment revealed that littoral assemblages of cladocerans and benthic diatoms were gradually replaced by planktonic (planktonic and facultative planktonic) assemblages after river regulation in the 1920s. The stable isotopic composition of carbon (δ13C), derived from chironomid head capsules, was relatively constant down‐core, ranging between −26.1‰ and −24.0‰, and coincided largely with the δ13C of bulk sediment samples (−25.6‰ to −22.0‰). The δ13C values of pelagic (Daphnia) and ubiquitous (Bosmina, Alona) cladocerans, however, varied markedly, with that for Daphnia between −29.8‰ (10–20 cm) and −23.2‰ (60–70 cm), and for ubiquitous cladocerans, between −29.4‰ (20–30 cm) and −24.5‰ (80–70 cm). The temporal changes in the δ13C values of cladocerans also suggest a gradual transition from a macrophyte‐dominated state to a phytoplankton‐dominated state after river regulation and further indicate changes in the horizontal migration behaviour of Daphnia depending on macrophyte abundance and predation risk. Our study demonstrates the potential of reconstructing, more precisely, the trophic dynamics of large river floodplain lakes and their ecological resilience by combining subfossil analyses with stable isotope analyses of selected subfossil groups.

Floodplain vegetation of the River Murray in 1987–1988: an important pre-drought benchmark for subsequent studies.

Floodplain vegetation of the River Murray in 1987–1988: an important pre-drought benchmark for subsequent studies.

Ecological response of Eucalyptus camaldulensis (river red gum) to extended drought and flooding along the River Murray, South Australia (1997–2011) and implications for environmental flow management

Riparian forest and woodlands of the lower River Murray floodplain are exhibiting deteriorating health as a result of anthropogenic alterations to flow regimes and south-eastern Australia’s long-term ‘Millennium Drought’ from 1997 to 2009. Extensive flooding in 2010/2011 brought the drought to an end, providing an opportunity to monitor ecological floodplain recovery. The relationship between flooding and lateral recharge and condition of the dominant riparian tree species, Eucalyptus camaldulensis, was determined between 2007 and 2011 using the Landsat (LTM5) Normalised Difference Vegetation Index (NDVI). Linking the river hydrograph with the River Murray Floodplain Inundation Model (RiM-FIM) allowed exploration of the relationship between inundation duration and E. camaldulensis water requirements. Results indicate lateral bank recharge is an important mechanism in the maintenance of vegetation condition along the River Murray channel. Higher in-channel irrigation water delivery during summer months was identified as critical to survival of trees adjacent to the channel during the drought. The research suggests that weir pool manipulation to create in-channel flood pulses will aid E. camaldulensis maintenance. Furthermore, release of environmental flows once every 3 to 5 years to create bank-full flow or preferably overbank flows, will increase hydrological connectivity between river banks, wetlands and riparian zones, providing positive ecological benefits to E. camaldulensis and other floodplain and aquatic ecological assets.

Using AEM data as part of an integrated assessment of the salinity hazard and risk to Gunbower State Forest and the River Murray floodplain in the Gunbower Island Barr Creek reach of the Murray River, SE Australia

In 2007 the Australian Government funded an AEM survey (acquired with the RESOLVE frequency domain system) to provide information in relation to salinity management i

Interaction between a river and its wetland: evidence from the Murray River for spatial variability in diatom and radioisotope records

Sinclair Flat is small wetland, located within the gorge section of the Murray River floodplain. situated near Blanchetown, South Australia, the wetland is closely linked to the River and, since regulation, has become permanently inundated. High summer evaporation rates deplete the volume of water within the wetland. However, this is compensated by perennial inflow via a permanent inlet from the River. This site provides an opportunity to explore the relative contribution of river and wetland diatom flora to the sediment record, and the fluvial and aerial contribution of radiometric isotopes to the system. The geochronological and biostratigraphic data provide an insight into the history of the water quality of Sinclair Flat. Evidence exists for the River being a source of sediments and isotopes and of diatom species typical of the main river channel. Prior to 1950, Sinclair Flat was an oligotrophic, oligosaline, clear-water wetland. The wetland shifted gradually to an environment that favoured clear-water benthic species, most likely as a consequence of changes following river regulation in the 1920s, although the capacity to date these sediments is limited. During the 1950s, the wetland became plankton dominated. Peaks in epiphytic diatoms during the 1960s suggest increased emergent macrophyte cover. The contemporary condition is of a connected, turbid, eutrophic and mesosaline lagoon. The ecological condition of Sinclair Flat has diverged considerably from its historical range of condition. This record supports evidence from upstream of widespread state switches in the Murray–Darling Basin floodplain wetlands. This record also lends considerable weight to modern studies attesting to the degraded state of the waterways of the Murray–Darling Basin and the impact of river regulation practices on the water quality of these ecosystems.

Dynamics of Murray‐Darling floodplain forests under multiple stressors: The past, present, and future of an Australian icon

We review the human actions, proximal stressors and ecological responses for floodplain forests Australia's largest river system—the Murray‐Darling Basin. A conceptual model for the floodplain forests was built from extensive published information and some unpublished results for the system, which should provide a basis for understanding, studying and managing the ecology of floodplains that face similar environmental stresses. Since European settlement, lowlands areas of the basin have been extensively cleared for agriculture and remnant forests heavily harvested for timber. The most significant human intervention is modification of river flows, and the reduction in frequency, duration and timing of flooding, which are compounded by climate change (higher temperatures and reduced rainfall) and deteriorating groundwater conditions (depth and salinity). This has created unfavorable conditions for all life‐history stages of the dominant floodplain tree (Eucalyptus camaldulensis Dehnh.). Lack of extensive flooding has led to widespread dieback across the Murray River floodplain (currently 79% by area). Management for timber resources has altered the structure of these forests from one dominated by large, widely spreading trees to mixed‐aged stands of smaller pole trees. Reductions in numbers of birds and other vertebrates followed the decline in habitat quality (hollow‐bearing trees, fallen timber). Restoration of these forests is dependent on substantial increases in the frequency and extent of flooding, improvements in groundwater conditions, re‐establishing a diversity of forest structures, removal of grazing and consideration of these interacting stressors.