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Full report

• SSR 118 - The impact of historical mining operations at Mount Lyell on the water quality and biological health of the King and Queen River catchments, western Tasmania. (PDF 6.65 MB)

Separate sections

• Preliminary pages (PDF - 538 KB)
• Chapters 1-3 (PDF - 1.8 MB)
• Chapters 4-7 (PDF - 2.4 MB)
• References and Appendices (PDF - 1.9 MB)

Executive summary

Mount Lyell, western Tasmania, a 100 year old copper mining operation in which large quantities of sulphide rich ore rock have been both exposed to weathering and discharged as tailings into the Queen and King Rivers, is the subject of a research program evaluating environmental impacts of resulting acid mine drainage (AMD) and remediation options. A survey of biological and water quality conditions of streams in the Mount Lyell region was conducted and a long-term biological and water quality monitoring program was designed based on the survey results and related data.

In order to identify ecological targets for long-term remediation of the Mount Lyell mine lease, a total of 32 reference ('least disturbed') and monitoring sites were established in streams in major catchments of the region. Riffle macroinvertebrates at all sites were sampled in four seasons in 1995/96 (winter and spring 1995, summer and autumn 1996) using the National River Health Program (NRHP) rapid assessment protocol (RAP). A suite of environmental variables was also measured at each site including water quality variables. A number of sites were also sampled for macroinvertebrates quantitatively. A survey of stream fish populations was conducted in summer-autumn 1996, by backpack electrofishing.

The macroinvertebrate communities of reference sites were diverse and characterised by a high abundance of stonefly, mayfly, caddisfly and beetle larvae. Despite a history of severe stream sedimentation and poor water quality (with low pH and high metal concentrations), all AMD-polluted sites supported a macroinvertebrate fauna, characterised by low abundances of chironomid and scirtid beetle larvae and oligochaetes (worms). Relationships between biological and water quality variables were examined and highlighted the complex nature of habitat alteration in AMD-affected sites typified by substrate concretion and sedimentation. Ordination and classification of the RAP sample data revealed four primary groups of reference sites in the region. A RIVPACS (River Invertebrate Prediction and Classification Scheme) model (MLRIVPACS I) was developed to identify a faunal community suitable as a remediation target for each AMD-affected stream site. Assessment of sites in the Queen and lower King Rivers using the MLRIVPACS I model indicated that they were all highly or extremely impacted. A single site in the King River upstream of the Queen River junction was assessed as mildly impacted by hydroelectric power station operations.

A variety of quality assurance aspects of the RAP and quantitative sampling protocols were also examined. Relationships between data derived from live-picked RAP samples and their reconstituted residues were evaluated, as well as the influence of inter-operator and inter-riffle variability on the classification of river sites. Relationships between estimates of the mean, as well as the power to detect differences, and the number of quantitative sample units were also examined as a basis for the design of the long-term monitoring program.

A few streams in the Queen River catchment supported populations of introduced brown and rainbow trout. Tributaries of the lower King River were found to support three native fish species whose abundance and presence decreased with distance from Macquarie Harbour. These data, combined with data on fish ages, indicated that recruitment of native fish into streams of the Macquarie Harbour catchment occurs on an annual basis; that recruitment into the King River has occurred previously but has recently ceased, possibly due to changes in flow regime related to HEC operations; and that the galaxiid species only occur in tributaries within 5 km of the King River mouth. Thus water in the King River has occasionally been of sufficiently high quality to allow episodic migration of juvenile galaxiids and eels into the lower King River during the last 10 years.

A boat-mounted electrofishing survey was conducted. No fish were captured in the lower King River, in contrast to a high abundance and diversity of species found in the lower Henty River with similar sampling effort. Thus there appear to be no resident fish in the lower King River.

Water quality data for the Queen and King River catchments were reviewed. Strong correlations between AMD-sourced pollutants were observed (copper, manganese, iron, sulphate and pH). Relationships of analyte means, medians and standard deviations and sampling frequency were examined. These indicated that, for both the lower King and Queen Rivers, sampling frequencies greater than four hourly would significantly distort estimates from 'true' values. A water monitoring program based on high frequency recording of conductivity was recommended, coupled by a stratified water analysis program to derive relationships between conductivity and pollutant concentrations under a range of flow conditions. A minimal water quality and biological monitoring program is described, aimed at detecting long-term recovery of the Mount Lyell region streams from AMD pollution resulting from remediation activity and the distance from specified targets.