A Paddock to reef monitoring and modelling framework for the Great Barrier Reef: Paddock and catchment component

Carroll, Chris; Waters, David; Vardy, Suzanne; Silburn, D. M.; Attard, Steve; Thorburn, Peter J.; Davis, Aaron M.; Halpin, Neil V.; Schmidt, Michaël; Wilson, Bruce; Clark, Andrew R.

doi:10.1016/j.marpolbul.2011.11.022

Cited by 100 publications

(70 citation statements)

References 60 publications

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“…The results of this study should assist interpretation of results from the D-SedNet catchment sediment budget model , which is being applied to evaluate the effect of changing agricultural practices on river fine sediment loads to the GBR lagoon (Carroll et al 2012). In particular, the large contributions of subsurface soil erosion processes indicate that priority should be given to improved mapping of gully and riverbank erosion rates, to field experiments on the influence of grazing management practices on erosion rates (Thorburn et al 2013), and to understanding the sources, fate and ecosystem significance of particulate nutrients, which contribute the majority of nutrients to the GBR lagoon (Kroon et al 2013).…”

Section: Discussionmentioning

confidence: 99%

Sediment source tracing with stratified sampling and weightings based on spatial gradients in soil erosion

et al. 2015

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Purpose The results of sediment source tracing in large river catchments depend on defined sources being adequately represented by the sampling and in subsequent numerical analysis. We hypothesise that surface soil concentrations of fallout radionuclides caesium-137 ( 137 Cs) and lead-210 excess ( 210 Pb ex ) are smaller at locations with higher soil erosion rate and that if this is not accounted for, then spatially random sampling gives a biased representation of surface soil delivered to rivers and biased source contribution estimates. Materials and methods Surface soil was sampled across the Burdekin River basin in northeast Australia at 90 locations stratified by three classes of modelled soil erosion rate and analysed by gamma spectroscopy. Separate probability distributions (density functions) were fitted to the 137 Cs concentrations of samples of each erosion class, of subsurface soil and of river sediment. Surface soil distributions were aggregated by weighting in proportion to the upstream area and mean erosion rate of each erosion class, so that the high erosion class contributed disproportionately to the tracer properties of the surface soil source. Source contributions were estimated using a Monte Carlo mixing model. Results and discussion The mean surface soil concentrations of 137 Cs and 210 Pb ex were significantly different between soil erosion classes as hypothesised. Weighting surface soil from the high erosion class more heavily increased the estimated proportion of river sediment contributed from surface soil, by 35 % larger than if surface soil sampling was confined to low erosion areas. Stratified sampling and weighting by erosion rate is of greater importance in river basins with large gradients in soil erosion and where surface soil contributes substantially to river sediment. Surface soil contributed 6 % to fine sediment at the basin outlet and 0-14 % in major tributaries, which was somewhat lower than in a prior study probably due to recent above-average rainfall increasing vegetation ground cover. Conclusions Surface soil sampling for source tracing using fallout radionuclides should be stratified by erosion rate. The tracer properties of high erosion areas should be weighted more heavily than low erosion areas in source mixing models. If comprehensive sampling cannot be afforded, then sampling should be biased towards more highly eroding areas. The approach should be considered for other source tracers whose properties may co-vary with soil erosion rate. Fine sediment delivered from the Burdekin River basin to the Great Barrier Reef lagoon in recent decades was predominantly derived from gully erosion, streambank erosion and rilled and scalded areas on hillslopes.

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Section: Discussionmentioning

confidence: 99%

Sediment source tracing with stratified sampling and weightings based on spatial gradients in soil erosion

et al. 2015

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“…Further research, linking process understanding, derived from field data, with hill-slope and catchment models, is critical for transferring the results of this study to other rangeland areas in northern Australia. It is also critical for the scenario modelling that currently occurs as part of the Great Barrier Reef Water Quality Plan (Carroll et al 2012).…”

Section: Areas Of Further Researchmentioning

confidence: 99%

Can changes to pasture management reduce runoff and sediment loss to the Great Barrier Reef? The results of a 10-year study in the Burdekin catchment, Australia

Bartley¹,

Corfield²,

Hawdon³

et al. 2014

Rangel. J.

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Excess sediments from agricultural areas are having a detrimental impact on the Great Barrier Reef, and threaten the long-term viability of rangeland grazing. Changes to grazing management have been promoted as a mechanism for reducing excess sediment loss from grazed rangelands. This paper summarises the results of a 10-year study (2002–11) on a property in the Burdekin catchment that investigated the role of reduced stocking rates and rotational wet season resting on hill-slope and catchment runoff and sediment yields. Ground cover and pasture biomass were evaluated using on-ground surveys and remote sensing. During this study, average ground cover increased from ~35 to ~80% but pasture biomass was low due to the dominance of Bothriochloa pertusa (77% of composition). The percentage of deep-rooted perennial species increased from ~7% of pasture composition in 2002 to ~15% in 2011. This is still considerably lower than the percentage that occupied this property in 1979 (~78%). The increased ground cover resulted in progressively lower hill-slope runoff coefficients for the first event in each wet season, but annual catchment runoff did not respond significantly to the increasing ground cover during the study. Hill-slope and catchment sediment concentrations did decline with the increased ground cover, yet catchment sediment yields increased proportionally to annual runoff due to the contribution of sub-surface (scald, gully and bank) erosion. This study has demonstrated that changes to grazing management can reduce sediment concentrations leaving B. pertusa-dominated pastures, as B. pertusa is an effective controller of surface erosion. To further reduce the runoff that is fuelling gully and bank erosion, the proportion of deep-rooted native perennial grasses needs to be increased. It is argued that more than 10 years will be required to restore healthy eco-hydrological function to these previously degraded and low productivity rangelands. Even longer timescales will be needed to meet current targets for water quality.

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“…Under the Paddock to Reef program (Carroll et al 2012), a trial to assess the impact of a range of land management practices on productivity and off-farm water quality was conducted in the Burnett-Mary catchment, which discharges into the southern GBR lagoon. A sugarcane plant crop was managed using four different sets of practices.…”

Section: Carbon Losses In Runoff From Sugarcane Farming Systems In Somentioning

confidence: 99%

Carbon losses in terrestrial hydrological pathways in sugarcane cropping systems of Australia

Nachimuthu¹,

Bell²,

Halpin³

2016

Journal of Soil and Water Conservation

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A Paddock to reef monitoring and modelling framework for the Great Barrier Reef: Paddock and catchment component

Cited by 100 publications

References 60 publications

Sediment source tracing with stratified sampling and weightings based on spatial gradients in soil erosion

Sediment source tracing with stratified sampling and weightings based on spatial gradients in soil erosion

Can changes to pasture management reduce runoff and sediment loss to the Great Barrier Reef? The results of a 10-year study in the Burdekin catchment, Australia

Carbon losses in terrestrial hydrological pathways in sugarcane cropping systems of Australia

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