Burdekin River Catchment Research Articles

Enhancing whole-of-river conservation

We argue for improved conservation of freshwater ecosystems at catchment or eco-regional scales by explicit assignment of values to all river sections and wetlands, recognising current disturbance, and aiming for ‘no further harm’ to the commons. The need is indicated by the global deterioration of biodiversity and ecosystem services of rivers and wetlands, increasing demands on water and land resources, and climate change. Regional pressures include multiple jurisdictions, competing demands, piecemeal management, pollution and habitat impacts. Effective resource and conservation management needs to integrate multiple uses via governance of activities of stakeholders, recognising hydrogeomorphic, water quality and ecological properties of ecosystems. Complete ecological protection is impractical amidst water-resource and land-use development, but we suggest that all river reaches and wetlands be given a conservation rating based on habitat, biodiversity and connectivity values. We present a straightforward approach to spatial conservation rating of freshwaters, using hydrogeomorphic typology and assignment of conservation values on the basis of available information and expert elicitation. We illustrate the approach by using the large Burdekin River catchment in north-eastern Australia. This approach is complementary to more spatially focused conservation prioritisation and could greatly improve management for sustainability, reduce further decline in conservation values, and facilitate rehabilitation.

First report of strong phosphine resistance in stored grain insects in a far northern tropical region of Australia, combining conventional and genetic diagnostics

Although phosphine resistance monitoring and management programs are well advanced in Australia, the tropical northern part of the continent has received little attention. To address this, grain storages were sampled in the Townsville region in the Burdekin river catchment area of northern Queensland, and insect populations were subjected to resistance testing. Sampling of storages including silos, food processing facilities and feedlots was carried out during July to August 2019 and February to March 2020. Of the several species collected, populations of two major pest species, Rhyzopertha dominica and Tribolium castaneum were subjected to phenotypic resistance and molecular screening using discriminating doses and gene specific DNA marker, respectively. Utilising phenotypic assay, of the 17 populations of R. dominica, 12 were diagnosed as weakly resistant and five as strongly resistant; whereas of the 34 populations of T. castaneum, two were found to be susceptible to phosphine, 15 were determined as weakly resistant and 17 as strongly resistant. The molecular diagnostics, however, determined rph2 alleles for strong resistance in some populations each of R. dominica and T. castaneum that were diagnosed as weakly resistant in the phenotypic assay. The most prevalent rph2 alleles were found to be P49S and K142E in R. dominica populations and P45S and G131S in T. castaneum populations. Our results highlight the need of more comprehensive study towards determining the level of pests and resistance risks in this region.

Preventable fine sediment export from the Burdekin River catchment reduces coastal seagrass abundance and increases dugong mortality within the Townsville region of the Great Barrier Reef, Australia

The coastal seagrass meadows in the Townsville region of the Great Barrier Reef are crucial seagrass foraging habitat for endangered dugong populations. Deteriorating coastal water quality and in situ light levels reduce the extent of these meadows, particularly in years with significant terrestrial runoff from the nearby Burdekin River catchment. However, uncertainty surrounds the impact of variable seagrass abundance on dugong carrying capacity. Here, I demonstrate that a power-law relationship with exponent value of −1 (R2~0.87) links mortality data with predicted changes in annual above ground seagrass biomass. This relationship indicates that the dugong carrying capacity of the region is tightly coupled to the biomass of seagrass available for metabolism. Thus, mortality rates increase precipitously following large flood events with a response lag of <12-months. The management implications of this result are discussed in terms of climate scenarios that indicate an increased future likelihood of extreme flood events.

Paired geochemical tracing and load monitoring analysis for identifying sediment sources in a large catchment draining into the Great Barrier Reef Lagoon

While sediment tracing has been typically applied to identify sediment sources that are difficult to measure by gauging (monitoring), it can also be useful in estimating relative sediment yields from gauged river catchments. The major and trace element composition of river sediments from eleven locations in the 130000km2 Burdekin River catchment, northeastern Australia was analysed to examine relative contributions from upstream source areas in the 2011/12 water year. Sediment tracing results are compared against estimates derived from sediment load monitoring at three locations. Comparisons show that there is good agreement between tracing results and monitoring data at one of the tributary confluences. At the second site, notable contrasts were found between the load estimates from the monitoring and tracing data. At this site a large impoundment occurs between the upstream sampling/gauging sites for source sediments and the downstream sampling/gauging sites for target sediments. The contrast is likely caused by temporal variations in particle size distributions of suspended sediment from each river and differential trapping efficiencies in the impoundment for sediment derived from the different tributaries. In the absence of the detailed particle size data and trapping efficiency estimates, sediment tracing provides the unique opportunity to elucidate source contributions of the finer fractions of suspended sediment. At a third site, where there were recognised measurement gaps in the monitoring data during large discharge events, the relative load estimates from the tracing data provided a means of constraining the recognized uncertainty of monitored load estimates. We conclude that sediment tracing can be used as a valuable adjunct to monitoring data particularly in remote, large and data-sparse catchments. Both tracing results and monitoring data show that the Upper Burdekin River and Bowen-Bogie Rivers were the dominant source of the <10μm sediments being delivered to the GBR lagoon from the Burdekin River catchment in the 2011/12 water year. More substantial contribution from the Belyando-Suttor Rivers indicated by the tracing results than the monitoring data is attributed to preferential delivery of the 1–10μm sediments through the impoundment and has uncovered a knowledge gap in sediment budgets in the catchment.

Assessing the impact of price changes and extreme climatic events on sediment loads in a large river catchment near the Great Barrier Reef

Ocean turbidity (associated with sediment from rivers) can significantly impact reef health. In Australia, there are many plans to reduce sediment loads by encouraging best management practices; there is also interest in the use of market‐based instruments. But it is exceedingly difficult to assess the potential efficacy of market policies, since that requires one to determine how changes in the socio‐economic system (e.g. price changes) impact the biophysical (e.g. sediment loads). We use historical data (from 1938 to 2011) in a vector autoregression model to simultaneously model interactions between the economic and biophysical systems in the Burdekin River catchment adjacent to the Great Barrier Reef (GBR) lagoon. This allows us to statistically test for the impact of changes in prices on sediment load, while controlling for biophysical influences. We find that extreme events have the most impact on sediment loads, but that prices also impact sediment loads. Evidently market‐based policies may have the potential to reduce sediment loads. Our empirical results provide useful information for those interested in the Burdekin River catchment and the GBR; the modelling approach may have wide applicability in a variety of contexts.

Clay mineral source tracing and characterisation of Burdekin River (NE Australia) and flood plume fine sediment

Purpose The purpose of this study is to define the relative contributions of fine (<10 μm) suspended sediment from tributaries within the Burdekin River catchment, NE Australia, and subsequent delivery to the Great Barrier Reef (GBR) lagoon. The temporal variability in these contributions was also investigated.

Fine‐suspended sediment and water budgets for a large, seasonally dry tropical catchment: Burdekin River catchment, Queensland, Australia

AbstractThe Burdekin River catchment (∼130,400 km2) is a seasonally dry tropical catchment located in north‐east Queensland, Australia. It is the single largest source of suspended sediment to the Great Barrier Reef (GBR). Fine sediments are a threat to ecosystems on the GBR where they contribute to elevated turbidity (reduced light), sedimentation stress, and potential impacts from the associated nutrients. Suspended sediment data collected over a 5 year period were used to construct a catchment‐wide sediment source and transport budget. The Bowen River tributary was identified as the major source of end‐of‐river suspended sediment export, yielding an average of 530 t km−2 yr−1 during the study period. Sediment trapping within a large reservoir (1.86 million ML) and the preferential transport of clays and fine silts downstream of the structure were also examined. The data reveal that the highest clay and fine silt loads—which are of most interest to environmental managers of the GBR—are not always sourced from areas that yield the largest total suspended sediment load (i.e., all size fractions). Our results demonstrate the importance of incorporating particle size into catchment sediment budget studies undertaken to inform management decisions to reduce downstream turbidity and sedimentation. Our data on sediment source, reservoir influence, and subcatchment and catchment yields will improve understandings of sediment dynamics in other tropical catchments, particularly those located in seasonally wet‐dry tropical savannah/semiarid climates. The influence of climatic variability (e.g., drought/wetter periods) on annual sediment loads within large seasonally dry tropical catchments is also demonstrated by our data.

Rehabilitating degraded frontage soils in tropical north Queensland

The extensive tropical grasslands of north Queensland are grazed by beef cattle and provide a significant proportion of the water flowing into the Great Barrier Reef (GBR) lagoon. Soil sediments and nutrients eroding from the grazing lands of the Burdekin and Fitzroy catchments in north-east Queensland contribute to reduced water quality in the GBR lagoon. Degraded and eroded D-condition bare areas and eroding gullies in grazing lands provide a disproportionate amount of soil and nutrient losses from predominantly native pasture grasslands used for cattle grazing. Rehabilitating these degraded areas will help improve water quality flowing onto the reef. Rehabilitation methods were evaluated on 3 soil types on a degraded creek frontage in the Burdekin River catchment of north Queensland over the 2011/12 summer. These bare patches occur widely across the 2 catchments and consistently degraded sites have been identified by 24 years of satellite imagery. The objectives of this study were to identify mechanical methods and management practices for regenerating pasture on these bare patches. This will assist landholders in returning unproductive land to useful grazing pastures and will provide benefits to the wider community by improving quality of water from grazing lands that enters the GBR lagoon.

Quantifying total suspended sediment export from the Burdekin River catchment using the loads regression estimator tool

The loads regression estimator (LRE) was introduced by Wang et al. (2011) as an improved approach for quantifying the export of loads and the corresponding uncertainty from river systems, where data are limited. We extend this methodology and show how LRE can be used to analyze a 24 year record of total suspended sediment concentrations for the Burdekin River. For large catchments with highly variable discharge such as that of the Burdekin River, it is important to quantify loads and their uncertainties accurately to determine the current load and to monitor the effect of changes in catchment management. The extended methodology incorporates (1) multiple discounted flow terms to represent the effect of flow history on concentration, (2) a term that captures sediment trapping and spatial sources of flow in terms of the ratio of flow from above the Burdekin Falls Dam, and (3) catchment vegetation cover. Furthermore, we validated model structure and performance in relation to the application tested. We also considered errors in gauged flow rates of 10% that were consistent with the literature. The results for the Burdekin site indicate substantial variability in loads across years. The inclusion of vegetation cover as a predictor had a significant impact on total suspended sediment (TSS) concentration, with values up to 2.1% lower noted per increasing percentage of vegetation cover. TSS concentration was up to 38% lower in years with greater proportions of flow from above the dam. The extended LRE methodology resulted in improved model performance. The results suggest that management of vegetation cover in dry years can reduce TSS loads from the Burdekin catchment, and this is the focus of future work.

A Bayesian Approach to Predictor Selection for Seasonal Streamflow Forecasting

AbstractStatistical methods commonly used for forecasting climate and streamflows require the selection of appropriate predictors. Poorly designed predictor selection procedures can result in poor forecasts for independent events. This paper introduces a predictor selection method for the Bayesian joint probability modeling approach to seasonal streamflow forecasting at multiple sites. The method compares forecasting models using a pseudo-Bayes factor (PsBF). A stepwise expansion of a base model is carried out by including the candidate predictor with the highest PsBF that exceeds a selection threshold. Predictors representing the initial catchment conditions are selected on their ability to forecast streamflows and predictors representing future climate influences are selected on their ability to forecast rainfall. The final forecasting model combines selected predictors representing both initial catchment conditions and future climate influences to jointly forecast seasonal streamflows and rainfall. Applications of the predictor selection method to two catchments in eastern Australia show that the best predictors representing initial catchment conditions and future climate influences vary with location and forecast date. Antecedent streamflows are the best indicator of the initial catchment conditions. Predictors representing future climate influences are only selected for forecasts made between July and January. Indicators of El Niño dominate the selected predictors representing future climate influences. The skill of streamflow forecasts varies considerably between locations and throughout the year. Skill scores for the perennial streams of the Goulburn River catchment exceed 40% for several seasons, while for the intermittent streams in the Burdekin River catchment, the skill scores are lower.

Multisite probabilistic forecasting of seasonal flows for streams with zero value occurrences

Skillful and reliable forecasts of seasonal streamflows are highly valuable to water management. In a previous study, we developed a Bayesian joint probability (BJP) modeling approach for seasonal forecasting of streamflows at multiple sites. The approach has been adopted by the Australian Bureau of Meteorology for seasonal streamflow forecasting in Australia. This study extends the applicability of the BJP modeling approach to streams with zero flow occurrences. The aim is to produce forecasts for these streams in the form of probabilities of zero seasonal flows and probability distributions of above zero seasonal flows. We turn a difficult mathematical problem of mixed discrete‐continuous multivariate probability distribution modeling into one of continuous multivariate probability distribution modeling by treating zero flow occurrences as censored data. This paper presents the mathematical formulation and implementation of the modeling approach, methods for forecast verification, and results of a test application to the Burdekin river catchment in northern Queensland, Australia.

Motivations, risk perceptions and adoption of conservation practices by farmers

Society’s expectations of farmers in relation to their environmental performance are ever increasing, in general terms and in response to regional challenges. One tool for achieving environmental improvements in agriculture is the design and promotion of region-specific ‘best management practices’ (BMPs). BMPs are conservation practices aimed at reducing diffuse source pollution from agricultural lands and thus improving end-of-catchment water quality. A suite of grazing BMPs was developed for the Burdekin River catchment in Australia, which drains into the Great Barrier Reef lagoon. BMPs were developed in a consultative fashion but without explicit consideration of key factors that influence adoption, in particular farmers’ goals and risk perceptions. This paper utilises the data from a survey of 94 graziers in the Burdekin River catchment to explore whether and to what extent motivations and risk perceptions influence the adoption of BMPs. The results demonstrate clear correlations between both motivations, and risk attitudes, and the adoption of BMPs. In particular, strong conservation and lifestyle motivation translates into intrinsic motivation for adoption of conservation practices, while option values prevent strongly economically/financially motivated farmers from adopting in the absence of external incentives. We conclude that a sound understanding of farmers’ motivations and risk attitudes is required—in a regional, industry and environmental context—to tailor public investments aimed at providing relevant improvements in the environmental performance of agriculture.

The prevalence, organ distribution and fertility of cystic echinoccosis in feral pigs in tropical North Queensland, Australia

An investigation was carried out to study the prevalence of Echinococcus granulosus hydatidosis in feral pigs (Sus domesticus) in the Charters Towers region of tropical North Queensland. Data were collected from a total of 238 carcasses, which were hunted and shot in the Burdekin River catchment area. Organs of the abdominal, thoracic, and pelvic cavities were examined for the presence of hydatid cysts. In the laboratory, cysts and hydatid cyst fluids were examined under a stereoscopic binocular microscope and a compound microscope. An overall prevalence of E. granulosus hydatid cysts in feral pigs was found to be 31.1%. There was no significant difference in either sex or age between infected and non-infected feral pigs. The predilection sites of cysts were livers (23%) and lungs (62%), with more cysts in lungs (252) than livers (48). The ratio of livers to lungs infected with fertile cysts was 1:4 compared to 1:8 sterile cysts. The overall fertility of cysts was 70.1%. The percentage of fertile cysts in liver and lung was 79.2% and 68.7%, respectively. The diameter of fertile cysts ranged from 15 to over 60 mm. There was no significant difference in size between fertile and non-fertile cysts in lungs. The high prevalence rate and fertility of cysts in feral pigs confirm that feral pigs can take part in the sylvatic cycle of the parasite in the region. The public health significance of this observation is potentially very important.

Development of a stable isotope index to assess decadal‐scale vegetation change and application to woodlands of the Burdekin catchment, Australia

AbstractForty‐four study sites were established in remnant woodland in the Burdekin River catchment in tropical north‐east Queensland, Australia, to assess recent (decadal) vegetation change. The aim of this study was further to evaluate whether wide‐scale vegetation ‘thickening’ (proliferation of woody plants in formerly more open woodlands) had occurred during the last century, coinciding with significant changes in land management. Soil samples from several depth intervals were size separated into different soil organic carbon (SOC) fractions, which differed from one another by chemical composition and turnover times. Tropical (C4) grasses dominate in the Burdekin catchment, and thus δ13C analyses of SOC fractions with different turnover times can be used to assess whether the relative proportion of trees (C3) and grasses (C4) had changed over time. However, a method was required to permit standardized assessment of the δ13C data for the individual sites within the 13 Mha catchment, which varied in soil and vegetation characteristics. Thus, an index was developed using data from three detailed study sites and global literature to standardize individual isotopic data from different soil depths and SOC fractions to reflect only the changed proportion of trees (C3) to grasses (C4) over decadal timescales. When applied to the 44 individual sites distributed throughout the Burdekin catchment, 64% of the sites were shown to have experienced decadal vegetation thickening, while 29% had remained stable and the remaining 7% had thinned. Thus, the development of this index enabled regional scale assessment and comparison of decadal vegetation patterns without having to rely on prior knowledge of vegetation changes or aerial photography.

A multi-trace element coral record of land-use changes in the Burdekin River catchment, NE Australia

Previous studies have provided evidence for greater sediment input into the inner Great Barrier Reef (GBR) since the mid-nineteenth century, presumably caused by an increase in erosion due to intensive animal grazing after European settlement. Here we report a new trace element (Ba, Y, Mn) study of a Porites coral from Magnetic Island, northeastern Australia that grew continuously for 175 yr from 1813–1986. Increasing Ba and Y concentrations in the 1850–1890 coral growth bands are attributed to increased soil erosion caused by the introduction of livestock, mainly cattle, into the adjacent Burdekin River catchment, the largest contributor of suspended sediment to the GBR lagoon. In our study Y levels continued to rise with agricultural intensification; however, Ba concentrations reach a plateau after 1890, indicating that Ba/Ca ratios in near-shore corals may reflect additional factors than sediment input. Mn concentrations in the coral follow a more complicated pattern, which is clearly related to changes in catchment land-use and related erosion. Before the initiation of European settlement and the introduction of sheep into the Burdekin River catchment in 1854, coral Mn concentrations were uniformly low (< 1 ppm), yielding typical values for coral aragonite. However, after 1854, coral Mn levels rose dramatically, fluctuating in parallel with livestock numbers but with ever smaller amplitudes before reaching more normal values again by 1900. The coincidence in timing between the initial rise in coral Mn and the introduction of grazing animals in the Suttor and Belyando sub-catchments pinpoints the trace element source as the Burdekin River. A decrease in Mn levels since 1865 against a background of generally increasing land clearing, livestock numbers and sediment flux points to the existence of a transient, surficial Mn reservoir in the southern Burdekin River catchment, which is tentatively identified here as the pre-European topsoil on the Peak Range basaltic province. A brief return to moderate Mn levels between 1945–1960 is attributed to the expansion of the cattle industry into the upper Burdekin, Bowen and Suttor sub-catchments after World War II. This geochemical record confirms that trace elements in massive corals can be used to trace sediment input from neighbouring river catchments. In our study, Y concentrations are closely correlated with predicted increases in sediment flux due to land-use changes and prolonged droughts and so may be more useful than Ba for this purpose. Our Mn results attest to the rapidity of the ecosystem imbalance caused by the introduction of grazing animals, in particular, sheep into NE Australia. Within 30 yr, sheep had efficiently reworked and entirely removed the Mn-rich topsoil, which had conceivably accumulated during thousands of years of regular burning by Australia's indigenous population.

A sediment budget for a grazed semi-arid catchment in the Burdekin basin, Australia

In catchments adjacent to the Great Barrier Reef World Heritage Area in Queensland, Australia, there is a growing concern that sediments and nutrients being exported from the land are having a detrimental effect on coral reef communities. There is a need to determine the processes and rates of erosion from the major land use types, so that management intervention can be initiated to reduce sediment yields where required. This paper presents a sediment budget for Weany Creek, a 13.5 km 2 grazed semi-arid sub-catchment of the Burdekin River catchment, Australia. A range of field methods was used to measure erosion from hillslopes, gullies and stream banks, as well as identify the amount of sediment being deposited and remobilised on the bed of gullies and the stream network. The data suggests that at least during drought conditions, the primary erosion source in this catchment is gully erosion. However, the largest source of sediment in the budget is actually associated with the remobilisation of in-channel sediment stores. Overall, the sediment budget is comprised of ∼ 81% coarse material and 19% fine sediment and an agreement between the fine sediment yield estimated in the sediment budget and the yield measured at the catchment outlet is within 10%. The total sediment yield estimated for this catchment is ∼ 4205 t yr − 1 and is much lower than expected for a catchment of this size. This may reflect the drought conditions during the measurement period; however, there is also the possibility that the primary erosion sources have been exhausted, and the rates of sediment loss may be much lower now than they may have been in the past. Nonetheless, the results show that stored sediment, which may have been deposited in the channel many decades ago, is an important contributor to end of catchment sediment yields and warrants further investigation.

Nutrient loss and water quality under extensive grazing in the upper Burdekin river catchment, North Queensland

Increased sediment and nutrient losses resulting from unsustainable grazing management in the Burdekin River catchment are major threats to water quality in the Great Barrier Reef Lagoon. To test the effects of grazing management on soil and nutrient loss, five 1 ha mini-catchments were established in 1999 under different grazing strategies on a sedimentary landscape near Charters Towers. Reference samples were also collected from watercourses in the Burdekin catchment during major flow events. Soil and nutrient loss were relatively low across all grazing strategies due to a combination of good cover, low slope and low rainfall intensities. Total soil loss varied from 3 to 20 kg ha −1 per event while losses of N and P ranged from 10 to 1900 g ha −1 and from 1 to 71 g ha −1 per event respectively. Water quality of runoff was considered moderate across all strategies with relatively low levels of total suspended sediment (range: 8–1409 mg l −1), total N (range: 101–4000 μg l −1) and total P (range: 14–609 μg l −1). However, treatment differences are likely to emerge with time as the impacts of the different grazing strategies on land condition become more apparent. Samples collected opportunistically from rivers and creeks during flow events displayed significantly higher levels of total suspended sediment (range: 10–6010 mg l −1), total N (range: 650–6350 μg l −1) and total P (range: 50–1500 μg l −1) than those collected at the grazing trial. These differences can largely be attributed to variation in slope, geology and cover between the grazing trial and different catchments. In particular, watercourses draining hillier, grano-diorite landscapes with low cover had markedly higher sediment and nutrient loads compared to those draining flatter, sedimentary landscapes. These preliminary data suggest that on relatively flat, sedimentary landscapes, extensive cattle grazing is compatible with achieving water quality targets, provided high levels of ground cover are maintained. In contrast, sediment and nutrient loss under grazing on more erodable land types is cause for serious concern. Long-term empirical research and monitoring will be essential to quantify the impacts of changed land management on water quality in the spatially and temporally variable Burdekin River catchment.

Distribution and population structure of the vulnerable riparian palm Livistona lanuginose A. N. Rodd (Arecaceae) in the Burdekin River catchment, north Queensland

This study investigated the distribution and population structure of Livistona lanuginosa, a vulnerable palm that is mainly restricted to riparian areas in the Burdekin River catchment. The known population, though dispersed, is composed of small and isolated sub-populations which are located entirely on pastoral leases. Mapping of the occurrence of L. lanuginosa indicates that distribution is primarily linear in the riparian zone along first and second order streams, as well as associated flood zones. A total of 510 adult plants, recorded at the eight sites surveyed, suggests that the overall population size is limited. The population structures at four sites indicate a stable population at those sites, whilst the population structures at the other four sites indicate unstable and senescent populations. The greatest proportion of individuals is in the seedling stage, thus indicating that sufficient viable seed is being produced and that conditions for germination and the development of seedlings are favourable. However, prominent gaps in life stage classes at some sites suggest that recruitment is limited or is not taking place at those sites, and this situation is reflected in high numbers of intermediate life stage classes and adult palms compared to seedlings and lower life stage classes. Livistona lanuginosa remains largely unprotected from livestock and fire, and other exogenous disturbances throughout its limited range, and the small total population size makes it vulnerable to rapid decline given unfavourable natural conditions.

Flood behaviour of the Burdekin River, tropical north Queensland, Australia

Abstract Strongly seasonal rainfall in north Queensland, Australia, causes extremely variable fluvial discharge, and tropical cyclones commonly produce high-magnitude, short-duration floods. In the Burdekin River catchment (129 500 km 2 of eastern Queensland), rapid runoff and channel floodplain configuration lead to very fast flood-wave speeds (up to 4.34 m s −1 calculated). The large catchment and varying tropical cyclone paths result in extreme variations in flood history at different sites. Changes in channel conditions (bed elevation, vegetation, bedforms, sediment surface character) in successive events, combined with complex rainfall patterns and highly unsteady flow, make flood estimates extremely difficult. Because of the short duration of flow events and very rapid rate of change in discharge during individual events, sediment transport rate, bedforms, and bed elevation change continuously. For most of the year the channel is occupied by an underfit stream, but this small perennial stream does not significantly rework the deposits or change channel form before the next major discharge event. Consequently, there is little channel form recovery between major discharge events. Successive events have very variable size and consequently the bedforms and channel morphology are normally out of equilibrium with the flow, and record the result of the most recent major events. High-magnitude floods transport coarse sediment onto the floodplain and the short duration of flooding and rapid runoff results in relatively low preservation of mud in the channel or overbank environment. The Holocene flood deposits include thick, coarse sand and medium sand units and generally thin, fine-grained units.

Hydrology of Lake Eyre, Australia: El Niño link

All major ephemeral rivers of Australia lie in the Lake Eyre basin. Dry for years, on occasions they carry enormous floods, with annual volumes of 40 km 3 and instantaneous discharges of the order of 30,000 m 3 s −1. Mean annual runoff of the basin is 4 km 3 or 3.5 mm, significantly less than the 57 mm for the whole of Australia. This paper examines Lake Eyre and its drainage basin, describing the historical hydrology of the catchment, both in terms of instrument records and inflows hindcast using a model based on the technique of coral fluorescence palaeohydrological reconstruction. Coral fluorescence is a function of nearby-river discharge, and can be used to reconstruct annual river outputs reconstruction. Coral fluorescence is a function of nearby-river discharge, and can be used to reconstruct annual river outputs beyond the instrument period. The Burdekin River catchment runoff history is strongly paralleled by the volumes of Lake Eyre inflows during the period of common reliable instrument gaugings. The Burdekin runoff data have been extended back to 1735 A.D. using the correlation between river discharge and annual growth-band fluorescence in an old coral from Pandora Reef, off the North Queensland coast. For the instrument period 1952 to 1980, 73% of the variance between coral fluorescence and Burdekin discharge is common. During the period 1949–1980, 41% of the variance between coral fluorescence and Lake Eyre inflow data is common. Modelled inflows to Lake Eyre for the period 1885–1948 are based on the latter data set.