Macquarie River Research Articles

Towards cost-effective estimation of soil carbon stocks at the field scale

Accurate estimates of soil carbon stocks at the field scale are required to run market-based instruments for soil carbon, but the soil measurements required to make these estimates are expensive. Therefore, efficient sample designs are required. We explored the costs associated with estimating the mean soil carbon stocks within a 68-ha field on the old alluvial soils of the Macquarie River in central-west New South Wales (Red Chromosols or Red Luvisols). The sampling required to achieve a particular degree of accuracy depends upon the variability of soil carbon within the field. We conducted a 100-site geostatistical survey to estimate the variogram of soil carbon. We then used this variogram to consider the efficiency with which simple random and stratified sample designs can achieve a standard error <2 t/ha for the mean carbon stock to 30 cm. The stratifications considered were either purely spatial or based upon auxiliary information such as landform or sensor data. The effectiveness of localised clustering or quadrats within designs was also considered. Formulae were devised to determine the costs of implementing the different designs, based upon our experience from conducting the geostatistical survey. Only weak correlations between carbon stocks and the auxiliary information were evident, and hence the stratifications were largely ineffective. Some benefits of using quadrats were evident, since analytical and field survey costs were reduced. However, the cost (AU$2500) required to achieve the target accuracy is still considerable. The sampled field has complex pedology, and we therefore expect that these costs are larger than average. Similar studies are required to calculate sampling requirements in different locations and to determine whether these requirements can be related to factors such as soil type, parent material, or land management history.

Longitudinal spatial variation in ecological conditions in an in‐channel floodplain river system during flow pulses

AbstractA field survey was conducted during flow pulses to investigate the longitudinal spatial patterns in water quality, dissolved inorganic and organic matter, phytoplankton, planktonic bacteria, zooplankton, gross primary productivity (GPP) of phytoplankton and planktonic respiration (PR) in channels of the large floodplain system (∼124 km in length) of the Macquarie Marshes, south‐eastern Australia. Four river reaches (areas) with distinct hydrogeomorphological characteristics within the distributary zone of the lower Macquarie River were chosen for analysis of abiotic and biotic variables in their in‐stream environments. The results showed marked longitudinal spatial variation in the values within and among the measured environmental variables including such functional aspects as primary productivity and PR. The variables that tended to have increasing values in a downstream direction were conductivity, total nitrogen (TN), total phosphorus (TP), dissolved reactive phosphorus (DRP), dissolved silica, dissolved organic carbon (DOC), dissolved organic nitrogen (DON), dissolved organic phosphorus (DOP), ratio of DOC/DON and counts of planktonic bacteria. Conversely, the values that tended to decrease downstream were the ratios of TN/TP, DIN/DRP, DOC/DOP, DON/DOP and GPP/PR. Variables that had a localized peak(s) were dissolved oxygen, turbidity, dissolved inorganic nitrogen, GPP, PR and counts of cyanobacteria, diatoms, green algae, cryptomonads, protozoans, rotifers, copepods and cladocerans. Overall, two distinct ecological zones were identified within the broader distributary functional process zone (FPZ): these being the upstream zone with relatively high levels of DO, turbidity, diatoms and GPP/PR ratio, and the downstream zone with relatively high levels of nutrients, dissolved organic matter, cyanobacteria, planktonic bacteria, protozoans and cladocerans. The results of this study describe the spatial connectivity of ecological processes related to hydrogeomorphological factors within a FPZ of a riverine ecosystem, and support the predictions of the riverine ecosystem synthesis framework that ecological patterns and processes can be discontinuous on a longitudinal spatial scale. Copyright © 2010 John Wiley & Sons, Ltd.

Statistically Integrated Flow and Flood Modelling Compared to Hydrologically Integrated Quantity and Quality Model for Annual Flows in the Regulated Macquarie River in Arid Australia

Water resource management traditionally depends on use of highly complex hydrological models designed originally to manage water for abstraction but increasingly relied on to determine ecological impacts and test ecological rehabilitation opportunities. These models are rarely independently tested. We compared a relatively simple statistical model, integrated flow and flood modelling (IFFM), with a complex hydrological model, the integrated quality and quantity model (IQQM), on the highly regulated Macquarie River of the Murray-Darling Basin, southeastern Australia. We compared annual flows (1891-2007) at three gauges to actual data and modelled output: before dams and diversions (unregulated) and after river regulation (regulated), using the goodness of fit (Nash-Sutcliffe coefficient of efficiency) and nonparametric tests. IQQM underestimated impacts of river regulation respectively on median and average flows at the Macquarie Marshes (Oxley gauge) by about 10% and 16%, compared to IFFM. IFFM model output more closely matched actual unregulated and regulated flows than IQQM which tended to underestimate unregulated flows and overestimate regulated flows at the Ramsar-listed wetland. Output was reasonably similar for the two models at the other two flow gauges. Relatively simple statistical models could more reliably estimate ecological impact at floodplains of large river systems, as well as an independent assessment tool compared to complex hydrological models. Finally, such statistical models may be valuable for predicting ecological responses to environmental flows, given their simplicity and relative ease to run.

Paleoecological responses to avulsion and floodplain evolution in a semiarid Australian freshwater wetland

Paleoecological responses to coupled geomorphic and hydrological changes have rarely been studied using a multiproxy approach in freshwater floodplain wetlands of semiarid Australia. The Macquarie Marshes are a large, multi-channelled and morphodynamic floodplain wetland system in the lowland interior of the Murray-Darling Basin, southeastern Australia. Evidence from historical maps, aerial photographs, geomorphology and sedimentology indicate that avulsion in the southern Macquarie Marshes caused the formation of a major new channel (Monkeygar Creek) and the abandonment of a reach of the Macquarie River in the last 200 years. Paleobiological samples from near-uniform sediment cores were studied to determine the environmental changes related to this avulsion, as well as associated floodplain evolution and hydrological changes in the adjoining flood-reliant wetlands. Fifteen macrophyte taxa, seven charophyte taxa, 28 diatom taxa and 18 aquatic invertebrate taxa were identified in sediments from the terminal reach of the Macquarie River and the active lower reach of Monkeygar Creek. Paleoecological reconstruction indicates that the slowly accreting marsh (ca 0.032 to 0.037 cm a−1) around the Macquarie River (Terminus Marsh) was more frequently and deeply inundated in the past (presence of limnetic zooplankton before ca 1626 cal. years BP) than during the penultimate pre-avulsion phase (absence of limnetic zooplankton and more diverse terrestrial and aquatic vegetation from ca 540 cal. years BP). In contrast, the floodplain near lower Monkeygar Creek was only periodically inundated prior to avulsion (high diversity of charophytes and low diversity of diatoms and invertebrates before ca 149 years BP), before experiencing disturbance, rapid accretion and ecological succession during the avulsion (paucity of wetland biota in distinct flood facies ca 149 years BP). This part of the floodplain became a substantial wetland, dominated by algae (charophytes and diatoms) and submerged macrophytes, due to a more consistent flood regime following the avulsion. The contemporary marsh on lower Monkeygar Creek has evolved in the last ca 54 years into a shallower, less frequently flooded wetland (new dominance of emergent macrophytes, charophytes and littoral cladocerans), probably due to changes in inundation caused by rapid local floodplain accretion (ca 0.409 to 0.556 cm a−1) and possibly river regulation. This multiproxy approach provides some of the first evidence of significant changes in wetland communities and ecological successions that are directly related to the geomorphic processes of avulsion and floodplain evolution in a semiarid wetland system such as the Macquarie Marshes.

Feeding-preference trials confirm unexpected stable isotope analysis results: freshwater macroinvertebrates do consume macrophytes

The loss of connectivity in intermittent streams can limit aquatic-invertebrate access to food resources, with different resources available in individual pools. Although leaf litter was abundant in the Macquarie River in Tasmania, stable carbon and nitrogen isotope analyses suggested that aquatic macrophytes were more prevalent in shredding macroinvertebrate diets. We tested this result with two multi-choice trials, which examined the feeding preferences of Atalophlebia albiterminata (Ephemeroptera) and the case-building trichopterans Lectrides varians, Notalina bifaria, Triplectides similis and T. ciuskus ciuskus. We first tested preferences for the dominant benthic leaf species (Acacia mucronata, Eucalyptus amygdalina, E. barberi, E. obliqua and E. viminalis). We hypothesised that macroinvertebrates would preferentially select leaves with lower chemical concentrations. However, there were no strong preferences for conditioned leaves by any invertebrate, although the leaves varied in toughness, tannin, nitrogen and allelochemical content. Second, we examined the preferences for E. amygdalina and E. barberi leaves or the fresh macrophytes Triglochin procerum, Myriophyllum salsugineum and Potamogeton tricarinatus. Macrophytes were preferred over leaves by all invertebrates, with T. procerum significantly preferred over the other macrophytes. This suggests that macrophytes may be undervalued in riverine food webs, and should be included in analyses of food webs using stable isotopes.

Bathurst Plains and beyond: European colonisation and Aboriginal resistance

The colonisation of the Bathurst Plains and adjacent areas on the upper Macquarie River and Lachlan River tributaries incorporated reciprocal processes; the gradual modification of the coloniser's British land use pattern into a recognisably Australian pattern, and the gradual erosion, followed by the rapid collapse, of the Aboriginal land use pattern. The European colonisation of the Bathurst Plains elicited one of the strongest Aboriginal reactions met with to that date. The analysis of that resistance gives an insight into both the nature of Aboriginal settlement in the area, and the changes taking place in the European settlement pattern, and shows that while in some ways the Bathurst experience differed substantially from later conflict on the pastoral frontier in New South Wales, it does help to explain that subsequent contact history.

Landholder views on the boundaries of the Macquarie Marshes

The Macquarie Marshes are an extensive wetland system, situated at the lower end of the Macquarie River in central western NSW. The marshes are the focus of considerable debate over management issues. The Macquarie Marshes Catchment Committee is preparing a Land and Water Management Plan to deal with these issues. The necessary first step in this planning process was exploring the concept of a boundary of marshes and defining a boundary of an appropriate planning area, including the marshes. Community views on wetland boundaries were determined from the results of semi-structured interviews and a landholder questionnaire. Following negotiations, particularly with landholders who considered that they did not own marsh country, an acceptable planning area was defined for the purpose of the planning process. With the outer planning area boundary determined, specific management options can then be considered for either the whole are or for components of this study area e.g. for specific vegetation types. Scientific data and the political context were also explored to provide a background to the decision on a planning area. The interaction of factors which led to the decision as well as difficulties in delineating a boundary are discussed.

Downstream hydrogeomorphic changes along the Macquarie River, southeastern Australia, leading to channel breakdown and floodplain wetlands

Floodplain wetlands and floodouts in the Macquarie Marshes are fed by numerous anastomosing and distributary channels on the lower reaches of the Macquarie River, southeastern Australia. River discharge is seasonally and annually variable and is affected by both interannual and interdecadal climatic trends, related to ENSO and IPO. A downstream comparison of hydrologic data shows that flows decrease significantly in magnitude and stream power along the allogenic lower Macquarie River as distributary outflows are not matched by tributary inputs. Intrinsic hydrologic and geomorphic thresholds along the lower Macquarie River lead to the breakdown of the trunk stream into smaller distributaries, with disintegration of channelised flows and development of extensive wetlands on the low-gradient, dryland alluvial floodplain-fan. Cross-sectional analysis shows that the morphology and morphometry of the trunk stream change accordingly, with adjustments in planform and cross-sectional shape and marked downstream reductions in channel capacity and bed width. Despite monotonic declines in river discharge, gross stream power and channel cross-sectional area, there is a threshold change in the geomorphic response. Channel width-to-depth ratio decreases in the middle reaches and then increases, while channel sinuosity increases until immediately upstream of the core wetlands and then rapidly declines as straight channels enter areas of extensive channel breakdown. Floodplain width is greatest on the alluvial plain, allowing a broader area of floodplain wetlands to develop, that are characterised by fine cohesive sediments. Floodplain connection is greatest where floodouts and wetlands form in the Marshes. Channel breakdown and floodplain wetland formation along the lower Macquarie River and in the Macquarie Marshes are distinct examples of a nonequilibrium response to downstream declining discharge and stream power, which is an inherent condition in many dryland Australian rivers during the Holocene.

The Opera House of the West

I turn off the Mitchell Highway outside the New South Wales town of Wellington and drive east into undulating pastoral lands. From here it is about 30 kilometres to the Burrendong Dam, an earth-filled structure across the Macquarie River that was once dubbed ‘The Opera House of the West’. It is difficult to associate this lonely rural valley with a bustling quay and a building that gleams with over a million white and cream tiles. On a treeless rise I can see a brick farmhouse but there is no movement, not even a car parked in its pale gravel driveway. There are no fellow travellers on this narrow road. After winter rain the grass is not high, but it is green, and afternoon sun catches the ridges of low north-south running hills, creating parallel lines of gold and shade across the slopes.

Gem-corundum megacrysts from east Australian basalt fields: trace elements, oxygen isotopes and origins*

Gem corundum, a minor but persistent megacryst in east Australian basalt fields, is mined from some placer concentrations. Laser ablation, inductively coupled plasma mass spectrometry analyses and O isotope determinations on a colour range of corundum from different fields, show that chromophore (Fe, Cr, Ti, V) and genetic indicator (Ga, Mg, δ18O) values can distinguish corundum sources (magmatic, metamorphic and metasomatic) before basalt incorporation. They also characterise corundum groups from different fields. This identified two metamorphic groups, one carrying ruby at Barrington Tops, and a magmatic group distinct from those from other gem fields (lower Fe, northeast Tasmania; higher Fe, Yarrowitch). Ruby-bearing groups show clear provincial characteristics and include lower temperature spinel-facies groups (Barrington, Yarrowitch) and higher temperature garnet-facies groups (Cudgegong–Macquarie River). High Mg/Fe and Ni values in the latter approach those for corundum in diamond, and are a possible diamond indicator. The corundum derived from diverse fold-belt and felsic sources in underlying lithosphere forms a dataset for comparing corundum from other basalt fields.

Modelling flow to and inundation of the Macquarie Marshes in arid Australia

AbstractBuilding of dams and subsequent abstraction upstream of rivers significantly affects major wetland systems. Knowledge of anthropogenic impacts of river regulation, relative to stochastic variation, is essential if managers are able to adequately manage flows to wetlands. We built annual flow and inundated area models for the Macquarie Marshes supplied by the Macquarie River, based on available annual rainfall data (1879–2006). We used LOESS, the flexible local polynomial regression method, ideal for modelling complex processes where no theoretical models exist. To compare effects of river regulation and abstraction, we developed two models, before river regulation (‘natural’ or ‘unregulated’) and after river regulation (‘regulated’). The division was when Burrendong dam, the most significant regulatory structure affecting flows, was built in 1963 and completed in 1967. After this point, water was diverted upstream, predominantly for irrigation. We developed ‘natural’ and ‘regulated’ flow models for three flow gauges Dubbo, Warren and Oxley based on annual rainfall at rainfall stations in the upper catchment and flow, and then inundated area models based on flow and local rainfall to fit annual inundated area data (1979–2006) in the Macquarie Marshes, using LOESS and leave‐one‐out samples without overfitting. We evaluated the performance of the proposed models and used these models to predict annual flows and inundated areas from 1879 to 2006. Comparison was done in terms of ‘natural’ and ‘regulated’ data using Kolmogorov–Smirnov test, identifying significant reductions in flow and wetland area. Copyright © 2009 John Wiley & Sons, Ltd.

Geomorphic environments, drainage breakdown, and channel and floodplain evolution on the lower Macquarie River, central-western New South Wales

The Macquarie River of eastern Australia is an inland draining perennial system whose lower reaches flow across a large, low-gradient alluvial plain without tributary input. Failure of the Macquarie to sustain its channelled meandering course results in channel breakdown and the development of a broad distributary pattern characterised by a network of discontinuous anabranching and distributary channels and associated permanent and semi-permanent wetlands. The location of the channel breakdown region results from a combination of channel hydrology and sediment load. However, at the local scale, the complete breakdown into unchannelised marshes is influenced by the degree of topographic confinement produced by surrounding paleo-alluvial ridges. Several distinctive marsh channel types are identified on the lower Macquarie, each playing a different role in the process of channel and floodplain evolution. In general, new marsh channels are initiated by avulsion and incision into the floodplain surface and then gradually aggrade until a new avulsion results in abandonment, typically over a time-scale of ∼100 a. Floodplain development occurs as a series of spatially discrete sediment lobes, each of which are deposited in permanent swamps immediately downstream of the channel breakdown. The swamps trap almost all of the sediment delivered to them. Despite this, low suspended sediment concentrations result in slow rates of floodplain accretion. Lobe accretion is terminated by channel avulsion through low levees at the channel margin. Avulsion and channel breakdown at the local scale are driven by the characteristic nature of the dense in-channel reed vegetation which chokes the streams and leads to in-channel aggradation, reduced fluvial efficiency and frequent overbank flows that ultimately lead to the development of new channels.

“ Beong! Beong! (more! more!)”: John Harper and the Wesleyan Mission to the Australian Aborigines

“Beong! Beong! (more! more!)”: John Harper and the Wesleyan Mission to the Australian Aborigines David A. Roberts and Hilary Carey I said to them in their own language “Were gairer” be not afraid, at which words they sat down and became quite composed. One of them was much pleased to hear me speak in the native tongue, and exclaimed “Beong! Beong!” (more more) Harper Journal, 5 March 1825).1 In July 1826, two Methodist gentlemen sat down for a tense meeting with the New South Wales (NSW) Attorney-General, Saxe Bannister (1790–1877): the Rev. Ralph Mansfield, Secretary, and William Horton, Treasurer, represented the NSW Auxiliary of the Wesleyan Methodist Missionary Society (WMMS).2 The matter at hand was a controversy that had arisen from a venture undertaken by the Society on a remote penal establishment on the frontier at Wellington Valley on the lower Macquarie River about 100 kilometres north-west of Bathurst in central-western NSW. In particular, there were questions to be answered about the conduct of a young missionary, John Harper (c. 1800–1862), who was alleged to have publicly misrepresented the short-term results and long-term prospects for the evangelization of the Wiradjuri people native to the area.3 It was reported in the press – but widely disbelieved – that Harper had already begun the translation of scripture (‘which implies a grammatical knowledge of the structure of the language’), that the people were so entranced by his facility in the language that they had begged him “Beong! Beong!” (more! more!), and that he had affected such a change in the morality of the native people that not only did they forbear swearing but had ceased to force their wives to have illicit intercourse with male convicts. The intervention of the Attorney-General is a fair indication of the political sensitivity of Harper’s claims and their possible repercussions for government policy relating to the small community of Wesleyan Methodists in the colony and their fledgling missionary activities. In the early decades of the nineteenth century, the political engagement and enthusiasm of Methodist missionaries in British colonies had been persistently controversial; the threat of scandal in New South Wales was, potentially, highly embarrassing to both church and state. In the Cape Colony, the involvement of Wesleyan and other missionaries in a campaign to denounce what they saw as the oppression of native people by settlers was to be a significant factor in ongoing hostility between English and Dutch colonizers. Under the cover of a humanitarian campaign against “spiritual and social bondage,” it was generally believed by Dutch settlers that missionaries, backed by the British government, were attempting to subvert their claims to land and their control and access to native labor.4 As Elizabeth Elbourne, Richard Elphick and others have argued, the intervention by missionaries in the Cape was part of a religious and cultural campaign in which settlers, missionaries and imperial administrators contested the moral purpose of empire. The Cape was not the only colonial site where Methodist missionaries were engaged. In 1825 Thomas Fowell Buxton, the parliamentary leader of the anti-slavery party that had succeeded in securing the abolition of the Atlantic slave trade in 1807 and who was later instrumental in the appointment of a Select Committee to inquire into the treatment of Aboriginal people in British colonies in southern Africa, Australia and North America, had raised questions in parliament about the demolition of the Methodist Chapel in Barbados in what appeared to be retaliation for the church’s agitation on behalf of slaves.5 In his speech on this occasion, Buxton’s words echo claims made by Harper for his work with the Australian Aborigines: “Mr Shrewsbury had devoted himself laboriously to the improvement of the negroes, and with the best results. Instruction was gaining ground; marriages became more frequent; the marriage tie was held more sacred.”6 Shrewsbury was obliged to suffer constant harassment which Buxton called “the common lot of a Methodist Missionary”: planters would walk into the Wesleyan chapel on a Sunday, failing to remove their hats and whistling, provocative acts which escalated into a full-scale riot on October 5, 1823 during which a mob consisting of...

Stone Arrangements and other Relics of the Aborigines Found on the Lower Macquarie River, N.S.W., at and near Mount Foster and Mount Harris.

Stone Arrangements and other Relics of the Aborigines Found on the Lower Macquarie River, N.S.W., at and near Mount Foster and Mount Harris.

Observations on the ecology of the Barking OwlNinox connivenswithin the lower Macquarie River floodplain of New South Wales

Sixteen Barking Owl Ninox connivens records, accounting for 29 birds were made by Department of Infrastructure, Planning and Natural Resources (DIPNR) staff from 1996-2004 within the lower Macquarie River floodplain in New South Wales. Records suggest a strong association between owl presence and riparian River Red Gum E. camaldulensis forest / woodland. Nearest neighbour distances between records were similar to those found elsewhere on the NSW central west slopes and plains.

A Bayesian decision network approach for assessing the ecological impacts of salinity management

This paper outlines one component of a study being undertaken to provide a new tool for integrated management of dryland salinity, a major environmental problem in Australia. The Little River Catchment in the upper Macquarie River basin of New South Wales (NSW) is used as a case study. A Bayesian decision network (BDN) approach integrates the various system components — biophysical, social, ecological, and economic. The method of integration of the system components is demonstrated through an example application showing the impacts of various management scenarios on terrestrial and riparian ecology. The ecological impacts of management scenarios are assessed using a probabilistic approach to evaluate ecological criteria which are compared with those for the present situation. In considering different ecological indices, the direction and magnitude of change under different management scenarios varies because of the diverse influence of habitat fragmentation.

Waterbird breeding and environmental flow management in the Macquarie Marshes, arid Australia

AbstractColonial waterbirds breed in relatively few parts of Australia and the Macquarie Marshes are one of the more important wetlands for these species on the continent in terms of size of breeding colonies and frequency of breeding. Breeding data were collected for ten species of colonial waterbirds in the period 1986–2001: Little Black Cormorant Phalacrocorax sulcirostris, Little Pied Cormorant P. melanoleucos, Great Egret Ardea alba, Intermediate Egret A. intermedia, Little Egret A. garzetta, Cattle Egret A. ibis, Rufous Night Heron Nyctiorax caledonicus, Glossy Ibis Plegadis falcinellus, Straw‐necked Ibis Threskiornis spinicollis and Australian White Ibis T. molucca. Breeding of most colonial waterbirds in the Macquarie Marshes was positively related to flow in the three months before breeding and triggered when flows were usually above 200 000 Ml. Flow was also positively related to wetland area. These relationships allowed modelling of three different options for management of environmental flow, nominally an annual allocation of 125 000 Ml. Even though the Macquarie River is highly regulated, there were predicted to be major differences in breeding frequency, flow variability and wetland flooding for different options delivering environmental flows. Use of all environmental flows each year provided the least variable option while accumulating the flow in the major dam and delivering it at high thresholds provided considerably more variability for the Macquarie Marshes, increased breeding of colonial waterbirds and increased frequency of large floods. The size of a waterbird breeding event and flooding extent were still primarily affected by river flooding and diversions upstream, despite the amount of environmental flow and the predicted ecological differences among the environmental flow options. Copyright © 2005 John Wiley & Sons, Ltd.

Evidence of Late Cenozoic uplift and climate change in the stratigraphy of the Macquarie River valley, New South Wales

The stratigraphy of the alluvial sediments filling the Macquarie River valley, New South Wales, was investigated to test models of landscape evolution of the rifted margin Eastern Highlands of Australia. In the neighbouring Lachlan River valley, the stratigraphy of Neogene sediments has been incorporated into a model proposing denudation and episodic passive (denudational isostatic) uplift of the highlands throughout the Neogene. In this study, we aimed to test the regional extent of this model and the influence of sediment supply on the stratigraphic record and its interpretation. The sediments of the Macquarie River valley show three major changes in the depositional regime. First, erosion of the valley basement in the Late Miocene was followed by (and possibly synchronous with) deposition of a basal clay and sand unit in the Late Miocene. Second, the valley was filled with a wedge of sediment containing abundant gravel and sand in the Pliocene; and third, the older gravelly unit was eroded and reworked in the Quaternary, and a sandy clay unit, which forms the modern floodplain, was deposited. Deformation of the Middle Miocene basalt‐filled valley provides good evidence for substantial uplift of the highlands in the Middle‐Late Miocene, synchronous with or shortly after wide‐spread volcanism, but continuing no later than the Late Miocene. The Pleistocene incision is best accounted for by climate change to drier conditions, triggering a sediment‐starved response by the Macquarie River, rather than further uplift. While valley incision and subsequent infilling can be viewed as a response to tectonism, the internal sedimentology and stratigraphy of the sediments appears to respond to fluctuations in sediment supply brought about by extrinsic climate change and intrinsic catchment lithology. The first‐order tectonic events are not synchronous with uplift in the Lachlan valley and are restricted to relatively local spatial scales. However, the secondary climatic forcing has a broader regional expression.

Modelling the impacts of strategic tree plantings on salt loads and flows in the Macquarie River Catchment, NSW, Australia

In Australia, problems of dryland and stream salinity have recently become the focus of a National Action Plan. In many river catchments, preliminary stream salt load and salinity targets have been set to define maximum permissible export levels in 2015. Afforestation has been proposed as a strategy for meeting these targets, although several studies suggest that widespread commercial tree plantations are likely to deliver net dis-benefits. However, the impacts on stream salt loads of more localised tree plantings in high salt yielding areas have not been quantified. In this paper we use a simple empirical model to predict the effects of various strategic and non-strategic tree planting scenarios on flows and salt loads in the mid-Macquarie catchment, New South Wales. A simple salt routing model is then used to estimate the effect of these changes on salt loads at the end-of-valley monitoring site for the Macquarie catchment. Results suggest that widespread land management interventions will be required to meet the preliminary salt load targets for this catchment. On their own, small-scale, strategic tree planting in high salt export areas of the mid-Macquarie area will not have a significant impact on salt loads at the end-of-valley monitoring site. While widespread tree plantings may reduce salt loads in the longer term, they are likely to cause streamflow losses in the shorter term. Thus, stream salinities are expected to rise initially, due to the different response times of groundwater and surface water systems to land use change.

The effects of large-scale afforestation and climate change on water allocation in the Macquarie River catchment, NSW, Australia

Widespread afforestation has been proposed as one means of addressing the increasing dryland and stream salinity problem in Australia. However, modelling results presented here suggest that large-scale tree planting will substantially reduce river flows and impose costs on downstream water users if planted in areas of high runoff yield. Streamflow reductions in the Macquarie River, NSW, Australia are estimated for a number of tree planting scenarios and global warming forecasts. The modelling framework includes the Sacramento rainfall-runoff model and IQQM, a streamflow routing tool, as well as various global climate model outputs from which daily rainfall and potential evaporation data files have been generated in OzClim, a climate scenario generator. For a 10% increase in tree cover in the headwaters of the Macquarie, we estimate a 17% reduction in inflows to Burrendong Dam. The drying trend for a mid-range scenario of regional rainfall and potential evaporation caused by a global warming of 0·5°C may cause an additional 5% reduction in 2030. These flow reductions will decrease the frequency of bird-breeding events in Macquarie Marshes (a RAMSAR protected wetland) and reduce the security of supply to irrigation areas downstream. Inter-decadal climate variability is predicted to have a very significant influence on catchment hydrologic behaviour. A further 20% reduction in flows from the long-term historical mean is possible, should we move into an extended period of below average rainfall years, such as occurred in eastern Australia between 1890 and 1948. Because current consumptive water use is largely adapted to the wetter conditions of post 1949, a return to prolonged dry periods would cause significant environmental stress given the agricultural and domestic water developments that have been instituted.