ausgeo - ga.gov.auausgeo news december 2004 issue no. 76 editors jeanette holland, steve ross...

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AUSGEOnewsDecember 2004 ISSUE No. 76

Also: Sal inity management , geosequestration explained, Gawler seismic study. .

&Finding a balanceFinding a balance

Green clean&

A U S G E O N e w sDecember 2004 Issue no. 76

Editors Jeanette Holland, Steve Ross

Graphic Designer Katharine Hagan

This publication is issued free ofcharge. It is published four times ayear by Geoscience Australia.

The views expressed in AusGeoNews are not necessarily those ofGeoscience Australia, or the editors,and should not be quoted as such.Every care is taken to reproducearticles as accurately as possible, butGeoscience Australia accepts noresponsibility for errors, omissionsor inaccuracies.

© Commonwealth of Australia 2004ISSN 1035-9338

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The cover image is a composite of estuaries insouthern New South Wales. In many Australiancoastal waterways plant growth is stimulated bynutrients that come from the catchment.Something is happening at the bottom of thesewater-ways or in their water that allows them tohandle big sediment-nutrient loads withoutthreatening ecosystem health. These factors arediscussed in this issue of AusGeo News.

CONTENTS

Comment 3

Geoscience essential in salinity management 4

The changing face of temperate waterways 8

Geosequestration of carbon dioxide

—some frequently asked questions 12

New directions for National Mapping Division 15

How estuaries cope with nutrients 17

Coastal CRC project update 20

In brief….

Shifting sands update 22

Australia’s mineral exploration ranking

continues to slip 23

Gawler seismic study 24

Seamless topographic database 25

Events calendar 25

100K scale mapping pilot to help emergency

management 26

Agreement signed between Australian Greenhouse

Office and Geoscience Australia 26

Product news 27

AusGEO News 76 December 2004 3

N E I L W I L L I A M SCEO Geoscience Australia

As Australia's national agency for geoscience research and geospatialinformation, Geoscience Australia holds historical and near real-time satelliteimagery that helps Government and industry monitor and managedeforestation, salinity, erosion, urban sprawl, agricultural productivity andnatural disaster damage resulting from droughts, floods and bushfires. Ournational coverage of topographic information ensures that reliable data isavailable to support a broad range of Government programs. GeoscienceAustralia’s advice on Australia’s maritime boundaries assists in theenvironmental management and surveillance of Australia’s vast oceanterritory, especially with respect to oil spills and illegal bilge dumping. Arecent internal review of Geoscience Australia's national mapping and remotesensing activities recommends enhancing access to ‘public good’ high qualitysatellite and other spatial data to support the increasingly diverse needs ofgovernment and the private sector. A significant step forward in this directionis the recent agreement to make the Japanese ASTER satellite data availablethrough ACRES.

This issue of AusGeo News, the first in the electronic-only format,contains articles illustrating the important role geoscience is playing incontributing to a number of environmental issues of national importance. Asusual it also contains announcements of new results and products of interestto a wide range of users in the minerals, petroleum, and spatial informationsectors as well as the land and marine environments. The first results fromthe 2003 seismic reflection survey of the Gawler Craton in the vicinity of thegiant Olympic Dam copper-gold-uranium deposit will be of interest tomineral exploration companies as it provides the first 3-dimensional image ofthis major mineral system.

Of particular concern to the minerals sector is the continued decline inAustralia's share of global mineral exploration budgets despite an increase inactivity.

The salinisation of Australia's waterways and land is a major challenge asrecognised by the National Action Plan for Salinity and Water Quality.Geoscience Australia, through the CRC for Landscape Environments andMineral Exploration (CRC LEME), in collaboration with a number of stateagencies and CSIRO, has recently completed a number of projects thatdemonstrate the value to regional natural resource management of airbornegeophysics. Airborne electromagnetic surveys, in particular, can be integratedwith other geoscientific data in groundwater and salinity mapping and indetermining controls on groundwater and salt movement.

Rising levels of greenhouse gas inthe Earth's atmosphere is an issue ofboth national and internationalconcern. Geosequestration of carbondioxide is one proposed method tomanage emissions from energyproduction. Geoscience Australia,through the Cooperative ResearchCentre for Greenhouse GasTechnologies (CO2CRC), is engaged ingeological studies to evaluate potentialsites for the long-term storage ofcarbon dioxide.

Managing highly sensitive parts ofAustralia’s marine environment is alsoa national priority. Estuaries and thecoastal waterways in temperateAustralia contain important habitatsbut are especially at risk because theyare heavily used by coastalcommunities. The interplay ofgeomorphology and sedimentologycontrols the shape of estuaries andgoverns their vulnerability to humaninterference. The exchange ofnutrients between estuarine water andsediments also influences the health oftheir ecosystems. The OzEstuariesdata-base, developed by GeoscienceAustralia and now available on-line,contains new maps of sedimentaryhabitats for 73 near-pristine estuaries.It will assist in monitoring the healthof the habitats in these ever-changingbut important systems.

I hope you enjoy reading theDecember issue and wish you all thevery best for the 2004 festive season.

NH4+

Comment

4 December 2004 AUSGEO News 76

The salinisation of Australia’swaterways, groundwater resourcesand land is recognised at all levelsof government and by rural andregional stakeholders as a majornational challenge with profoundeconomic, social and policyimplications.

It is also recognised that large-scale revegetation of catchments totackle this issue is in many casesimpracticable, and that salinitymanagement will need to betargeted to protect assets andmaximise the return on investments.

To assist with these objectives,the Cooperative Research Centre forLandscape Evolution and MineralExploration (CRC LEME), incollaboration with a number of stateagencies and CSIRO, has recentlyfinalised a number of projects inSouth Australia and Queensland.The aim of these projects was toassess the effectiveness of airbornegeophysics and integratedgeoscience approaches for salinitymapping and management in arange of landscape, climate zoneand land use settings. These prioritystrategic projects were identifiedunder the Salinity Mapping andManagement Support Program(SMMSP), and were funded underthe auspices of the National ActionPlan for Salinity and Water Quality(NAPSWQ).

These projects differed inapproach from previous studies, asthey were set up specifically toevaluate the use of airbornegeophysics and integratedgeoscience to address specific land

management questions, as part of broader regional natural resourcemanagement strategies. The projects involved a staged and targetedapproach, working within natural resource management policy frameworks,in close collaboration with local stakeholders.

Generally, previous salinity investigations involving airborne geophysicshave been effective at knowledge generation, but ineffective in deliveringoutcomes for salinity management. This is partly because a betterunderstanding of the sub-surface is only a first step in delivering outcomes,and because geophysics is only adding value to some of the knowledgealready acquired.

Most of the SMMSP projects involved an integrated geoscience approachwhich combined regolith landscape and bedrock geological studies withairborne and/or ground and borehole geophysics, hydrogeology andhydrogeochemistry, to underpin outputs largely at sub-catchment scale. Acommon theme linking the projects was that they were not restricted to‘mapping salt’ but were more concerned with gaining an understanding ofthe groundwater and salinity systems that prescribe water and salinitymanagement practices. CRC LEME’s contribution to these projects includedmapping and understanding the nature and distribution of regolith materialsthrough which groundwater and salt move, and hydrogeochemical studiesto better understand the processes and rates of salt mobilisation.

GEOSCIENCE ESSENTIAL IN

Recently completed projects in South Australia and Queensland havedemonstrated the value of using airborne geophysics within anintegrated geoscience approach to mitigating salinity in Australia.

salinitymanagement

salinitymanagement

salinitymanagement

Figure 1. Schematic cross-section through the Riverland project areashowing the relationship between the aquitard (Blanchetown Clay) andunderlying groundwater in the Loxton-Parilla Sands aquifer.

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South Australian projectsProjects were completed in five geographic areas: Riverland, Tintinara, AngasBremer Hills, Angas Bremer Plains, and Jamestown. The salinity issues ineach of these areas differed significantly, and the project areas range overcomplex erosional and depositional regolith landscapes. The projectsinvolved collaboration with the South Australian Department for Land, Waterand Biodiversity Conservation, CSIRO Land and Water, and the Bureau ofRural Sciences (BRS).

In the Riverland project, CRC LEME produced maps of near-surface claymaterials and the underlying aquifer. An important component of the projectentailed the calibration and inversion of Helicopter Frequency DomainElectromagnetic (HEM) data to derive datasets which are being used toidentify areas of groundwater recharge in the Riverland area of the lowerMurray. One of the factors considered in predicting rates of increase inMurray River salinity is increases in aquifer recharge in the Riverland area asa consequence of land clearing. Specifically, the near-surface fine texturedunit known as Blanchetown Clay, an aquitard which reduces recharge to thelower aquifer, was mapped (figure 1). The Blanchetown Clay is characterisedby elevated conductivities relative to the overlying and underlyingsedimentary units (figure 2a). The derived maps of clay thickness were used,in conjunction with other critical data, as a basis for estimating rates ofdrainage through the unsaturated zone and for predicting groundwaterrecharge. The map of clay thickness was used as an input into a

groundwater modelling exercise todetermine the effects of proposedrecharge reduction options inmitigating River Murray salinity.Outputs from this project arecontributing to improved regionalplanning tools including:• Improved recharge maps for

underlying groundwatersystems up to 100 years intothe future, using theBlanchetown Clay map andrecent developments in soilhydrology

• A floodplain attenuation modelthat simulates the impact onsalt loads to the River Murray,and impact of irrigationdevelopment on the floodplain

• Improvements to modelscommonly used in land-use andsalt assessments (SIMPACTirrigation planning model) andBorder-to-Lock 3 MODFLOW(recharge and floodplainattenuation model).

Even for data-rich areas, theconstrained inversion of the HEMdata was essential for accuratelymapping the clay layer. Withoutspatial constraints on depth togroundwater, groundwater salinity,and petrophysical (electrical)responses of the principalsedimentary units, we would havebeen unable to successfullygenerate a useful product. Principaloutcomes of the project were:• Development of new

sedimentological models for theBlanchetown Clay andunderlying Loxton-Parilla Sand.

• Successful staged use ofairborne and groundgeophysics for salinitymanagement.

• Development of a newconstrained inversion techniqueto map clay distribution.

Figure 2. Riverland project (a) Comparison of clay thickness estimates from widelyspaced boreholes (left) with thickness estimated from HEM (right). (b) HEM apparentconductivity composite images showing a plan view of strand lines in the Loxton-Parillasand aquifer (left) and complexity in distribution of clays (right).

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(b)

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• Geophysical interpretationswhich contribute to salinitymanagement plans andrecharge reduction schemes.Clay thickness maps allow newestimates of aquifer rechargefor dryland agriculture forpresent and future years (2023,2053 and 2103). Newhydrogeological models(MODFLOW and SIMPACT)were developed by CSIRO andthe South Australiandepartments for Land, Waterand Biodiversity Conservation,and Environment and Heritageusing these data. They providethe necessary spatialinformation to achieve thegreatest impact on river salinitythrough revegetation.

• Salinity inputs to the MurrayRiver can be reduced.

Also in the Riverland area, saltinterception schemes (SIS) beingdeveloped at Loxton andBookpurnong on the Murray River,employ borefields in the LoxtonSands aquifer (figure 2b). Theirpurpose is to remove salinegroundwater that rises in moundsbeneath irrigated areas. CRC LEMEcontributed significantly to thedesign of the schemes throughdevelopment of a newsedimentological model atBookpurnong that defines lateraland vertical facies in the mainaquifer systems. This model isbased on borehole geology, groundand airborne geophysics, andsedimentological analysis of LoxtonSands and underlying BookpurnongSands. This is a precursor to apredictive groundwater hydraulicmodel.

Definition of thesedimentological characteristics ofthe principal aquifer system—theLoxton Sands, has beenproblematic. Narrow zones of hightransmissivity, characterized byreduced electrical conductivity atthe watertable, are the target forground TEM geophysical traverses.These are elements of a beach-barrier strandline sequence acrossthe basin that developed in thePliocene. Constrained inversionsfrom helicopter electromagneticdata have helped to better definethe geometry of this sedimentarysystem, and together with ahydrogeological interpretation allowan informed development andoperation of the Loxton Sands saltinterception scheme.

Lower Balonne (Queensland)This project, in southern Queensland (figure 3), involved acquisition of 8,000square kilometres of airborne electromagnetic (AEM) data, the largest surveyin Australia acquired for salinity investigations. The area is an importantcotton irrigation district where there is debate over land cropping practices,water allocation and salinity risks. The project was undertaken in conjunctionwith the Queensland Department of Natural Resource Management(QDNRM), the Bureau of Resource Sciences (BRS), local catchment managersand cotton irrigators, and was funded under the National Action Plan forSalinity and Water Quality (NAPSWQ). The project evaluated the use ofairborne geophysics (principally gamma radiometrics and time-domain AEM),for mapping surficial floodplain deposits and groundwater systems. Theproject is novel in its application of AEM technology to large inland fluvialfloodplains, in an area where the salt distribution is unknown, and thehydrogeology is dominated by regional groundwater flow systems.

Highlights of the project included: • A new method for constrained inversions of time-domain AEM data in

areas of conductive basement lithologies (this had only been possiblebeforehand in areas with electrically resistive basement).

• A new model of landscape evolution was developed by integratinggeophysics and biophysical datasets. The area is characterised bycomplex regolith architecture, a fault-controlled palaeo-valley at depththat hosts a fresh water aquifer, and saline aquifers near the surface. Thecompartmentalised sub-surface architecture is not evident from thesurface landscape.

• The three-dimensional (3D) regolith model, when integrated withhydrogeochemical data, allows surface-groundwater interactions andgroundwater movements to be modelled (figure 4). The integratedgeoscience approach reveals apparently disconnected aquifers in nestedgroundwater flow systems concealed beneath the low relief landscape.Groundwater flow paths are different in each of the three majorlandscape zones.

• Integrated datasets that map near-surface groundwater tables, and detectwater gain and loss points in the Lower Balonne river system.

Figure 3. Lower Balonne airborne geophysicsevaluation project location map(superimposed on digital elevation model).

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The main findings of the project include:• Airborne geophysics,

particularly AEM, significantlyimproves the understanding ofsalinity risk and water security,in areas where there is a lackof data. Such datasets must beintegrated with biophysicaldata (including bedrockgeology and regolith data), andhydrogeological andhydrogeochemical data, inorder to provide the bestinformation on rates ofmovement for groundwaterand salt.

• Integrated geoscience datasetsprovide a better understandingof the distribution of soil andregolith properties, salt storesand groundwater quality. Thisknowledge highlights areas indanger of salinisation if currentpractices are maintained.

• Newly identified land andgroundwater managementzones will enable modificationof land practices to reducesalinity risks. This knowledgeshould also lead to moreefficient water management.

• An enhanced understanding ofdynamic water balance for thecatchment.

ConclusionsPreliminary external assessments of outputs from these projects have beenvery positive. Overall, these projects have demonstrated the value of anintegrated geoscience approach for salinity management that incorporatesairborne geophysics. Particular importance was attached to ensuring thatgeophysical data could provide a product of value, and how that productcould be incorporated into the implementation of an existing managementstrategy.

Specific lessons from the South Australian and Queensland projects include:• AEM is an important aid in salinity management, particularly where there

are well defined targets and applications for the derived products. It isalso of great value in areas where there is limited understanding ofgroundwater and salinity systems.

• While focus on a specific management objective or target is important, thedesign of geophysical surveys should also consider other targets that maybe useful in salinity management. We need to be prepared for theunexpected benefit, but this should not be the driver of the survey.

• AEM is not limited to mapping of salt, but can provide invaluable insightsinto mapping groundwater and the regolith and bedrock materials thatinfluence and/or control groundwater and salt movement.

• The success of constrained inversion of AEM data in both the Riverlandand Lower Balonne projects is dependent on data availability and thescale of regolith landscape elements and the scale of hydrogeologicalvariability—this approach is facilitated by a wealth of existinghydrogeological information—the more data, the more accurate theproduct.

• The assertion that where a large pool of land-management data exists atan appropriate scale, airborne geophysics is unlikely to add value, isincorrect. On the contrary, AEM data should always be examined, wherethe means exist, to translate derived information into something of value.

• The value of airborne geophysical (particularly AEM) data increases withthe value of the asset. In lower-value areas serious consideration must begiven to geophysical inputs in order to minimise costs. In areas withlimited hydrogeological information, there may need to be moreinvestment in ground programs, to get full value from AEM datasets.

• In the planning of a project, it is important to ensure that all relevant dataare used in developing salinity management plans.

• Products derived from airborne geophysics only have value if theycontribute to the planning of economic activities.

For further information phone Ken Lawrie on +61 2 6249 9847 or e-mail [email protected]

Figure 4. Oblique-view AEM cross-sections through the LowerBalonne project area. Boreholedata is used to assist withinterpretation of AEM data toinform on salinity and groundwaterdistribution and movements.

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When glaciers and ice sheets melted, sea level rose and flooded river valleysand low lying areas of the continental margin. About 7,000 years ago thewaterways we now see around the coastline began to take shape. Australia’scoastline is about 37,000 km in length with more than 1000 waterwaysidentified and classified as a part of the National Land and Water ResourcesAudit.1,2

These waterways have been shaped by the erosion of our continent andwaves and tides—two very powerful coastal forces. The shapes andbiophysical characteristics of our tropical waterways such as habitat size,and water quality (flushing and turbidity/brown water) are controlledprimarily by the rates of sediment and nutrient inputs and dominant tidalenergies. Tropical coastal waterways tend to be well-flushed with highturbidities, and are dominated by very large intertidal mudflat areas andmangrove forests. In contrast, the changing shapes and biophysicalcharacteristics of waterways in temperate Australia are controlled primarilyby the different rates of sediment and nutrient discharges and interactionswith high wave energies at the coastline. The classifications and conditionsof Australia’s coastal waterways are shown at www.OzEstuaries.org

Evolution in temperate coastal waterwaysThe wave dominated systems of temperate Australia have been classifiedinto several different types such as immature and partially-filled estuaries(and coastal lakes), river dominated estuaries (deltas), strand plains andlagoons. These systems comprise a variety of habitats and biophysicalproperties which continually evolve and change shape as they infill withsediments.

Immature and part ial ly f i l led estuariesImmature and partially-filled wave-dominated estuaries are characterised bya large central basin and a constricted entrance, limiting flushing andexchange with the sea. Tidal excursion is inhibited and these systems havesmall intertidal areas. The effects of infilling and changing tidal ranges onhabitats during the evolution of temperate wave-dominated waterways areshown in figure 1.

Analysis of data from the OzEsturies database reveals that the centralbasin comprises about 40 per cent, the intertidal flats and salt-marsh about10 per cent, with mangroves representing about three per cent of the totalareas of these systems.3 Diatomaceous phytoplankton grow throughout andare dominant in the central basin and channels, while seagrass communitiesand other benthic algae inhabit the shallow margins. The relative areas ofthese different habitats and ecosystems are illustrated in figure 2 andimmature estuaries are shown to the left of this figure.

With increasing sediment discharge, immature estuaries become partiallyfilled, the depth shallows and a large proportion of the sediments within thecentral basin emerge into the photic zone where light penetrates. As a resultthe abundance of seagrass and other benthic plant communities increase asmore surface area of bottom sediments are exposed to light (figures 1 & 2).

Figure 1. Conceptualization ofestuarine shape, tidal penetrationand ecosystem change duringestuarine infilling.

THE CHANGING FACE OF temperate coastal waterwaysH A B I T A T S A N D W A T E R Q U A L I T Y

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temperate coastal waterways

The habitats in partiallyfilled systems may change easilyin response to externalperturbations such as increasedsediment inputs from thecatchment (figure 2). Figure 3shows a satellite image ofimmature-to-partially filledestuaries; the large central basinand the restricted entrances arekey physical features.

Figure 2. Changes in relative habitat abundances (water areas and phytoplankton,benthic plants and intertidal ecosystems) during estuarine infilling and evolution:immature estuaries to the left and river dominated estuaries (deltas) to the right.


River-dominated estuaries (deltas)Continual erosion of the catchment sediments will cause the central basin tofill. During this process (known as increasing maturity) channels increase,the entrance widens, and there is a greater connectivity with the sea and thetides penetrate further into the estuary (figure 1).

Because of the increasing tidal excursion the areas of intertidal mudflats,salt-marsh and mangrove habitats increase (figure 2). Analysis of the habitatareas of river-dominated estuaries show that the central basin comprisedonly <1 per cent, the intertidal mudflats and salt-marsh areas each comprisedabout 20 per cent, and the mangrove forests about 30 per cent of the areasof these systems.3 . Therefore, with sediment infilling, estuaries mature intodeltas and during this transition the mangrove areas increase about tenfold,while the intertidal flats and salt-marsh areas nearly double. Eventually,seagrasses (and other shallow-water benthic communities) are replaced bymangroves. These features are summarised in figures 1 & 2, with thecharacteristics of the deltas shown on the right of figure 2.

Figure 4 is an image of a river dominated estuary and the key physicalfeatures are the elongate nature of the system with channel developmentand an increased connectivity to the sea.

Water qualityWater quality deteriorates when estuaries become eutrophied. Eutrophicationis the process of nutrient enrichment which can manifest itself in severalways including increased incidences of nuisance and toxic algal blooms(which can sometimes be harmful to human health), epiphytic growth onseagrass leaves (which result in the die-back of seagrass meadows), andprolific macro-algal growth which can sometimes clog waterways. Inaddition, when this plant material dies and accumulates on the sediments, itsdegradation can result in oxygen depletion from the water, fish-kills andsometimes the production of foul-smelling hydrogen sulphide or rotten egg gas.

Nitrogen, phosphorus and silicon are essential nutrients which stimulateplant growth, but nitrogen (N) is thought to be the most important nutrientcontrolling the potential eutrophication of temperate waterways. Sedimentsand nutrients from the catchment are the greatest threat to coastal waterquality.4 Eutrophication results when nutrient concentrations in the estuarinewaters become too high. Several processes can remove nutrients fromestuaries to maintain low nutrient concentrations and limit eutrophication.These include flushing to the sea, burial in the sediments and denitrification,a microbial reaction (unique to nitrogen) found at the sediment-waterinterface.

Denitrification occurs in low-oxygen environments, usually just belowthe sediment surface in the top mm-to-cm of sediments. This is part of theprocess of degradation of organic matter in sediments where N fixed intoplants is converted into nitrogen gas. The gas escapes from the surficialsediments through the water column to the atmosphere and this process is avery important N-sink that reduces the concentrations of bio-available N incoastal waterways. Denitrification was responsible for removing N from PortPhillip Bay and controlling and limiting phytoplankton productivity.5

Figure 3. Satellite image of animmature-to-partially filled estuary.

Figure 4. Satellite image of a river-dominated estuary.

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Diatoms and denitr i f ication in immature andpartial ly f i l led estuariesImmature and partially filled estuaries, strand plains and ICOLLS(intermittently closed and open lakes and lagoons) with restricted entrancesare very efficient traps of sediment-bound and dissolved nutrients (figure 5).The most important process controlling bio-available nutrient concentrationsin these systems is denitrification. These features of immature-to-partiallyfilled estuaries are shown in figure 5.

Recent research has found that most of the nutrients are taken up intodiatomaceous phytoplankton—despite an apparent visual abundance ofmacro-algal growth. Diatoms are small microscopic single-celled organismswhich are formed during photosynthesis and require carbon, nitrogen,phosphorus and silicate to grow. They are most abundant in temperateclimates; an organic sheath surrounds a silicate frustule (hard part). Diatomssink rapidly to the sediments where they degrade. The degradation of thisorganic matter is enhanced by bioturbation and bio-irrigation—theburrowing and foraging activities of animals living in the sediments.

These processes facilitate denitrification and can limit the build-up ofbio-available N and thus maintain good water quality in these systems. Ifdiatom production is impeded significantly by limiting silicate supply toestuaries (such as by building dams and other impoundments on rivers andstreams), then the amount of N lost by denitrification in the sediments willbe reduced. The reason for this is because macroalgae thrive (displacingdiatoms) recycling N through the water column rather then the sedimentsthus avoiding the denitrification reaction. Bio-available-N, added from thecatchment, under these conditions, will accumulate in the water and result inan increased risk of eutrophication.

These processes are shown schematically in figure 6. Sensiblemanagement practices should maintain a healthy benthos and efficientdenitrification.

Denitr i f ication, mangroves, salt marshes andflushing in r iver-dominated estuariesWith increasing sediment-infilling, immature and partially filled estuariesbecome river-dominated (deltas) (see figure 1). Connectivity to the sea isincreased and flushing of sediments and water are enhanced and thesediment-nutrient trapping capacity reduced (figure 5). In time, the largewater areas and low energy environments of a central basin are replaced bychannels with a more vigorous circulation. Flushing is more important inmature estuaries than in immature estuaries (figure 5) helping to maintainlow concentrations of bio-available N which inhibits prolific plant growth.

Denitrification remains an important process but in river-dominatedestuaries, it is more important in channel-sediments, mangroves, intertidalflats and salt-marsh environments (figure 5).

Diatoms (even in mangrove sediments) remain an important vector totransport N to the sediments where it is lost because of denitrification.Research has shown that the denitrification process is very efficient inmangrove and intertidal flat sediments. Crabs and burrowing organisms arevery common and abundant in mangroves and mud-flats. These activitiesfacilitate the denitrification process by constantly turning over sediments,ventilating them with dissolved oxygen (which is rapidly consumed), andconstantly renewing surfaces facilitating the break down of organic matter.

When mangroves and intertidal habitats are lost (through dredging andinfilling to create housing and industrial estates), the natural cleansingcapacity of these systems is drastically reduced and most probably lostforever.

As a result they become more prone to eutrophication. Mangroves andintertidal habitats have long been highly valued, as they are known toaccommodate the nurseries of many of our common and popularrecreational fish-catches and crustacean hauls. Similarly, their capacity tosupport and sustain good water quality should also be recognised.

References.1. Heap AD, Bryce S, Ryan D,

Radke L, Smith C, Smith R,Harris PT & Heggie DT. 2001.Australian estuaries and coastalwaterways: A geoscienceperspective for improved andintegrated resourcemanagement. AustralianGeological Survey Organisation,record 2001/07.

2. Harris PT, Heap AD, BryceSM, Porter-Smith R, Ryan DA &Heggie DT. 2002. Classificationof Australian clastic coastaldepositional environmentsbased upon a quantitativeanalysis of wave, tidal and riverpower. Journal of SedimentaryResearch, 72: 858—870.

Figure 5. Changes in relative sedimentand nutrient trapping and flushingcharacteristics and nitrogen removalprocesses such as burial, anddenitrification in central basin, mangrove,salt-marsh and mudflat sediments.

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Figure 6. A schematic representation of the link between diatom formation in the water,degradation in the sediments and the important N-processes, including denitrification inthe sediments.

3. Heap AD, Bryce S & Ryan D.2004. Facies evolution ofHolocene estuaries and deltas:a large sample statistical studyfor Australia. SedimentaryGeology: 20041—17.

4. Zann LP. 1995. Our Sea, Ourfuture. Major findings of theState of the EnvironmentReport. Great Barrier ReefMarine Park Authority, forDept. of Environment, Sportand Territories, Ocean Rescue2000 Program.

5. Heggie DT, Skyring GW,Orchardo J, Longmore AR,Nicholson GJ, & Berelson WM.1999. Denitrification anddenitrifying efficiencies insediments of Port Philip Bay:direct determinations ofbiogenic N2 and N-metabolitefluxes with implications forwater quality. Marine andFreshwater Research, 50:589—596.

The Australian National Seismic Imaging Resource (ANSIR), a MajorNational Research Facility, is seeking bids for research projects forexperiments in 2005 and beyond.ANSIR operates a pool of state-of-the-art seismic equipment suitable forexperiments designed to investigate geological structure. ANSIR isoperated jointly by The Australian National University and Geoscience Australia.The equipment is available to all researchers on the basis of merit, asjudged by an Access Committee. Please note demand for the broad-bandequipment is very high and this should be taken into consideration inthe design of experiments. ANSIR provides training in the use of itsportable equipment and a field crew to operate its seismic reflectionprofiling systems. Researchers have to meet project operating costs.Applicants should consult the web site, www.rses.anu.edu.au/seismology/ANSIR/ansir.html for details of the equipment available, access costs,likely field project costs and the procedure for submitting bids. This siteincludes an indicative schedule of equipment for projects that arose fromprevious calls for proposals.Researchers seeking to use ANSIR equipment from the beginning of 2005should contact the ANSIR Director with regard to the formation ofresearch proposals.

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Enquires should be directed to:Prof. Brian KennettANSIR DirectorResearch School of Earth SciencesAustralian National UniversityCanberra ACT 0200Telephone +61 2 6125 4621Facsimile +61 2 6257 2737e-Email [email protected]

Call for RESEARCH PROPOSALSfor ANSIR experiments in 2005

beyond

For more information phone David Heggie +61 2 6249 9589or e-mail [email protected]

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Geoscience Australia is contributingto this research as one of theleading agencies in the CooperativeResearch Centre for GreenhouseGas Technologies(CO2CRC). TheCRC draws on the expertise ofresearch organisations anduniversities around Australia, andparticipants from the private sectorinclude petroleum, coal and powercompanies.

So in an attempt to clarify thesubject some frequently askedquestions are explained below:

What is geologicalsequestration?Geological sequestration is theprocess of capturing carbon dioxidefrom industrial processes such aspower generation and injecting itdeep underground for long termstorage in geological formations,thus preventing it entering theatmosphere and adding to thepotential for climate change causedby greenhouse gases.

Among the options beingconsidered for storage of carbondioxide are injecting it intodepleted oil and gas fields, deepsaline reservoirs or deepunmineable coal deposits.

Why do we need to store carbon dioxide?In the modern world we rely on electrical power to provide the quality oflife that we enjoy and that the developing world is aiming to achieve. Mostof the power used to meet our needs is derived from burning fossil fuels inpower stations. As renewable sources of energy are unlikely to be able tomeet that demand, the dependence on fossil fuels as our major energysource is unlikely to change in the near future.

The burning of fossil fuels releases carbon dioxide, which is the gas thathas contributed most to the greenhouse gas effect. Capturing the carbondioxide before it is emitted and storing it in the deep subsurface will help toreduce the impact of our use of energy.

The development of this technology in Australia will not only reduce ouremissions but also provide a lead to help the countries of the developingworld reduce their greenhouse gas output.

How can you store anything in sol id rock?Many sedimentary rocks, particularly sandstones, contain large volumes offluids held in microscopic voids or pores between the rock grains. Thesepores can be up to 30 per cent of the volume of the rock (figure 2). Wherethe pores are interconnected the rock has permeability, that is, fluids canmove through it.

Rocks of this type form the underground reservoirs. Under normalconditions the pores in the rocks are filled with water, but under specialconditions they may contain oil, natural gas (methane) or naturally occurringcarbon dioxide.

Many finer grained rocks such as clays also have high porosity, howeverthe pores are not interconnected and fluids cannot move through them, thatis, they are impermeable. These rocks act as seals or caps to the reservoirrocks

Over geological time, the weight of the overlying sediments graduallyreduces the porosity of both sandstones and shales until they are effectivelyimpermeable. Often, however, sandstones may still retain significant porosityand permeability at depths in excess of four kilometres.

Figure 1. Almost half of Australia’s carbon dioxide emissions come from stationarysources and could potentially be stored. Three-quarters of these sequesterableemissions come from power stations.

Geosequestration of carbon dioxide—some frequently asked questions

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Recently there has beenconsiderable interestfrom the media and thepublic about geologicalsequestration of carbondioxide. However thisincrease in publicawareness has alsoshown that someconcepts thatgeoscientists take forgranted are not alwaysfully understood.


What are ‘deep sal ine reservoirs’?Under normal conditions the pore space in rocks close to the surface arefilled with fresh or brackish water. Rocks which contain water that is freshenough to be used for humans or stock are called aquifers. Where the rockis exposed at the surface it is able to be recharged by rainfall. This causes aflow of water through the aquifer.

However, deeper in the geological section below the shallow aquifers,the pores are filled with highly saline waters that have only moved slowly, ifat all, over millions of years. This length of time together with pressure ofdeep burial has resulted in these waters dissolving minerals from the rocksand reaching salinities sometimes many times that of seawater. Rockformations which contain these highly saline waters are called deep salinereservoirs.

These highly saline waters do not rise to the surface and are only foundduring the search for oil and gas in the deep subsurface. They are too deepand too saline for any practical use and it is it is proposed to store thecarbon dioxide in these reservoirs.

How will the carbon dioxide be stored in the rock?Carbon dioxide behaves in the subsurface in the same way as naturallyoccurring oil and gas. Oil and gas are more buoyant than water, and whenthey are generated in the subsurface by the action of the earth’s heat, theyenter the water filled pores of the rock and rise until they encounter apermeability barrier such as a shale bed. If the shape of the barrier is suchthat they cannot escape sideways, the fluids will remain trapped there ashydrocarbon accumulations for millions of years. It is these traps that oilcompanies explore for.

In geosequestration, carbon dioxide will be injected into the rock as asupercritical fluid, which means it is as dense as a fluid but behaves in manyways like a gas. This carbon dioxide will act like the naturally occurringgases and gradually rise from where it is injected until it reaches a barrierthat will stop it from rising further. Careful selection of the injection site willensure that such a barrier exists in the path of the rising carbon dioxide.

Over time, much of the carbon dioxide will dissolve into the groundwater and be held permanently in solution. Some will react with minerals inthe rock and be precipitated out as new minerals leaving only a smallamount to remain trapped as a supercritical fluid.

Could the carbondioxide contaminatethe fresh water supply?The selection of the injection site isone of the most important issues inthe underground storage of carbondioxide. Because the aim of theprocess is long term storage, anyinjection site where there is not anadequate barrier between the deepreservoir and the shallow aquiferwould be unsuitable forgeosequestration.

From studies of oil and gasfields, scientists have a clear ideaof which seals or barriers workbest in each area. Often these sealsare the same ones that already sealsubsurface oil and gasaccumulations

The identification of suitablestorage sites is a critical part of theresearch that Geoscience Australiais currently undertaking for theCO2CRC.

How long wil l i t wil lbe trapped there?The petroleum industry is over ahundred years old and during thistime geologists and other scientistshave been studying the conditionsunder which oil and gas aregenerated and trapped in thesubsurface. The importance of oilto the world economy since themiddle of the twentieth centuryhas meant considerable resourceshave been directed atunderstanding the environment inwhich hydrocarbon accumulationsoccur and how they are preserved.

Research in hydrocarbon-bearing basins worldwide hasshown that it is possible todetermine the time that the sourcerocks started to generate oil andgas, and show how long thesefluids have been held securely inthe adjacent traps. In almost allcases this is tens to hundreds ofmillion years. The fact that thesealing rocks have held naturallygenerated oil and gasaccumulations over such a period,often with naturally occurringcarbon dioxide, demonstrates thatthey can contain carbon dioxidethat is purposefully injected intothem for a very long time.

Figure 2. Under high magnification the pores between the grainsin this sandstone can be seen.

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Where are the best s i tes for long term carbondioxide storage?Previous research carried out by Geoscience Australia has demonstrated thatsedimentary basins, particularly those that are hydrocarbon producing, arethe best geological provinces for the storage of carbon dioxide. This isbecause the conditions that allow for the trapping of oil and gas are alsothose required for the storage of carbon dioxide. These basins are also theones we have the most information about because it was gathered whilstexploring for hydrocarbon resources.

However some basins that lack suitable source rocks for oil and gascould also make excellent storage sites, although less is known about themsince they are less explored.

Gas fields from which almost all the gas has been extracted (depletedfields), are the prime candidates for successful storage. This is because theyhave already demonstrated they can trap and retain large volumes of gas. Inthe USA, fields of this type which are close to populated centres are oftenused to store natural gas produced from more remote locations.

In addition, some other structures that have never contained oil or gascould also provide suitable sites but these will need further research todemonstrate their potential.

Could a hydrocarbon seal leak?Under normal conditions the seal of a hydrocarbon trap may start to leak,and allow small quantities of gas to pass through and continue to moveupwards through the rock column until it is trapped against barriers, orsometimes to be released at the surface as ‘seeps’. This process reduces thepressure on the seal which then ‘closes’ again. In the natural world thisprocess is uncontrolled.

However in a carbon dioxide injection project the capacity of the rockseals will have been measured in the laboratory and their limits known. Inaddition the injection wells and the storage site will be monitored by remotesensing devices that will enable the process to be slowed or halted if thepressure builds up faster than anticipated. This will allow excess pressure tobe dissipated and when conditions are right, injection can re-commence.

This knowledge of the way the natural system works will enable theinjection of the carbon dioxide to be controlled in such a way that it will notthreaten the seal. If the seal is not perfect, there could be some potential forsome gas to slowly leak out over time, and start to travel upwards throughthe overlying rock. However the complexity of the normal geological columnis such that any escape pathway would be tortuous and the fluid movementslow, so that the time taken for even small amounts to reach the surfacewould be of the order of thousands of years.

Do we have the technology to inject carbondioxide underground?The basic technology used to inject carbon dioxide deep underground hasbeen used in the petroleum industry for some time to ‘enhance’ oil or gasrecovery from depleting oil reservoirs. Currently there are severalinternational pilot projects directly involving the injection of carbon dioxideinto rock.• In Saskatchewan, Canada, carbon dioxide is being used for enhanced oil

recovery in the Weyburn Field. • In Poland, carbon dioxide is being used to help extract methane from

coal beds that are too deep to mine. • In the Norwegian North Sea, in the first direct sequestration project,

naturally occurring carbon dioxide is being stripped out of methane fromthe Sleipner Field and being reinjected into a deep saline formation 900metres below the sea bed for storage (figure 3). Since this project startedin 1996 over one million tons of carbon dioxide has been injected peryear, and seismic techniques have monitored the successful dispersionand trapping of the gas within the formation.

• In a similar project in Algeriawhich commenced in 2004,carbon dioxide is stripped fromthe natural gas produced at theIn Salah Field and reinjectedback into the gas reservoir forlong term storage at the rate ofone million tonnes per year.

These examples and a widerange of other enhanced oil andgas recovery projects from placesas diverse as the USA, Turkey,Mexico and the Russian Federationdemonstrate the maturity of thetechnology of carbon dioxideinjection.

Geosequestration is a leadingedge, proven technology that is animportant part of the challenge toallow the benefits of plentifulenergy to be enjoyed by bothdeveloping and developedcountries whilst not continuing toadd to the greenhouse gas load inthe atmosphere.

The work of GeoscienceAustralia in researching andidentifying suitable sites forgeological storage of carbondioxide will ensure Australiacontinues to be a leader in thedevelopment of this technology.

For more information phoneRick Causebrook on +61 2 6249 9366 or [email protected]

Figure 3. The Sleipner Project in theNorwegian North Sea has injected onemillion tonnes of carbon dioxide into asandstone 900 metres below the seabedevery year since 1996.

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Geoscience Australia has recently undertaken aninternal review of its national mapping and remotesensing activities to refine its strategic direction inthe context of current government policies.

A significant influence on the review was the technological revolution thatis sweeping through the spatial data world. This revolution encompasses theapplication of new digital mapping technologies, the integration of globalpositioning systems with digital spatial information and the evolution ofsecond generation web technologies.

These technologies are revolutionising the way governments, companiesand the public think about and use geographic information. WhilstGeoscience Australia distributed 136 740 paper maps during the 2002-03financial year, digital products and distribution through the web constitutesa growing means of data transfer. Web downloads of Geoscience Australia’stopographic information had increased to 6030 per month by October 2004,making a total of 49 422 downloads since January 2004. Increasingly usersare demanding accurate and current data and information that is deliveredfaster with greater reliability and in ways that can be digitally integratedwith their own information in real time—commonly referred to asinteroperability.

In Australia, constitutional responsibility for land surveying andadministration lies with the state and territory governments. Consequentlythe review has focussed on contemporary needs at the national level whilsttaking into account the changing technological environment and theconstitutional arrangements.

National mapping roleThe predecessor organisations to National Mapping Division (NMD)undertook the initial national mapping program at 1: 250 000 and 1:100 000scales in partnership with the state and territory governments and ArmySurvey Corps in response to the needs of national development followingWorld War II. Subsequent work has focussed on maintaining the map serieswhilst other parts of the government infrastructure built to support nationaldevelopment were restructured and privatised. As a result of this and thetechnological revolution, the 1:250 000 scale map series has been fullyrevised and is now available as both paper and digital products.

The new direction explicitly addresses the key policy drivers of theAustralian Government and seeks to capitalise on developments intechnology. The emphasis is on providing national geographic informationfor government purposes and in a form that makes it accessible and useablein a digital environment. The policy drivers originate from GeoscienceAustralia’s parent department (Industry, Tourism and Resources), explicitroles that have been agreed for Geoscience Australia and determiningwhere these responsibilities can be delivered more effectively throughpartnering. The policy drivers are emergency management, defence,marine zone management, Australian Government national mapping needsgenerally, public access and industry development. • Emergency management—Following the Council of Australian

Governments (COAG)agreement on emergencymanagement arrangements in2002 and mapping issuesidentified in the recent,parliamentary inquiry report ‘ANation Charred: Report on theinquiry into bushfires’, NMD isimplementing a project to meetemergency management needsfor geographic information.This entails a pilot 1:100,000scale mapping programcomprising map sheets inpriority areas in the ACT, NewSouth Wales, Queensland,South Australia, Victoria, andWestern Australia to supportstate emergency managementrequirements

* It will also provide geographicinformation to underpin anational natural hazard riskassessment program beingundertaken by GeoscienceAustralia’s Geohazards Division.

• Defence—Under a Service LevelAgreement with the DefenceImagery and GeospatialOrganisation, NMD willcontinue mapping priority areasof Australia to defencespecifications using NMD’scontractor panel. Thispartnership in mappingfacilitates national coverage,improves the use anddevelopment of a consistent setof national topographic dataand contributes to developmentof the spatial informationindustry through the contractorpanel.

New directionsfor National Mapping Division


• Marine zone management—As part of the science program to supportthe Australian Government’s Oceans Policy, NMD is commencingdevelopment of an Australian Marine Spatial Information System (AMSIS)to meet the needs of the National Oceans Office and other AustralianGovernment marine agencies. NMD will also continue to work jointlywith the parent department’s Petroleum and Marine Division as well asthe Departments of Foreign Affairs and Trade and Attorney-General onLaw of the Sea and boundary delineation matters.

• Other government priorities—The 1:250 000 scale national seamlessdatabase of topographic information will be updated so the oldestinformation will be circa 2000 and then continuously updated. This willprovide a current database of fundamental topographic information foraccess at 1:250 000 scale and will underpin the production of smallerscale products and reference maps. This database will be madeavailable free through the web and will also be used to produce a seriesof 1:1 million aeronautical charts with Airservices Australia as well asthematic layers and maps on demand for emerging priorities.

• Public access—The relationship between NMD and its clients will changefrom one based on a ‘Product or Service Offering’ to one based more on‘Needs and Relationships’ with its key clients. NMD will retain a productfocus for meeting the mapping needs of the general public under theSpatial Data Access Policy. Products under the well known brand nameslike NATMAP, GEODATA and ACRES will continue to be made availableto the public as paper, digital and web based products.

• Technology and industry development—The new model will enable NMDto function in smarter ways and to increase our value to key governmentclients whilst meeting the broader needs of the community.Technological innovation will be a key component of the new directionsand NMD is participating in the Spatial Information Cooperative ResearchCentre to both develop and capture technological benefits. The benefitswill include real-time application of remotely sensed data for emergencymanagement and 2D and 3D visualisation of data sets.

The strategic development and application of GIS techniques andprovision of high quality geospatial services across Geoscience Australia willcontinue. At the same time, maintenance of the existing seamless databaseand collection of new data will progressively switch from the ‘map sheet’based system to a theme or layer-based system. AMSIS will be similarlydeveloped as an authoritative source of marine spatial data withinteroperability as a key strategic objective. Increased access to ‘publicgood’ data over the web and increased functionality including, eventually,web services will be a key focus of the new directions.

Consistent with Geoscience Australia’s position as an agency of theIndustry, Tourism and Resources Portfolio, NMD will continue to assistindustry development through contracting out of services, improved accessto information, and technology transfer. NMD’s contributions tointeroperability across government agencies and to the Spatial InformationCRC, and its relationships with contractors, are ways in which GeoscienceAustralia can both achieve innovation in its National Mapping Program anddevelop industry capability. The utilisation of contractors for thedevelopment and delivery of Geoscience Australia products leads totechnology transfer to and from the small business sector which in turnstrengthens industry capacity. This approach aligns with the objectives of theSpatial Information Industry Action Agenda for development of industrycapability, particularly in relation to improved data access and innovationthrough research and development.

National remote sensing role A detailed review of the Australian Centre for Remote Sensing (ACRES) hasbeen undertaken in light of its nationally strategic position in receiving anddistributing remotely sensed data for both scientific and operationalapplications. The review re-affirmed the importance of the national rolecarried out by ACRES and recommended that ACRES become more active indeveloping national approaches to remote sensing.

Although remotely senseddata is used extensively inGeoscience Australia’s mappingprogram and to a lesser extent inother Geoscience Australiaprograms, the principal externaluses include environmentalmonitoring, crop analysis and mapproduction. Most of theseapplications are for Australian,state and territory governments’purposes. A key finding was thecontinuing need for anddependence on access to mediumresolution multi-sensor data suchas that represented by the Landsatseries of satellites, an ongoingneed for access to data fromspecialist sensors and withdifferent levels of resolution. The review found that satellite dataprovision across the world is avery complex mixture of publicsector and private sector activity.Certain types of data and servicesare simply not available from theprivate sector at this time, althoughthis could change with time.Similarly new sensors are beinglaunched regularly by overseasgovernment agencies and thesecreate new opportunities for newremote sensing applications for thenational benefit.

As a result of the review,Geoscience Australia will bestrengthening its role to betterstrategically position ACRES tosupply public-good satellite datainto the future. It will work withits clients and stakeholders tobetter track emerging programneeds and will establish aTechnical Reference Group toassist development of a technicalstrategy to meet ongoing andemerging demands. It will activelyengage with international satelliteoperators to plan access to newsatellites and negotiate access toexisting satellites to mitigate thefailure of a crucial satellite orsensor. A key part of the strategywill be to ensure that ACRES’sactivities complement those of theprivate sector.

For more information phoneTrevor Powell on +61 2 62499050 or [email protected]


Nutrients such as nitrogen, phosphorous, and silica have a significantinfluence on the diversity and abundance of living resources in estuaries andelsewhere. Many interactions occur between organisms such as plants, fish,bacteria, and the nutrients in water and sediments.

Aquatic plants need dissolved nutrients from the water, which oftenlimits their growth. Sea grass and algae, in turn, provide the essential habitatand food for higher organisms such as fish. In addition to nutrients enteringthe estuary from rivers and creeks, nutrients are added to estuarine waterthrough the decay of biomass in the water and in sediments.

The nutrient puzzleNutrients are present in various (chemical) forms and in variouscompartments of a waterway including the water itself, biomass andsediments. Nitrogen(N), for example, is present in the water as dissolvednitrate (NO3

-), ammonia (NH4+), dissolved organic nitrogen (DON), and as di-

nitrogen (N2). Plants make up a major proportion of the overall biomass. The plants

can be free-floating (pelagic) and microscopically small (phytoplankton) orattached to the sediment (benthic). Benthic plants can be large such as seagrass (macrobenthic plants) or they can form a millimetre-thick film ofmicroscopically-small algae (microbenthic algae).

The surface sediment underlying the water attracts most of the deadbiomass and is highly reactive, moving and transferring nutrients to otherestuarine compartments because bacteria causes the biomass to decompose.Below the reactive surface sediment layer, microbial breakdown of organicmatter is much slower and the sediment serves as a storage compartment fornutrients (‘refractive’ sediment).

Figure 1. The estuarine nutrient cycleconsists of various compartments withdifferent characteristic biota. Distinctivereactions involving nutrients take place.

How estuaries cope with nutrientsHow estuaries cope with nutrients▼

Various forms of nitrogenmove freely between the differentcompartments, resulting in acomplex network ofbiogeochemical processes (figure1). These processes involve plantand bacterial activity and aremostly affected by the physical-chemical conditions such as lightand nutrient availability,temperature, and sedimentation.

An estuary can be described asthe transition between the riverand the ocean with freshwater andassociated nutrients entering theestuary and an exchange gatewayat the ocean side. Depending onthe proportion of freshwaterentering and brackish-marine waterexiting, estuaries have highlyvariable water residence times.Under high river water runoffconditions, the estuary is flushed,while the residence time in thesame estuary can be very longunder low runoff conditions orwhen the water exchange with theocean is restricted. Nutrients areefficiently trapped and recycledwithin the various estuarinecompartments when the waterresidence time is long, whereasflushing leads to significant nutrientoutflow to the ocean.

Poor and deteriorating coastalwater quality is associated withincreased levels of dissolvednutrients (NO3

- and NH4+) and

excessive plant growth, a trend inwater quality referred to aseutrophication. Balancing the inputand output of estuarine nutrients,such as nitrogen, allows scientiststo estimate a sustainable nutrientload. While river runoff is theprimary nutrient input, the outputcomprises the nutrient outflow tothe ocean, the burial of nutrients insediments, and the production ofN2 in sediments. N2 is inert andeventually escapes to theatmosphere. The processproducing N2 is calleddenitrification and has the capacityto typically remove 50 to 90 percent of all nitrogen entering theestuarine nutrient cycle.

Estuaries vary in shape and size, they support andsustain different ecosystems and are exposed to everchanging levels of nutrients from the catchment.Scientists can assess and predict the possibility ofestuarine vulnerability to eutrophication by analysingthe nutrient processing in sediments and in the water.


Eutrophication This term refers to an increase inbiomass production within anecosystem over time. In order tocompare the degree ofeutrophication between differentaquatic systems, a classification for(plant) biomass production wasestablished ranging fromoligotrophic (< 100 g C m-2 y-1) tohypertrophic (> 500 g C m-2 y-1)conditions.1

A common misconception is tothink that high biomass productionmeans that living resources withinour coastal waterways are in abetter condition. The implicationsof a high biomass production aredramatic for the health of anaquatic ecosystem and include theloss of habitat such as sea grassmeadows, a decrease inbiodiversity, and mass mortalityinduced by anoxic water or therelease of toxins from certaingroups of phytoplankton.

During eutrophication acascade of physical—chemicaleffects lead to impacts on life in thewater column and within thesediments (figure 2). As long as anestuary receives little nutrient loadsfrom the catchment, slow-growingmacro plants, (particularly seagrass) thrive, and provide shelterand support for a highly diverserange of life forms including youngfish. Once nutrient loads increase,the fast-growing phytoplanktonincreases, reducing the lightavailable for benthic plants. As aconsequence, sea grass abundancedeclines and often fast-growingmacro algae start dominatingbenthic plant communities. Plantgrowth will now become sporadicand follow pulses of nutrient-richrunoff. The sudden availability ofnutrients together with the reducedsalinity conditions promote newphytoplankton assemblages, whichmay contain a toxin-releasingspecies.

The phytoplankton bloomphase is then followed byenhanced oxygen consumption atthe sediment surface where bacteriadecompose organic matter. Thisenhanced oxygen demand oftenleads to anoxic bottom waterconditions, particularly when theestuary is poorly flushed.Consequently, mass mortalitybecomes inevitable for benthic lifeunder anoxic conditions.

Case studies: St . Georges Basin (NSW), WilsonInlet (WA), Fitzroy River Estuary (Qld)St. Georges Basin and Wilson Inlet are very similar in size and shape, bothare wave-dominated estuaries with a large surface area of 42 and 48 km2,respectively. However, St. Georges Basin is significantly deeper and hastherefore twice the water volume of Wilson Inlet. Secondly, the two estuariesare located in different rainfall zones and receive different volumes of waterfrom the catchment. St. Georges Basin receives a fairly continuous riverrunoff which relates to a uniform rainfall throughout the year, while WilsonInlet receives a few major pulses of river water, typically between Augustand December. These freshwater pulses add up to twice the total volumethat St. Georges Basin receives during a year. Thirdly, the ocean gateway, orbarrage, of Wilson Inlet is only open when the estuary receives major riverrunoff and about two months thereafter (August to February), while St.Georges Basin has a year round water exchange with the ocean.

These three physical differences in the estuarine environment havemajor implications for differences in the nutrient cycling, the biota, and thesusceptibility to effects of eutrophication: The temporarily open barrage ofWilson Inlet leads to the accumulation of highly saline (marine) water at thebottom of the estuary, while the large volume of freshwater entering theestuary forms a layer on top. The estuary becomes stratified. Thisstratification restricts the vertical water exchange and oxygen re-supply tothe estuary bed, where oxygen is rapidly consumed. Consequently, thebottom water becomes anoxic. At the same time, the surface water becomesenriched with nutrients such as nitrate, which then stimulates phytoplanktongrowth and leads to a major bloom(www.wrc.wa.gov.au/public/community/Wilson_Inlet_No5.pdf). On anannual basis, however, most of the dissolved nutrients are taken up bybenthic plants including sea grass and benthic micro phytoplankton. Thelatter is only possible because large areas of Wilson Inlet are shallower than3 metres and can receive light deep down on the estuary bed, a criticalcondition for benthic plant growth.

In contrast, St. Georges Basin is distinctively deep, which does not allowbenthic plant growth in large areas (figure 3). This conclusion is numericallysupported by the Simple Estuarine Response Model (SERM,www.per.marine.csiro.au/serm2), which predicts Wilson Inlet and St.

Figure 2. Increased nutrient loads from the catchments lead to an increase in thedegree of eutrophication. A cascade of physical-chemical and biological effects leadto deteriorating water quality.

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Georges Basin to have about thesame rate of total plant growth(primary productivity), butdistinctively different proportionsin pelagic and benthic productivity.Benthic plant growth in WilsonInlet is about 90 per cent, whereasit is only 10 per cent of the totalprimary productivity in St. GeorgesBasin. As a consequence, ongoingeutrophication in St. Georges Basinhas probably increasedphytoplankton growth and therebyreduced light penetration to thebottom. This is a typical effect ofeutrophication and is likely to havecontributed to the sea grass declinein St. Georges Basin, over the last40 years.2

Similar to Wilson Inlet, thehydrology and nutrient cycling ofthe tide-dominated estuary of theFitzroy River is strongly dependenton the season. Here, rainfall ispredominant during the summer,and major floods occur usuallybetween December to March. TheFitzroy River Estuary is alsoaffected by the large tidal range of4 metres. Water and its suspendedmatter moves rapidly back andforth in tidal creeks, and extensive(intertidal) areas are temporarilyimmersed during the tidal cycle.The intertidal areas in tropicalnorth Australia consistpredominantly of mangroveswamps and, to a lesser degree,intertidal mud flats. Mangroveswamps are highly productive andtherefore constitute a major coastalecosystem. Vegetated intertidalareas remove large amounts ofcarbon 3 and associated nutrients.In addition to the high nutrientburial, denitrification is highlyefficient in mangrove sediments, sothat these intertidal areas serve asa valuable filter for catchmentderived nutrients. It has beenshown that seagrass is effectivelyprotected by fringing intertidalwetlands against excessivecatchment N loads.4 In the case ofthe Fitzroy River Estuary, theaverage width of a mangrove beltbordering both sides of the estuarychannel is 1 km (figure 4). Here,nutrient levels in the estuary, plantproductivity and nutrient flux arecontrolled predominantly by thecombination of the biogeochemicalfunctions of the mangrove swampsand their aerial extent, as well asthe connection of these areas byintertidal creeks and the tidalflushing.

References:1. Nixon SW. 1995. Coastal marine eutrophication: A definition, social

causes and future concerns. Ophelia 41:199—219.2. Meehan A. 2001. Conservation status of the seagrass Posidonia australis

in south east Australia. PhD thesis, Univ. Wollongong, 230 pp.3. Chmura GL SC Anisfeld DR Cahoon JC Lynch. 2003. Global carbon

sequestration in tidal, saline wetland soils. Global Biogeochem. Cycles17, 1111.

4. Valiela I & Cole ML. 2002. Comparative evidence that salt marshes andmangroves may protect seagrass meadows from land-derived nitrogenloads. Ecosystems 5:92—102.

For more information phone Ralf Haese on +61 2 6249 9100 or e-mail [email protected]

Figure 4. Water flow and nutrient reactions of the Fitzroy Estuary (Queensland) arestrongly influenced by the high river water discharge during the summer and the largetidal range. Intertidal areas such mangrove swamps border the river channel and tidalcreeks and serve as zones of significant nutrient processing.

Figure 3. Large areas of St. Georges Basin (New South Wales) are too deep to allowlight penetration to the estuarine bed. Consequently, benthic plants such as sea grassare restricted to a relatively small area, so that primary productivity in surface water ispre-dominant. Seagrass distribution according to Meehan.2

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Fitzroy Estuary andKeppel Bay Project

Water column surveyIn August this year, a team ofscientists from Geoscience Australiaand CSIRO Land and Waterundertook a dry-season survey ofthe water column and bottomsediment properties in Queensland’sFitzroy Estuary and Keppel Bay.

They gathered in situ data, inparticular time series measurementsof water velocities and turbidity,together with physical and intrinsicoptical properties of the watercolumn and sampling of suspendedsediment.

These data will: • help parameterise and validate

the mathematical models ofhydrodynamics and sedimenttransport currently underdevelopment;

• facilitate the use of satellitemeasurements of surface waterchlorophyll and suspendedsediment concentrations toprovide synoptic data for all ofKeppel Bay; and

• allow further exploration of thetemporal dynamics of sedimentre-suspension and its impact onshort term nutrient availabilityin Keppel Bay.

Vibrocoring in Keppel BayScientists began work on a vibracoring project in Keppel Bay and theFitzroy River estuary in September.

They aimed to obtain sediment cores, to a maximum depth of threemetres below the seabed, at pre-selected sites within the study area in orderto:• ‘ground-truth’ the sub-bottom profiles for Keppel Bay and assist in the

interpretation of the sedimentary sequences identified in these acousticdata; and

• obtain sediment samples of the various Holocene and Pleistocenesubsurface units for analysis and characterisation.

Over a two day period, a total of 25 cores (19 aluminium and six PVCcores) were recovered from the 20 pre-determined sites (figure 1). One coreat each site will be cut longitudinally and split to expose the core sample.The core will then be photographed and logged prior to sampling.

Logging includes visual estimates of colour, texture and composition ofthe various lithologic units, noting any major stratigraphic changes. Samplesof the various units are collected from one of the core halves. The other halfis run through a GeoTek logger to identify physical changes in the sedimentand then archived for future reference.

The composition and texture of sediment samples from the vibrocoreswill be examined using various labratory intsruments such as XRD, XRF/ICP-MS and laser grainsize methods.

Examining these vibracores will allow deposits to be correlated andbuild a stratigraphic framework for Keppel Bay. Along with the sub-bottomprofiles, these data will be used to reconstruct the Holocene and recentevolution of Keppel Bay. It will also help to quantify the volume ofsediment in the bay derived from the Fitzroy River.

Additional cores at selected sites were collected to assess iron speciationwithin the sediments. Biomarker analysis will be completed by projectpartners, CSIRO Marine in Hobart (Dr Rhys Leeming) and CentralQueensland University (Dr Viky Vicente-Beckett) who will measurepesticides within the estuary sediments.

Acoustic mapping of the estuary and seabedThe Fitzroy Estuary is one of a number of tropical macrotidal estuaries innorthern Australia. In this part of Australia there is an urgent need to assessthe potential impacts of catchment land use on the estuarine system andcoastal zone, including the Great Barrier Reef Marine Park.

The Coastal CRC Coastal Water Habitat Mapping project is assessingthese impacts using sonar systems such as the multibeam Reson Seabat 8125and Klein 5000 sidescan sonar.

Using these systems, scientists have acoustically mapped the bed of theFitzroy Estuary, and sites in the adjacent Keppel Bay.

An added bonus of this project is the testing of the sonar equipment inhighly turbid and muddy water, with tidal ranges of up to five metres.Adverse environmental conditions such as strong currents, zero watervisibility and notorious sandbanks combine to make sonar surveystechnically challenging. To date, these have been the most difficultenvironmental conditions in which the CRC has used this equipment.

The Reson 8125 used to capture a very high resolution bathymetricdataset in Keppel Bay, focused on a range of sediment bedforms. A repeatsurvey of these bedforms is being used to assess rates of movement, andquantities of sediment transported from the river to its final destination inKeppel Bay.

The Klein 5000 sidescan sonar has produced imagery of varioussediment bedforms in the main estuarine reach of the Fitzroy River (figure2). It shows the erosion of sediments from the river bank with largesandwave or ‘slugs’ moving down the river during flood periods only, andoverlain by smaller bedforms which move during each tidal cycle.

COASTAL CRC project update

Figure 1.Scientists recovera submersiblevibrocorer fromthe sea bed inKeppel Bay


Central Queensland’s FitzroyRiver and Keppel Bay, areexamples of typical macro-tidalestuaries and inner shelfenvironments found in tropicalnorthern Australia.

About the size of England, theFitzroy River has one of the largestriver catchments in Australia, atapproximately 14 million hectares.

The Fitzroy is atypical of mostAustralian rivers because it has veryhigh sediment yields. Further studyof the acoustic data and sedimentsamples, including cores, grabs,and water column information,help to determine how catchmentland-use practices affect the riverand coast.

This collaborative fieldoperation included scientists andtechnicians from Curtin University(WA), Defence Science andTechnology Organisation (DSTO),and Geoscience Australia.

Habitat maps of near-prist ine estuaries GIS maps of sedimentary habitats in73 near-pristine estuaries inQueensland are now complete andavailable for download atwww.ozestuaries.org. 'Near-pristine'estuaries are those with relativelylittle or no apparent human impacts(figure 3). Queensland has thegreatest estuarine diversity as wellas the largest number of estuariesin any state (305). It also has thehighest number of 'near-pristine'estuaries (182).

Scientists plan to map 163 near-pristine estuaries from aroundAustralia. The new maps will allowcomparisons between regions andestuary types without the overprintof impacts related to post-Europeansettlement.

They will also providebaselines from which to gaugechanges that have occurred inestuaries in the more populatedparts of Australia. These maps willalso fill a gap in currentknowledge, as predominantlymodified estuaries were mapped aspart of the National Land and WaterResources Audit. Using newmethods, the latest maps are moreaccurate, detailed, and visuallypleasing than the Audit maps.

Further development of OzEstuaries databaseOzEstuaries is entering a new phase of development. The web interface isundergoing a restructure, which will enable easier navigation and providemore functionality, including enhanced data query capabilities.

A significant amount of new coastal geoscientific data is being added, aswell as images, data reports, additional online GIS layers, bathymetry dataand 3D visualisations.

These data and information are derived from a range of current CoastalCRC projects, including the Coastal Water Habitat Mapping and FitzroyEstuary projects. Upgrades will start coming online in the next few months.

For further information phone Brendan Brooke on +61 2 6249 9434 ore-mail [email protected]

Figure 3. Sedimentary habitat map forKennedy Inlet (left) and Escape River(right), located near the tip of CapeYork, Queensland.

Figure 2. A sidescan sonar image of the bed of the Fitzroy Estuary main channel,collected using DSTO’s Klein 5000 system.

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Shifting sands

I n B r i e f


A clearer picture of the shifting sands and disappearing seagrass in TorresStrait is beginning to emerge. A second marine survey by GeoscienceAustralia scientists in October has revealed that seasonal winds are theprincipal cause of widespread sandwave movement in Torres Strait.

The survey was the second this year aboard James Cook University’sresearch vessel James Kirby investigating the movement of sandwaves nextto Turnagain Island. Two study sites, southwest and southeast of the island,were resurveyed with multi-beam swath sonar. The first survey completed inApril fortuitously captured the moment when the sandwaves reversed theirorientation from east to west, associated with the end of the monsoon andstart of the trade-wind season (see AusGeo News 75). The second sonarsurvey completed in October showed that the crests of the sandwaves hadmoved up to several hundred metres further to the west over that time(figure 1).

Detailed measurements of wave and tide currents were also collected bysix oceanographic moorings deployed in the vicinity of the sandwaves forthe 21-day survey to provide insights into the main oceanographic processescausing sediment transport. While local waves and tides are responsible forresuspending the sand grains on the seabed, it appears that it is the longer-term net water movements driven by the prevailing winds that are

responsible for the formation andmigration of the sandwaves.

The surveys have revealed forthe first time, and inunprecedented detail, a picture ofthe dynamic nature of the seabedin Torres Strait. Further analysis ofthe sonar and sediment data fromshallow cores collected from thesandwaves will be undertaken overthe next few months to determinethe amount of sand that has movedover the seabed during the 2004trade wind season. This will bedetermined by calculatingdifferences in the position of thecrests of the sandwaves andestimates of the volume of sand.Comparison of the sonar data fromthe April and October surveys willbe conducted to determine theextent of adjustments in seabedelevation. This can be translatedinto changes in the distribution ofsand contained in the sandwavesover time.

The principal aim of thesurveys is to increase ourunderstanding of the processescausing the sandwaves to move,and their potential effects on thedistribution, abundance andsurvival of seagrasses in TorresStrait. Because the sandwaves areextremely mobile, they have thecapability to rapidly cover seagrass,which grows next to thesandwaves. Widespread smotheringof seagrass beds will haveconsequences for dugong andgreen turtle populations which eatthe seagrass. Traditional hunting ofthese creatures by the local TorresStrait Islanders will be affected.

The surveys are part of a largerprogram managed by the ReefCooperative Research Centre(Torres Strait Program) investigatingseabed ecosystems, and modellingof physical and biologicalprocesses occurring in Torres Strait.Results from Geoscience Australia’ssurveys will contribute directly tothe development of managementplans for the region.

For more information phoneAndrew Heap on +61 2 6249 9790 or [email protected] Figure 1. Swath sonar images showing the morphology of the sandwaves south-

east of Turnagain Island in April (top) and October (bottom) 2004. Note that thesandwaves have changed from east to west under the influence of the trade winds.

▼Shifting sands UPDATE


I n B r i e f

Recent surveys indicate that global exploration is re-bounding strongly fromthe major downturn of the last five years on the back of high gold prices andlarge increases in base metal prices driven by strong demand from China'sindustrialisation and urbanisation. Australian mineral exploration activity hasalso increased but its share of global exploration budgets continues todecline.

Austral ian mineral exploration improvesAustralian mineral exploration expenditure for the 2003-04 financial year,reported by the Australian Bureau of Statistics, was $786.7 million, anincrease of 7.4% over 2002-03 figures (figure 1). Exploration increased in alljurisdictions except New South Wales and the Northern Territory. WesternAustralia dominated exploration expenditure with 59% of total spendingfollowed by Queensland with 16%. Gold dominated exploration spendingwith 51% of total exploration, followed by base metals (19%), coal (10%) andiron ore (8%). Exploration spending was up for most commodities, exceptfor mineral sands and diamonds, which each fell by approximately 13%(figure 1). The largest percentage increases in exploration expenditure werefor uranium and iron ore.

Global mineralexploration up stronglyThe recently released 2004 MetalsEconomics Group survey of globalnon-ferrous metal explorationbudgets reports significant increasesin global exploration budgets for the2004 calendar year, an increase ofmore than 50% on the previous yearto ~$US3.7 billion (figure 2).Exploration budgets were upsubstantially on last year’s figures inall regions surveyed. Countriesshowing the largest increases wereMongolia (exploration at the OyuTolgoi copper-gold deposit) and theUSA (increased gold exploration inthe Carlin district).

Australian budgets alsoincreased significantly in the 2004survey but its share of global non-ferrous mineral exploration budgetsfell to 14.7%, after Latin America(21.8%), Canada (19.6%), Africa(16.1%), and the rest of the world(15.4%). This was the first timeAustralia has not been in the topfour regions for mineral explorationand its lowest recorded share ofglobal mineral exploration (figure 2).(continued on page 24)

Australia’s mineral exploration rankingcontinues to slip

Figure 2. Global non-ferrous metalexploration budgets for 2004 togetherwith Australian non-ferrous metalexploration budgets and Australia’sshare of global mineral explorationbudgets for period 1991-2004. Source:Metals Economics Group CorporateExploration Strategies 2004.

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Figure 1. Australian mineralexploration expenditure 1970-2004 inconstant 2003-04 dollars, based onAustralian Bureau of Statistics datadeflated by Consumer Price Index.

I n B r i e f


In 2003, Geoscience Australia, in partnership with Primary Industry andResources South Australia (PIRSA), conducted a deep crustal seismic surveyacross the eastern margin of the Gawler Craton to determine the crustalstructure in the region of the giant Olympic Dam copper-gold-uraniumdeposit. Scientists recorded and processed over 250 line-kilometres of deepseismic reflection data from two lines centred on the Olympic Dam minesite.

The results provide new insights into the crustal architecture and the firstregional-scale 3D image of this major mineral system.

The Olympic Cu-Au-U province is host to the world’s most outstandingexample of an iron oxide-copper-gold deposit, Olympic Dam. However, thedeposit and the entire eastern third of the Gawler Craton are covered bysedimentary sequences hundreds to thousands of metres thick.

Before the seismic survey, the nature of the crystalline basement and itsminerals systems could only be inferred from potential-field data andobservations from relatively few drill holes.

Initial interpretations show that the Archaean–Proterozoic basement istypical of a fold-thrust belt. It displays thrusts and back-thrusts, related toknown periods of orogenesis, in a comparatively layered crust withPalaeoproterozoic units to depths of 14 km overlying a mid-crustal reflectivelayer.

This layer, about five kilometres thick, displays ramp-flat geometries incontrast to the thrusts above it. Both the velocities and the style ofdeformation suggest it is possibly more mafic than the overlying units. Thislayer is older than the 2.0-1.85 Ga Hutchison Group, perhaps earliestPalaeoproterozoic to late Archaean.

Below the mid-crustal layer, a north-dipping transcrustal shear zoneextends from the southern end of the profile to the Moho, possibly into themantle. It does not appear to be a significant crustal boundary, despite itsprominence. The deep crust of the northern part of the section, however,shows a different seismic character, which suggests that it may be a separateterrane.

The granite pluton hosting theworld class Olympic Dam Cu-Au-Udeposit is clearly imaged. Aboutfive kilometres thick, it is the onlyintrusive body associated withmineralisation apparent in thesections.

The cover rocks are up to sixkilometres thick and show thestructure of their basins and theinfluence of Cambrian inversion.

Interpretations of the GawlerCraton seismic sections are beingincorporated into geophysical,geochemical, and geological modelsof the Olympic Cu-Au-U provinceso that a clear picture of itsarchitecture and tectonic history canbe developed.

In particular, the majorbasement geological units andstructures identified in the seismicdata will be integrated withpotential-field data to develop a 3Dgeological model. This will allowscientists to assess the potential formore mineral deposits in theregion, but also help them tounderstand how this provincerelates to other Archaean andProterozoic terranes within theAustralian continent.

GAWLER seismic study

The Metals Economics Groupsurvey figures are dominated bysurging precious metals explorationwith global gold explorationbudgets up 68% in response tostrong gold prices. The increase ingold exploration budgets (50% oftotal non-ferrous explorationbudgets) in 2004 was accompaniedby a small decrease in diamondexploration (13%); base metalsexploration remained at 26% oftotal spending. Canada,particularly, showed a markedincrease in gold explorationbudgets with its share of globalgold exploration more than treblingsince 1997.

Favourable outlookMineral exploration in Australia is recovering, but at a slower rate than insome other parts of the world. The increase in global mineral exploration isunderpinned by high gold prices and strong demand from China for basemetals and bulk mineral commodities such as iron ore, aluminium and coal.This trend seems likely to continue in the short term. Demand for basemetals and the bulk commodities in the medium term will primarily dependon the rate and extent of economic growth in China and the impact ofcurrent high oil prices on the global economy.

For more information phone Lynton Jaques on +61 2 6249 9745 or e-mail [email protected]

Seamless


I n B r i e f

For almost 50 years Geoscience Australia and its predecessororganisations have mapped Australia at scales from 1:100 000 to 1:20million. For many years manual methods of cartography were used toproduce paper maps, but in the last 15 years, since the introduction ofdigital cartography, a broader range of products, many now in digitalformat, have been produced.

Recent advances in database technology for managing geographicinformation systems (GIS) spatial data have been embraced by NationalMapping Division (NMD) and promise to further revolutionise the wayNMD fulfils its national mapping obligations. In embracing thistechnology, Geoscience Australia has created a seamless topographicdatabase at 1:250 000 scale for the entire continent.

Geoscience Australia approached the technology by initiallydeveloping a functional specification that established the input andoutput requirements of the database. Among the issues considered were:what type of information do we want to store; what do we want to beable to do with the data in terms of maintenance, manipulation andoutput; and, what tools would be required to do these things?

After these and other issues were considered, various options weretested. Hardware and software were bench-marked and the performanceof spatial data formats, such as Oracle Spatial, and SDE binary,compared. A method for populating and validating the database wasformulated and a data model that adhered to national and internationalstandards, maintained historic data, and allowed for future expansioninto other themes and scales was constructed.

The data was modelled using point, line, polygon and multi-polygonspatial entity types and then categorised according to theme, class,subtype, and spatial entity type. Thematically-related and sometimestopologically-related features were grouped. The data model wasdocumented, constructed in Unified Modelling Language (UML), and apilot and a prototype database was developed.

Ten gigabytes of vector data, held in ARC/INFO coverages, was thenreformatted and translated into the new data model. All 513 tiles of datawere edge-matched and their ’bleed-edges’, or overlaps, assimilated. Theresulting database is seamless, continent wide, and arguably moresignificant than any other spatial dataset in Australia. It includes roads,streams, contours and all the other hydrographic, infrastructure,administration, vegetation and relief features appearing on the 1:250,000scale topographic national map series. It is also fully attributed, down tofeature level metadata.

Web pages and programs for delivering the data, and user-customised maps generated from the data, are currently beingdeveloped. Maintenance and validation of the database has commenced.

The seamless database has proved to be faster, more easily managedand maintained, and richer and more intelligent than the sourcecoverages from which it was created. It better retains history andmaintains data integrity.

Seamless topographic data at other scales are now being added tothe database environment. It is envisaged that in the future a full rangeof both standard and on-demand paper and digital products will bederived directly from a single multi-scaled topographic database.

Creation of the seamless database has been a difficult, rewardingand significant step in building the Australian spatial datainfrastructure.

SEAMLESSTOPOGRAPHICDATABASE

becoming a reality

Events CALENDAR 2005

North American Prospects Exhibition

American Association of ProfessionalLandmen26 & 27 January Houston, Texas, USAContact: AAPL, 4100 Fossil CreekBoulevard, Fort Worth, Texas 76137 USAphone +1 817 847 7700fax +1 817 847 7704e-mail [email protected]

PDAC International Convention & Trade ShowProspectors and Developers Associationof Canada6 to 9 MarchMetro Toronto Convention Centre,Toronto, CanadaContact: Prospectors and DevelopersAssociation of Canada, 34 King StreetEast Suite 900, Toronto, Ontario M5C2X8phone +1 416 362 1969fax +1 416 362 0101 e-mail [email protected]

APPEA Conference and Exhibition Australian Petroleum Production andExploration Association 10 to 13 April Perth Convention and Exhibition Centre Contact: Julie Hood, APPEA Limited,GPO Box 2201, Canberra ACT 2601Phone +61 2 6267 0907fax: +61 2 6247 0548e-mail: [email protected]

AAPG Annual Meeting American Association of PetroleumGeologists Annual Meeting andExhibition19 to 22 JuneCalgary, CanadaContact: AAPG Convention Department,PO Box 979, Tulsa Oklahoma 74101-0979 USAphone +1 918 560 2696fax +1 918 560 2684e-mail: [email protected]

AMSA 2005 Australian Marine Sciences Association11 to 13 JulyCrowne Plaza, DarwinContact: PO Box 902, Toowong Qld4066e-mail: [email protected]


Disasters such as the bushfires insouth eastern Australia in 2003highlight the importance of up-to-date and appropriate spatialinformation in responding to andmanaging emergencies. This typeof information is extremelyvaluable as it is used by emergencymanagers to prepare, plan, respondand recover from such disasters. Toensure the information can be usedeffectively, maps need to becurrent, relevant and accurate.

During the 2003 bushfire crisis,Geoscience Australia provided 3 400 topographic maps at 1:100 000 scale to support the firefighting effort, despite almost two-thirds of the maps being more thantwenty years old.

The currency of GeoscienceAustralia’s 1:100 000 scaletopographic map series rangesfrom 1961 to 1990, although arevision of 70 of the maps wascompleted in 2001. There are about3 000 maps in the series andapproximately half are available aspublished maps. However most ofthe data used to create the mapsacross the series are not availablein a modern database environment.

I n B r i e f

In response to emergency management needs and the currency of the1:100 000 scale topographic map series, Geoscience Australia is undertakinga 1:100 000 scale topographic mapping pilot project in several locationsacross Australia. The project is being undertaken in collaboration with Stateemergency management and mapping agencies and is piloting the use of thelatest technology in satellite imagery and Geographic Information Systems(GIS), in generating 1:100 000 data and maps. The tangible outputs willinclude tailored GIS databases and digital and hardcopy maps for thefollowing areas: Karijini National Park in Western Australia, the Gold Coasthinterland in Queensland, Barrington Tops in New South Wales, and the areaaround Benalla in Victoria.

In addition to providing key data and maps in the pilot areas, animportant part of this project is to enhance Geoscience Australia’srelationships with State emergency management and mapping agencies.Geoscience Australia is working closely with these agencies to developtailored specifications for on-going mapping and to establish processes andarrangements that will maximise outcomes and production efficencies.

The spatial databases resulting from this project will be capable ofsupporting the ongoing development and maintenance of topographicinformation at a range of scales, particularly 1:100 000 scale. This not onlybenefits emergency management, but other key national requirements suchas border protection, homeland security and natural resource management.

100K scale mapping pilot to help emergency management

Geoscience Australia and the Australian Greenhouse Office (AGO) haveagreed to cooperate closely on the supply, use and distribution of satelliteimagery used to monitor changes in vegetation. Geoscience Australia’sremote sensing unit, ACRES, has been downlinking Landsat imagery since1979 and has built up an extensive national imagery archive. The AGO hasused this imagery as one of the key information sources to construct theNational Carbon Accounting System, used to track Australia’s greenhouse gas emissions.

The satellite imagery shows that between our bicentenary in 1988 and2001, 3.4 million hectares of forested land was cleared across Australia.However, more positively, the amount of carbon dioxide released due toland clearing has reduced between 1990 and 1999. Importantly, Landsatimagery is still being used today for many applications includingenvironmental monitoring, crop analysis and map production. This richdigital information technology helps communities make informed decisionsabout where local and regional action will be most effective. As part of theagreement, ACRES will distribute the AGO image products including 12

epochs of processed imagery from1972 to 2002. The products includea DVD containing three bandcompressed imagery in ECWformat suitable for viewing by non-remote sensing users, as well asfull resolution multi-spectralimagery mosaiced into 1:1 millionmap sheet tiles for use by spatialindustry professionals. ACRES willbe supplying 2004 Landsat imageryto enable the AGO to continuetheir monitoring work into thefuture.

Howard Bamsey, Chief Executive of AGOand Geoscience Australia’s CEO, NeilWilliams signing the agreement.

Agreement signed betweenAustralian Greenhouse Officeand Geoscience Australia


P r o d u c t N e w s

Approximately 123 000 linekilometres of airborne geophysicaldata in the northern Yilgarn Blockof Western Australia has recentlybeen released. The area coveredincludes the entire Cue andKirkalocka 1:250 000 sheet areaand the 1:100 000 sheet areas ofYalgoo and Badja on the Yalgoo1:250 000 sheet area.

The data shows a highpotential for gold mineralisationbut, as a result of the limitedoutcrop, mineral exploration hasbeen hindered. It is expected that

these new geophysical datasets will be a significant asset in mapping theregion’s Archaean geology as well as targeting exploration areas.

This dataset comprises magnetic, radiometric and elevation data fromtwo surveys flown for the Commonwealth Government between April andAugust 2004. The data has been merged with two existing private companysurveys, to provide continuous coverage over the northern Yilgarn region.As a result the magnetic, radiometric and elevation datasets have a variableline spacing of 200 to 400 metres, gridded using an 80-metre cell size.

These digital data (point-located and gridded) are available for freedownload from the web or on CD-ROM for $99 (includes GST) plus postageand handling.

For more information about this dataset visit www.ga.gov.au/gadds.To order the CDs phone Freecall 1800 800 173 (in Australia) or +61 26249 9966, or e-mail [email protected]

Geophysical data released for key areas in WA

ASTER data available soonGeoscience Australia’s remote sensing unit (ACRES) recently signed anagreement with the Japanese Earth Remote Sensing Data Analysis Centre(ERSDAC) to distribute data from the ASTER sensor on board the TERRAsatellite. ASTER is the Advanced Spaceborne Thermal Emission andReflection Radiometer designed to obtain detailed maps of land surfacetemperature, emissivity, reflectance and elevation.

The ASTER sensor consists of three different subsystems—Visible andNear Infrared (VNIR), Shortwave Infrared (SWIR), and Thermal Infrared(TIR). Altogether, 14 discrete spectral bands are covered (see table1). Band3 data from the VNIR system also has an additional backward lookingtelescope for the collection of stereo pairs.

The ASTER products will provide a useful addition to the ACRESproduct range, especially for applications involving geological studies orgeneration of digital elevation models.

Table 1. Characteristics of the three sensor systems of the ASTER instrument

VNIR SWIR TIRBands 1–3 4–9 10–14Spatial resolution 15m 30m 90mSwath width 60km 60km 60kmCross track pointing ± 318km ± 116km ± 116kmQuantisation (bits) 8 8 12

Figure 1. This ‘decorrelation’ imagerepresents spectral variability in the shortwave infrared region of theelectromagnetic spectrum (EMS) capturedby ASTER over the Century Copper / Zincmine in Western Queensland.

Customers will soon be able topurchase archived Australian ASTERdata and to place requests toERSDAC for future acquisitions.

For more information phone Jim Mollison on +61 2 6249 9221 or [email protected]

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The new edition of the Magnetic Anomaly Map and Grid of Australia wasproduced from 19 million line kilometres of survey data from nearly 700surveys. The new generation Magnetic Anomaly Grid Database (MAGDA) isthe cornerstone of a completely new method of matching individual surveygrids.

Developed using the concept of a database with matched Total MagneticIntensity (TMI) grids, it is unlike previous editions, as it allows the extractionof composite grids of any resolution. Included in the release are hardcopymaps at 1:5 and 1:25 million scales, and composite grids with cell sizes of7.2 and 15 seconds of arc (approximately 250 m and 400 m).

This edition was produced using a new compilation of TMI grid data, anew method that matches individual survey grids, and uses independent datato constrain long wavelengths. The resolution of each grid is optimal for thespecifications of the source survey line data. Nearly 700 individual grids havebeen matched and merged into the composite grids, and used to produceimages for the maps (figure 1).

Since the release of the third edition in 1999, new survey data has beenacquired mainly by the state and territory Geological Surveys, and has beenadded to the database. It is estimated that around 19 000 000 line-kilometresof survey data were acquired to produce the grid data, over 10 000 000 line-kilometres more than for the previous edition. The index map (figure 2)shows the distribution of original survey line spacings from which the gridsare derived.

Matching the grids in the database was undertaken using a programcalled Gridmerge, originally developed at Geoscience Australia and nowcommercialised. It uses the statistics of the overlapping regions betweenadjacent surveys to globally minimise the differences in the base levels of allsurveys. Provision has also been made to allow users to remove higher-ordersurfaces from grids. To constrain long wavelengths, an independent data set,the Australia Wide Array of Geomagnetic Stations (AWAGS) airbornemagnetic data, was used to control the base levels of those survey gridswhich overlapped the AWAGS data. Using a convolution operator, the short-wavelength differences between the grids were smoothed.

The TMI image used for thefourth edition map is an example ofa range of products that can beeasily generated from the newdatabase. For example, theindividual grids can convert to anydesired map datum/projection andany selected areas of interestmerged to the desired gridresolution. Databases of derivativegrids can be automaticallygenerated, such as reduced to thepole, vertical derivative andhorizontal derivative products.Preliminary reduced to-the-pole andderivative grids of composites ofthe whole database have also beengenerated, using a tiling procedure.

Products derived from themagnetic database also provideinsights into the distribution ofmagnetically susceptible mineralswithin the Earth's crust. They are ofgreat value to mineral explorationcompanies and researchers of thesolid earth. Magnetic minerals insmall amounts are widespread inthe crust, and become concentratedin zones which highlight thestructures of the crust. This isparticularly important for areaswhich have a significant thicknessof surficial cover (regolith), whichcan mask the underlying crystallinebasement rocks. The magneticsignatures of the basement, aremeasured through the cover andprovide important interpretation todetermine the nature and depth ofthe basement—significantinformation for mineralexploration.

Figure 1. The 1:25 million scale version of the fourth edition of the Magnetic AnomalyMap of Australia.

Figure 2. The distribution ofsurvey line-spacings for datacomprising the newdatabase.

New edition Magnetic Anomaly Map and Grids▼ ▼

usGEONews


MODIS UpdateThe Moderate Resolution Imaging Spectrometer (MODIS) instrument onboard the TERRA and AQUA satellites provides multi-spectral remotesensing data in 36 bands at 250 metre, 500 metre and 1000 metre spatialresolution, with day and night coverage. Geoscience Australia’s remotesensing unit (ACRES) has been providing MODIS products since 2001(see AusGeo News 72).

ACRES provides on-line delivery of Near Real Time (NRT) Terra andAqua MODIS satellite imagery. This MODIS data is available at nocharge from the ACRES download site from the morning afteracquisition and the following seven days. Older MODIS imagery isavailable from ACRES’ archive. Details of the product specifications andthe ordering procedure for the MODIS product are outlined atwww.ga.gov.au/acres/prod_ser/modisprice.htm.

MODIS data aids mapping of burnt areasBurnt area maps are useful in developing appropriate mitigationstrategies, by building fire history of a given area over a period of time,which is essential for planning and executing controlled burning toreduce fuel loads.

From September 2004, ACRES has offered MODIS data in ProductData Set (PDS) format. PDS files contain MODIS data in raw form with aminimal amount of processing such as Read Solomon correction,descrambling and packet recovery for various instruments streams. PDSdata are useful to expert users who can implement their own algorithmsto derive thematic products. A practical example is burnt area maps,which extends the current hot spot information provided daily bySentinel at www.sentinel.csiro.au and Firewatch at www.firewatch.dli.wa.gov.au.

Geoscience Australia introduced PDS data in support of a projectinitiated by Western Australia’s Department of Land Information (DLI) incollaboration with the Fire & Emergency Services Authority of WesternAustralia. The project was funded under the Natural Disaster MitigationProgram initiated by the Commonwealth Department of Transport andRegional Services.

This arrangement allows DLIto access continental coverage ofMODIS data (via GeoscienceAustralia’s Alice Springs downlinkfacility) for natural disastermitigation and emergencymanagement. It also provides vitalbackup for the Western AustralianSatellite Technology andApplications Consortium receiverthat DLI use to derive burnt areamaps of Western Australia and theNorthern Territory. This data isavailable free of cost to registeredusers from Geoscience Australia’sMODIS web siteacs.auslig.gov.au/modis_data.MODIS PDS data size ranges from800 MB to one GB depending onthe pass length.

Landsat data is now evenmore affordable and accessibleto users as prices haverecently been reducedfollowing a review of the costsof transfer. The pricereductions are primarily theresult of efficiency gains atGeoscience Australia’s remotesensing unit (ACRES) throughreduced processing times,online ordering fordistributors, and, automaticgeneration of ortho-correctedproducts. They are also inaccord with theCommonwealth Government’sPolicy on Spatial Data Accessand Pricing.

Landsat 7 satellite SLC-Off/On composite productsGeoscience Australia has recently released Landsat 7 composite imagerywhich is a combination of two separate Landsat scenes acquired on differentdates. One scene is the more recently acquired SLC-Off data that containssmall gaps in the data due to a malfunction of the satellite's Scan LineCorrector on 31 May 2003 (see AusGeo News 74). The other scene is fromdata acquired before this date which contains no gaps (SLC-On data). Themore recent SLC-Off data is used as the primary data source of thecomposite product, with the older SLC-On data used to fill any small gaps.

When ordering a Landsat 7 ETM+ SLC-Off/On composite product,customers will need to identify acquisition dates for both the SLC-Off dataand SLC-On data. For the best result, dates need to be chosen from similarseasons and with minimal transient data such as clouds, fires, snow or otherground cover changes.

These SLC-Off/On composite products will only be available as ortho-corrected products in Fast L7A format. A full scene SLC-Off/On compositeproduct has a recommended retail price of $900.

ACRES is currently looking into the development of composite productsusing data acquired from successive SLC-Off passes to minimise the temporaleffects of using an older SLC-On scene. These products should be availablein early 2005.

For more information phone ACRES Customer Service on +61 2 6249 9779 or e-mail [email protected]

Landsat data PRICES REDUCED

ausgeo - ga.gov.auausgeo news december 2004 issue no. 76 editors jeanette holland, steve ross...

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