scholarly journals 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

2014 ◽  
Vol 36 (1) ◽  
pp. 67 ◽  
Author(s):  
Rebecca Bartley ◽  
Jeff P. Corfield ◽  
Aaron A. Hawdon ◽  
Anne E. Kinsey-Henderson ◽  
Brett N. Abbott ◽  
...  
Keyword(s):  
Great Barrier Reef ◽  
Ground Cover ◽  
Bank Erosion ◽  
Grazing Management ◽  
Barrier Reef ◽  
Wet Season ◽  
Sediment Yields ◽  
Hill Slope ◽  
Sediment Loss ◽  
Catchment Runoff

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.

Corrigendum to: 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

2014 ◽  
Vol 36 (3) ◽  
pp. 311
Author(s):  
Rebecca Bartley ◽  
Jeff P. Corfield ◽  
Aaron A. Hawdon ◽  
Anne E. Kinsey-Henderson ◽  
Brett N. Abbott ◽  
...  
Keyword(s):  
Great Barrier Reef ◽  
Ground Cover ◽  
Bank Erosion ◽  
Grazing Management ◽  
Barrier Reef ◽  
Wet Season ◽  
Sediment Yields ◽  
Hill Slope ◽  
Sediment Loss ◽  
Catchment Runoff

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.

Turbidity in the northern Great Barrier Reef lagoon in the wet season, March 1989

1994 ◽  
Vol 45 (4) ◽  
pp. 585 ◽  
Author(s):  
LJ Hamilton
Keyword(s):  
Great Barrier Reef ◽  
Attenuation Coefficient ◽  
Quantitative Relation ◽  
Barrier Reef ◽  
Wet Season ◽  
Secchi Disc ◽  
Reef Lagoon ◽  
Secchi Disc Depth ◽  
Beam Attenuation ◽  
Beam Attenuation Coefficient

In 1989, a typical wet season was experienced in northern Queensland, with low winds and long calm periods. Turbidity in upper waters of the Great Barrier Reef lagoon broadly had a simple distribution that could be modelled from bottom depth contour values alone, without introducing wind speed or bottom type. In the absence of major storm and cyclone events, this result appears to be general, based on the similarity between March 1989 survey data and Secchi disc climatology. The simple distribution arises because the main turbidity sources are riverine discharges, with little entrainment of bottom sediment into the upper column, except in shallower waters. Fresh, highly turbid riverine influxes are generally confined close inshore, with salinity and Secchi contours parallel to shore, forming cross-shelf gradients. A semi-quantitative relation was found between sea surface colour and Secchi disc depth. Examination of nephelometric turbidity stratification showed that satellite and Secchi data should be more useful for subsurface turbidity inference between Cooktown and Innisfail than in Princess Charlotte Bay, with horizontal and vertical stratifications, respectively, observed in those areas. Highest nephelometric turbidity was seen from Cooktown to Innisfail. Beam attenuation coefficient in oceanic waters outside the reef appeared to be dominated by absorption, with lagoon waters influenced by scattering. A method is suggested to enable approximate transfer of beam attenuation coefficient measured by a transmissometer operating at a single wavelength to beam attenuation coefficient at other wavelengths, using coincident measurements of Secchi disc depths made with filters.

Economically viable land regeneration in Central Queensland and improved water quality outcomes for the Great Barrier Reef

2011 ◽  
Vol 33 (3) ◽  
pp. 267 ◽  
Author(s):  
M. Star ◽  
P. Donaghy ◽  
J. Rolfe
Keyword(s):  
Great Barrier Reef ◽  
Ground Cover ◽  
Scientific Data ◽  
Barrier Reef ◽  
Sediment Loads ◽  
Land Condition ◽  
Sediment Reduction ◽  
Grazing Lands ◽  
The Impact ◽  
Land Types

The impact of excessive sediment loads entering into the Great Barrier Reef lagoon has led to increased awareness of land condition in grazing lands. Improved ground cover and land condition have been identified as two important factors in reducing sediment loads. This paper reports the economics of land regeneration using case studies for two different land types in the Fitzroy Basin. The results suggest that for sediment reduction to be achieved from land regeneration of more fertile land types (brigalow blackbutt) the most efficient method of allocating funds would be through extension and education. However for less productive country (narrow leaved ironbark woodlands) incentives will be required. The analysis also highlights the need for further scientific data to undertake similar financial assessments of land regeneration for other locations in Queensland.

Wet season fine sediment dynamics on the inner shelf of the Great Barrier Reef

2008 ◽  
Vol 77 (4) ◽  
pp. 755-762 ◽  
Author(s):  
Eric Wolanski ◽  
Katharina E. Fabricius ◽  
Timothy F. Cooper ◽  
Craig Humphrey
Keyword(s):  
Great Barrier Reef ◽  
Fine Sediment ◽  
Sediment Dynamics ◽  
Barrier Reef ◽  
Wet Season ◽  
Inner Shelf

Effect of terrestrial and marine humics on copper speciation in an estuary in the Great Barrier Reef Lagoon

1988 ◽  
Vol 39 (1) ◽  
pp. 19 ◽  
Author(s):  
GB Jones ◽  
FG Thomas
Keyword(s):  
Great Barrier Reef ◽  
Humic Substances ◽  
Coastal Waters ◽  
River Estuary ◽  
Barrier Reef ◽  
Wet Season ◽  
Reef Lagoon ◽  
Copper Speciation ◽  
High Concentrations ◽  
Monsoonal Season

Studies carried out over several years on a tropical estuary, the Ross River Estuary, have shown that copper speciation is influenced by both terrestrial and marine humic substances. While terrestrial humic substances are mobilized by high freshwater runoff in the monsoonal season, Trichodesmium blooms mobilize high concentrations of marine humics to the inshore zone and increase labile forms of copper. The marine humics are more soluble than the terrestrial humics and persist in coastal waters of the Great Barrier Reef lagoon for many months prior to the wet season.

Impact of wet season river flood discharge on phytoplankton absorption properties in the southern Great Barrier Reef region coastal waters

2017 ◽  
Vol 196 ◽  
pp. 379-386 ◽  
Author(s):  
Nagur Cherukuru ◽  
Vittorio E. Brando ◽  
David Blondeau-Patissier ◽  
Phillip W. Ford ◽  
Lesley A. Clementson ◽  
...  
Keyword(s):  
Great Barrier Reef ◽  
Coastal Waters ◽  
Barrier Reef ◽  
Wet Season ◽  
Absorption Properties ◽  
Flood Discharge ◽  
River Flood ◽  
Phytoplankton Absorption

Spatio-temporal variability in surface Chlorophyll distribution in the Central Great Barrier Reef as derived from CZCS imagery

1990 ◽  
Vol 41 (3) ◽  
pp. 313 ◽  
Author(s):  
AJ Gabric ◽  
P Hoffenberg ◽  
W Boughton
Keyword(s):  
Great Barrier Reef ◽  
Temporal Variability ◽  
Large Scale ◽  
Nutrient Loads ◽  
Barrier Reef ◽  
Phytoplankton Abundance ◽  
Wet Season ◽  
Chlorophyll Distribution ◽  
Consistent Feature ◽  
Spatio Temporal

A series of Coastal Zone Colour Scanner (CZCS) images has been used to compare the surface phytoplankton variation in the central Great Barrier Reef waters over the period 1979-81. Near- concurrent field data have been obtained for all the scenes so that approximate chlorophyll concentrations have been applied in the image classification. A consistent feature in the dry-season chlorophyll distribution is a cross shelf gradient with high chlorophyll levels inshore and lower levels in the mid-lagoonal waters increasing to higher concentrations in the reef matrix. The effects of higher nutrient loads in the wet season are also evident, although correlation between riverine discharge and phytoplankton abundance in the lagoon is problematic. In fact, a large scale 'bloom' event occurs before the start of the 1980-81 wet season and may be related to wind resuspension of sedimentary nutrients.

Improved grazing management practices in the catchments of the Great Barrier Reef, Australia: does climate variability influence their adoption by landholders?

2015 ◽  
Vol 37 (5) ◽  
pp. 507 ◽  
Author(s):  
Megan Star ◽  
John Rolfe ◽  
Peter Long ◽  
Giselle Whish ◽  
Peter Donaghy
Keyword(s):  
Great Barrier Reef ◽  
Management Practices ◽  
Grazing Management ◽  
Expected Returns ◽  
Economic Modelling ◽  
Barrier Reef ◽  
Financial Returns ◽  
Risk And Uncertainty ◽  
Agricultural Producers ◽  
Climate Cycle

The declining health of the Great Barrier Reef from diffuse source pollutants has resulted in substantial policy attention on increasing the adoption of improved management practices by agricultural producers. Although economic modelling indicates that many improved management practices are financially rewarding, landholders with dated management practices remain hesitant to change. This research involved bio-economic modelling to understand the variance in private returns for grazing enterprises across a climate cycle. Results show that financial returns to landholders can vary substantially across different 20-year periods of a climate cycle, demonstrating that the variability in expected returns may be an important reason why landholders are cautious about changing their management practices. Although previous research has separately identified financial returns and attitudes to risk and uncertainty of landholders as key influences on decisions concerning adoption of improved management practices, this research demonstrates that it is the interaction between these factors that is important to understand when designing policy settings.

Spatial and temporal patterns of near-surface chlorophyll a in the Great Barrier Reef lagoon

2007 ◽  
Vol 58 (4) ◽  
pp. 342 ◽  
Author(s):  
J. Brodie ◽  
G. De'ath ◽  
M. Devlin ◽  
M. Furnas ◽  
M. Wright
Keyword(s):  
Great Barrier Reef ◽  
Chlorophyll A ◽  
Agricultural Development ◽  
Monitoring Program ◽  
Barrier Reef ◽  
Spatial And Temporal Patterns ◽  
Wet Season ◽  
Near Surface ◽  
Nutrient Delivery ◽  
Inshore Waters

Surface chlorophyll a concentrations in the Great Barrier Reef (GBR) lagoon were monitored at individual stations for periods of 6 to 12 years. The monitoring program was established to detect spatial and temporal changes in water quality resulting from increased loads of nutrients exported from the catchments adjoining the GBR. Sampling occurred monthly at up to 86 sites that were located in transects across the width of the continental shelf. In the central and southern GBR (16–21°S), there was a persistent cross-shelf chlorophyll a gradient, with higher concentrations near the coast. No cross-shelf gradient was observed in the far northern GBR (12–15°S). Mean chlorophyll a concentrations in the far northern GBR (0.23 µg L–1) were less than half those in the south and central GBR (0.54 µg L–1). Chlorophyll a varied seasonally within regions, with mean summer-wet season (December–April) concentrations ~50% greater than those in the winter-dry season (May–November). Sub-annual, inter-annual and event-related variations in chlorophyll a concentrations were observed in several zones. Multi-year patterns in concentrations suggest that relatively short (5–8 years) time series may give spurious estimates of secular trends. Higher chlorophyll a concentrations in inshore waters south of 16°S were most likely related to the levels of river nutrient delivery associated with agricultural development on adjacent catchments.

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