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Key departmental publications, e.g. annual reports, budget papers and program guidelines are available in our online archive.

Much of the material listed on these archived web pages has been superseded, or served a particular purpose at a particular time. It may contain references to activities or policies that have no current application. Many archived documents may link to web pages that have moved or no longer exist, or may refer to other documents that are no longer available.

Environment Australia Annual Report 1999-2000

Environment Australia, 2000
ISBN 0642450420
ISSN 1441-9335

Annual Report of the Supervising Scientist 1999-2000

3. Environmental research

The Environment Protection (Alligator Rivers Region) Act, 1978 established an Alligator Rivers Region Research Institute (eriss) to undertake research into the environmental effects of uranium mining in the Alligator Rivers Region and into other environmental issues elsewhere as appropriate.

eriss research is organised into two major programmes:

In addition eriss carries out general environmental research that meets specific needs identified by the Australian Government.

The programme of eriss is reviewed annually by the Alligator Rivers Region Technical Committee.

3.1 Environmental Impact of Mining

3.1.1 Programme objectives

The objective of the eriss programme on the environmental impact of mining is to provide advice, based on research and monitoring, to the Supervising Scientist and stakeholders on standards, practices and procedures to protect the environment from the effects of mining, particularly uranium mining in the Alligator Rivers Region.

In 1999-2000 the majority of research projects carried out within this programme were focused in one or more of the following areas:

3.1.2 Erosion and Hydrology

Temporal trends in erosion and hydrology characteristics for a post-mining rehabilitated landform at Energy Resources of Australia Ranger Mine

The aim of this research is:

An important part of rehabilitation planning for mines is the design of a stable landform for waste rock dumps or spoil piles at the completion of mining. To successfully incorporate landform designs in planning there is a need to be able to predict the stability of the final landform.

In the long term, weathering, soil forming processes, ecosystem development and even climate change may affect the stability of a rehabilitated landform. It is necessary to take these processes into account when predicting how a rehabilitated landform will behave in the long term, and whether it will meet rehabilitation objectives.

Rainfall data were collected from a site on a batter slope on the waste rock dump at Ranger; two sites on the waste rock dump of the abandoned Scinto 6 mine in the South Alligator River valley; two natural, undisturbed sites at Tin Camp Creek, Arnhem Land; and a natural site near Pit 1, at Ranger. The age of the surface at the batter site, the Scinto 6 sites, the Tin Camp Creek sites and the Pit 1 natural site are estimated to be approximately 0 years, 50 years, 2.1 million years and 3.2 million years respectively.

The erosion model SIBERIA was used to predict the stability of the proposed rehabilitated landform at Ranger. SIBERIA input parameter values were derived for each study site to determine the rate of change in parameter values with time under both concentrated flow and sheet flow conditions.

Soil and ecosystem development and surface armouring have a very clear temporal effect on erosion rate parameters (fig 3.1). The change is rapid and occurs within the first 50 years after mining is completed, after which the parameter values reach a stable equilibrium and remain relatively constant for millions of years. SIBERIA landform evolution simulations of a proposed rehabilitated landform at Ranger were conducted incorporating the rate of temporal change in input parameter values due to ecosystem development (fig 3.2). The erosion rate and valley development on the simulated landforms with input parameters that change with time decline relatively quickly in the short-term, particularly on the landform with sheet flow conditions where sediment movement stabilises almost completely after 50 years of simulation.

The incorporation of temporal change in input parameter values, due to soil and ecosystem development and surface armouring, into the SIBERIA model is a significant advance in landform evolution modelling.

Figure 3.1 SIBERIA input parameters (discharge exponent and erosion rate coefficient) at various times after rehabilitation at Ranger. Approximate lines of best fit for the concentrated flow and sheet flow conditions are also shown.

Figure 3.1

 

Figure 3.2 SIBERIA simulations for the originally proposed rehabilitated landform at Ranger at 1000 y for concentrated flow (1) and sheet flow (2) conditions incorporating temporal change. The predicted landform at 1000 y using initial zero year parameter values assumed to remain constant throughout the simulation period is also shown (3). Dimensions are in kilometres.

Figure 3.2

 

Suspended sediment loads in Swift Creek downstream of the Jabiluka mine

The investigation of suspended sediment loads in Swift Creek is part of a comprehensive project investigating the hydrology, sediment transport and sediment sources in the Swift Creek Catchment in which the Jabiluka mine is located.

The aim of this part of the project is to determine the suspended sediment loads within the Swift Creek catchment and what impact the development of the Jabiluka mine might have had on these loads.

Natural or background suspended sediment loads are the loads carried by the stream system in an undisturbed state. To determine these loads, long-term monitoring is required to gain an understanding of the effects of natural changes and variability in the catchment. There are limited data on background suspended sediment loads in the Swift Creek catchment. In 1998 eriss established a stream gauging network in the catchment by

installing gauging stations on the main channel downstream of the mine site (Swift Creek), on the main channel upstream of the mine site (Upper Main) and on the main right-bank tributary between these two stations (East Tributary) (fig. 3.3). Both Upper Main and East Tributary sites are above any influences that mining operations may have. Due to the braided and discontinuous nature of the West Branch channel it could not be gauged accurately. The rationale of the gauging network was that any significant changes measured in parameter values at the downstream Swift Creek site, not observed in the Upper Main and East Tributary sites, could be due to mine development activities. Parameters measured at these gauging stations for the 1998-99 and 1999-00 Wet season include rainfall, stage height, water velocity, discharge, channel geometry and bedload. Water samples were collected and analysed to determine total suspended sediment concentration as sand (>63 Ám) and mud (silt+clay <63 Ám >0.45 Ám), solutes (<0.45 Ám), turbidity, pH and conductivity. Table 3.1 shows, rainfall, runoff and total suspended sediment yield and specific suspended yield for the sites on Swift Creek and also results collected in the 1980s for nearby sand bed streams that were described as relatively undisturbed.

From the initial two years of data, the suspended sediment results show that for the Swift Creek site downstream of Jabiluka, there was a decrease in average mud concentration from 1998-1999 to 1999-2000 of 13 mg/L to 6 mg/L whilst there was an increase in average sand concentration of 25 mg/L to 30 mg/L from 1998-1999 to 1999-2000. The upstream sites did not exhibit the same changes suggesting that the source of these variations is from areas between the sites, perhaps the portal construction for Jabiluka. If this increase is due to portal construction in 1998 it would appear that the mud component, an increase of 7 mg/L, passed through the system in 1998-1999 and that the sand component, an increase of 5 mg/L, passed through the system in 1999-2000. This is a plausible explanation since mud is the most mobile component and there would be a time lag between mud and sand movement. However, the concentrations may not be totally due to portal construction which occurred in mid to late 1998. A large fire occurred in the western part of the catchment in September 1998 that would increase sediment movement into the stream system contributing to an increased sediment yield. It should also be stressed that the suspended sediment concentrations are all relatively small.

Suspended sediment loads have been determined for each of the gauging stations on Swift Creek for the 1998-1999 and 1999-2000 Wet seasons. There was a small change in average suspended sediment loads between the seasons, however, it is difficult to draw long-term conclusions based on two years of data. The suspended sediment loads are similar to undisturbed sand bed streams with similar sized catchments in the immediate vicinity. An initial suspended sediment baseline has been determined for various points along the Swift Creek catchment and data should continue to be collected to obtain a detailed understanding of catchment conditions as a basis for catchment management strategies.

Figure 3.3 Location of gauging stations on Swift Creek

Figure 3.3

Table 3.1: Total rainfall, runoff and Total Suspended Sediment yield and
Specific Sediment yield for the 3 Swift Creek sites and other nearby streams
Site Area (km2) Season Rainfall (mm) Runoff (ML) Total Suspended Sediment yield (t) Specific Sediment yield (t.km-2)
ET 8.3 1998-99 1776 7546 475 57.3
    1999-00 2069 8446 526 63.4
Koongarra 1 15.4 1981-82 1452 13173 489 31.8
    1982-83 1206 8216 439 28.5
UM 19 1998-99 1828 15703 659 34.7
    1999-00 2105 17422 653 34.4
SC 42.8 1998-99 1780 33760 1334 31.2
    1999-00 1997 34943 1364 31.9
7J 1 53.5 1981-82 1451 14413 505 9.4
Gulungul 1 61.9 1984-85 1781 31109 3607 58.27
    1985-86 967 14227 697 10.97
1 Data from Duggan K (1994) Erosion and sediment yields in the Kakadu region of northern Australia. International Association of Hydrological Sciences. Publ. No. 224, 378-383.

 

3.1.3 Radiological impacts of mining

Regional radon project

This project aims to provide detailed time-series data on concentrations of radon-222 (Rn-222) in air at various locations within the Alligator Rivers Region, over a time frame of several years. Radon arises from the decay of uranium which is present naturally in soils and rocks, and these data will be important in assessing the effects of uranium mining operations on radon levels in the region, both in providing baseline data and in calibrating and verifying predictive models. Until this project, few data were available on radon levels at sites more than a few kilometres distant from uranium mines.

During 1999-2000, a station was established at Mudginberri, bringing the total number operating in the region to four. It is now intended to operate the four stations at locations for one year intervals, at the end of which three will be moved to new locations (Mudginberri acting as a constant control station). Each station logs radon concentrations and relevant meteorological data (wind speed, direction and variability, air pressure and temperature, relative humidity, soil moisture and temperature, rain and sunshine rates).

Table 3.2 shows annual average Rn-222 concentrations obtained at Djarr Djarr, East Alligator Ranger station and at the former Nabarlek minesite, together with data from Jabiru Town and Jabiru East from an earlier project conducted by eriss. The averages obtained vary by more than a factor of ten, this is probably due to a combination of factors. For example, Djarr Djarr and East Alligator are close to large floodplain areas which are inundated with water for a large part of the year, this water cover being likely to reduce the radon emanation rate from these areas. The Nabarlek and Ranger minesite areas have higher uranium mineralisation than surrounding landscapes, and a conclusion of the 1990-1991 study was that 1 and 7 Bq/m3 of the average Rn-222 concentrations observed at Jabiru Town and Jabiru East, respectively, could be attributed to a contribution from the Ranger minesite. A combination of strategic location of measurement stations and statistical data analysis will be needed to separate the most important factors for each location.

3.1 4 Ecosystem protection

Effects of runoff from the disturbed Jabiluka mine site on macroinvertebrate communities of Swift Creek

Following disturbance of the mine site at Jabiluka in 1998 (land clearing, pond and portal construction) there was potential for the increased suspended solids loads that would arise in Swift Creek downstream of the mine in the ensuing 1998-99 Wet season, to adversely affect the aquatic biota. While eriss and Earth Water and Life Sciences (EWLS) had conducted some preliminary baseline sampling in the streams around Jabiluka in the previous (1997-98) Wet season, more strategic baseline sampling was initiated in the 1998-99 Wet season. The experimental design adopted in the 1998-99 Wet season enabled an assessment of the impact of mine disturbance on Swift Creek fauna, even though very few pre-disturbance data were available.

Benthic macroinvertebrates have been selected as a key ‘indicator' group to monitor and assess potential impacts upon aquatic ecosystems arising from the Jabiluka mine. Elsewhere in the Alligator Rivers Region, macroinvertebrates have been successfully used to detect and assess impacts arising from a variety of human-related disturbances, including effects of increased turbidity. In both the 1998-99 and 1999-00 Wet seasons, macroinvertebrate samples were gathered from sites in Swift Creek upstream and downstream of Jabiluka, and also from paired upstream and downstream sites in three adjacent streams currently unaffected by any mining activity at Jabiluka (control streams). Samples were collected from each site at three to four weekly intervals throughout each Wet season.

For each sampling occasion and for each pair of sites for a particular stream, a dissimilarity index was calculated. This index is a measure of the extent to which macroinvertebrate communities of the two sites differ from one another. A value of ‘zero' indicates identical macroinvertebrate communities while a value of ‘one' indicates totally dissimilar communities, sharing no common taxa. Research elsewhere in the Alligator Rivers Region has shown significantly ‘higher' dissimilarity values for locations upstream and downstream of point sources of disturbance compared to undisturbed control streams.

Table 3.2: Annual average Rn-222 concentrations in air measured at five sites
Site Measurement Period Rn-222 (Bq/m3)
Jabiru Town 1990-1991 24
Jabiru East 1990-1991 38
Nabarlek 1996-2000 75
DjarrDjarr 1997-2000 12
East Alligator 1998-2000 5.5

Figure 3.4 plots the paired-site dissimilarity values for Swift Creek and the three control streams for each of the sampling occasions of the past two Wet seasons. The figure shows that the mean dissimilarity value for each stream across both Wet seasons is approximately the same (~0.3) and that the values are reasonably constant over time. This indicates that increased suspended solids concentrations in Swift Creek downstream of Jabiluka in the Wet season were not sufficient to have adversely affected macroinvertebrate communities.

In the 1998-99 Wet season, turbidity in Swift Creek downstream of Jabiluka was approximately 6 NTU units above a relatively low background. In a portion of another Alligator Rivers Region stream affected by elevated suspended solids (not related to mining activities) and studied previously, adverse effects upon macroinvertebrate communities were observed at turbidities of between 30 to 60 NTU units above a low background. These latter results lend some support to the observations in Swift Creek of no observed biological effects.

Figure 3.4 Paired upstream-downstream dissimilarity values measured for macroinvertebrate community data in several streams near the Jabiluka mine in the 1998-99 and 1999-2000 Wet seasons. The dashed vertical line between the 7th and 8th sampling occasions delineates the two Wet seasons.

Figure 3.4

3.2 Wetland Ecology and Conservation

3.2.1 Programme objectives

In 1999-2000, the Wetland Ecology and Conservation programme, through its two sub-groups, ‘Ecology and Inventory' and ‘Risk Identification and Assessment', and now also through the National Centre for Tropical Wetland Research (nctwr), continued to undertake research, offer services and provide advice to the community and other clients.

The primary objective of the Wetlands Ecology and Conservation programme is to provide advice, based on research and monitoring, to key stakeholders on the ecology and conservation of tropical wetlands. This research is of direct relevance to assessing the environmental impact of mining in the Alligator Rivers Region as the part of the environment most at risk from mining are aquatic ecosystems including wetlands.

Sub-Objectives

Develop an information base for the wise use of tropical wetlands:

Identify and assess threats to tropical wetlands:

Provide advice and training for the wise use and conservation of wetlands:

Promote the research programme and its outcomes:

3.2.2 National Centre for Tropical Wetland Research

The National Centre for Tropical Wetland Research (nctwr) is an initiative announced by the Minister for the Environment and Heritage on 27 August 1998 to develop a collaborative venture between the Environmental Research Institute of the Supervising Scientist (eriss) and three university partners: James Cook University, Northern Territory University and the University of Western Australia. The Centre conducts research and training with the aim of providing information and expertise to assist managers and users of tropical wetlands to use these valuable habitats in a sustainable manner.

On 19 October 1999 a meeting of representatives from the four partner organisations was held to discuss the draft Heads of Agreement for the Centre. The Heads of Agreement document was finalised and signed by all parties on 16 December 1999. In early 2000 the Supervising Scientist, Dr Arthur Johnston, appointed Dr Max Finlayson as Director of the Centre, and arrangements began to establish an nctwr Board of Management.

On 31 March 2000 the nctwr Board of Management met for the first time and formally appointed the Hon. Bob Collins as Chair of the Board for a period of two years. The Board comprises Dr Arthur Johnston and Dr George Begg (eriss), Prof Richard Pearson and Dr George Lukacs (James Cook University), Assoc Prof Charles Webb and Prof Greg Hill (Northern Territory University), and Prof John Dodson and Dr Ian Eliot (University of Western Australia).

The Board of Management agreed that the Centre needed a proactive Advisory Committee to guide its activities and to advise on research and training priorities, research issues and directions. Eleven agencies and individuals, representing a variety of tropical wetland management interests across northern Australia, have been invited to join the Committee. The inaugural annual meeting of the Committee will be held in Darwin in September 2000, prior to the next Board of Management meeting.

In order to help fund nctwr operations in the initial stages of its establishment, all four partners have contributed an equal sum of ‘seed funding'. Corporate image development and promotion of the Centre is well underway with an nctwr logo and letterhead, business plan, capability statement and research strategy for the Centre developed to date. A training strategy is currently being discussed, and opportunities to submit joint research proposals and incorporate existing projects under the nctwr banner are being explored.

During May-June 2000, nctwr prepared for ASL2000, the 39th Annual Congress of the Australian Society for Limnology, held in Darwin on 7-10 July 2000. The Congress attracted 170 delegates from throughout Australia. Staff from eriss and the Northern Territory University collaborated with the Northern Territory Department of Lands, Planning and Environment to organise and sponsor the Congress. ASL2000 included the inaugural Australian Wetland Forum, which brought wetland scientists, managers and non-government organisations together to develop a strategy to ‘Stop and reverse the loss and degradation of Australian wetlands'.

3.2.3 Ecology and Inventory

Review of environmental management and impacts of mining in tropical Oceania

A review of environmental management of eleven major mining operations in northern Australia, Papua New Guinea and Irian Jaya was undertaken for the Tropical Wetlands of Oceania programme of World Wildlife Fund (WWF) Australia. The project provided an outline of the mining operations and their environmental management and evaluated the risks for wetlands downstream to assist WWF in developing collaborative environmental programmes with local communities and mining companies. Because of the different topography and rainfall regimes, the risks to wetlands from Australian mining operations were quite small compared with those in New Guinea.

The impact of Para grass on faunal biodiversity and ecosystem processes of wetlands in Kakadu National Park

Weeds are a major potential threat to wetlands and their control must be included in management strategies. A project assessing the impact of the exotic pasture species Para grass on the ecology of floodplain wetlands and the impact of herbicide control measures was completed. This was funded by the National Wetland Research and Development Programme and eriss and involved collaboration of Parks Australia North, Northern Territory University, Griffith University, University of Western Australia and eriss. The information obtained provides a basis for ecological risk assessment for this weed in Kakadu National Park and elsewhere. Workshops informing stakeholders of the outcomes are being held in July and August 2000. The study found that Para grass reduced plant biodiversity and increased biomass production which increases the potential risk of fires to fauna in the dry season. However, there were no adverse effects of Para grass or herbicide control measures used on the communities of aquatic invertebrates and fish. Food chain studies found that Para grass material did not enter the food chains of aquatic invertebrates and fish. Community metabolism studies indicated a potential increased risk of oxygen depletion in Para grass.

3.2.4 Risk identification and assessment

Several major projects commenced in 1999-2000 including an assessment of the toxicity of uranium to a local freshwater alga, the further development of a rapid bioassay for screening complex effluents for toxicity, and a predictive risk assessment of the potential impacts of cane toads to Kakadu National Park. The latter project is a joint venture between eriss and Parks Australia North. Several major projects were completed, two of which are described below.

Prevention of aquatic aluminium toxicity by naturally occurring silica: Field and laboratory evidence

Kadjirrikamarnda Creek (Gadji Creek), in northern Australia, receives groundwater seepage contaminated by water from the decommissioned Nabarlek uranium mine. The acidity of the groundwater has resulted in the release of aluminium (Al) from soil minerals. Thus, Al is usually present in Gadji Creek at concentrations well in excess of the Australian and New Zealand Environment and Conservation Council (ANZECC) water quality guideline value for the protection of aquatic ecosystems, as well as toxicity values for a large range of aquatic organisms. However, silica, which is present naturally in groundwater and Gadji Creek water, has previously been shown to bind to, and ameliorate the toxicity of Al to fish. Thus, it was hypothesised that silica in Gadji Creek could be reducing or preventing aquatic Al toxicity.

Laboratory toxicity tests on Gadji Ck water were carried out using three local aquatic organisms (purple-spotted gudgeon, Mogurnda mogurnda; green hydra, Hydra viridissima; freshwater cladoceran, Moinodaphnia macleayi) in August 1997 and September 1998, periods when groundwater influence to the creek was high. No toxicity was observed, even though total and filterable Al concentrations were approximately 18 and 7 times (1997), and 30 and 20 times (1998) the ANZECC Water Quality Guideline value (for < pH 6.5), respectively. However, silica concentrations were around 84 and 55 times the molar concentration of total Al, potentially explaining the absence of toxicity. To further understand this relationship, manipulative laboratory experiments were carried out in 1999-2000 to assess the effects of silica on the aquatic toxicity of Al. Specifically, the influence of silica on the acute toxicity of Al to the fish, M. mogurnda, in soft, buffered, low pH water was investigated. The laboratory results confirmed that elevated silica did in fact result in a reduction in Al toxicity. Subsequent speciation modelling indicated that bioavailable Al remained stable, regardless of the silica concentration, not supporting the hypothesis that Al-silicate complexation reduced Al toxicity. An alternate hypothesis, that silica actually inhibits Al uptake is proposed for further work. This project also demonstrates the importance of site-specific studies for ecological risk assessment. Mimosa pigra and its control in northern Australia and south-east Asia: A review and some recommendations

In 1999, a literature review on the effects, extent and control/management of the major wetland weed, Mimosa pigra, in northern Australia was compiled by the Wetland Ecology and Conservation section as part of a case study to apply a wetland risk assessment framework to a major wetland threat. This review has since been published as an Internal Report. Armed with this information, Dr Max Finlayson attended a workshop on the management of the Tram Chim National Park in the Mekong Delta, Viet Nam, in mid 1999, to provide advice on the management of Mimosa. The content of the presentation and details of recommendations are currently being published in the peer-reviewed journal, Wetlands Ecology and Management.

Following a recommendation for further advice and training, the Wetland Ecology and Conservation section coordinated a study tour of northern Australia in April 2000 by six wetland managers from the Mekong Delta. The tour was funded by the Northern Territory University's Asia Pacific Wetland Managers Training Programme. Staff from eriss and Parks Australia North, with various other wetland experts from the Top End of the Northern Territory presented and exchanged information on tropical wetland management with the visiting group. The purpose of the tour was to provide Viet Namese wetland managers with an opportunity to learn more about management of national parks, particularly in relation to weed control.

As a timely follow-up to the study tour, consultant Mr Michael Storrs visited Viet Nam for two weeks in May 2000 to spend time with local staff in Tram Chim National Park and U Minh Thuong Reserve, to develop a weed management strategy for these areas. The visit was again coordinated by eriss and a representative from the International Crane Foundation in Viet Nam, while funding was again provided under NTU's Asia Pacific Wetland Managers Training Programme. A draft weed management strategy for Tram Chim National Park and U Minh Thuong Reserve was developed and will be finalised over the next few months, with further discussions on implementation and progress expected.