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Supervising Scientist Environmental Monitoring Program
In this form of monitoring, effects of runoff water from the Ranger uranium minesite on receiving waters are evaluated using responses of aquatic animals exposed to creek water. The responses of two test species are measured over a four-day period:
Toxicity monitoring test sites are located on Magela Creek, upstream of the mine site (control site) and just below gauging station GS8210009, some 5 km downstream of the mine (exposed site). At the end of each 4-day test, the mean number of eggs per snail pair and mean number of fish surviving per replicate, are noted and compared for each of the upstream and downstream sites. Specifically, when data from the downstream site are subtracted from those at the upstream site, a set of 'difference' values can be derived. These difference values may be compared statistically for different parts of the time-series. For example, 'difference' data for the wet season of interest may be compared with those from previous years; if they differ significantly, using a Student's t test, it may indicate a mine-related change. Technical details of the statistical design and data analysis procedures may be found in Humphrey et al (1995) and in Appendix 4, volume 2 of ANZECC and ARMCANZ (2000). Additional developmental work may be found in the Supervising Scientist 2000-2001 Annual report (pp 49-50) section 3.1.4.
Toxicity monitoring using creekside techniques (creekside monitoring, figure 1A) has provided the primary means for toxicity monitoring since such testing commenced in the 1991-92 wet season. Creekside monitoring uses water pumped from the creek to creekside testing stations where header tanks provide continuous water flow to test chambers. In the 2006-07 wet season, a two-year research project commenced comparing creekside monitoring tests to those conducted in situ using floating test chambers secured in the creek (so-termed 'in situ monitoring', figure 1B). In situ monitoring has the potential to greatly reduce test infrastructure and staff resources whilst providing a portable and more continuous toxicity test.
Because of the additional resources required for the comparative evaluation of creekside and in situ monitoring techniques over the 2006-07 and 2007-08 wet seasons, a decision was made to focus primarily on the freshwater snail test for the evaluation. The fish larvae response is much less sensitive than the snail response (toxicologically) to Ranger mine waste waters and suffers inherent natural high mortality rates at the upstream control site. While some limited fish larvae testing is being conducted, this is confined to the upstream site only. Thus for the 2006-07 and 2007-08 wet seasons, assessment of the effects of Ranger mine water dispersion to Magela Creek in the SSD's routine stream monitoring program is being conducted just with the freshwater snail test.
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Figure 1A eriss staff conducting toxicity monitoring of freshwater snails and fish fry at a creekside station on Magela Creek. |
Figure 1B Toxicity monitoring using in situ floating test containers. |
Since about 1996, toxicity tests have been performed approximately every other week during the wet season. Tests usually commence in December and cease in early April, the period of significant creek flow in Magela.
The results of the toxicity monitoring tests are plotted as part of a continuous time series of actual and 'difference' data in figure A for snail egg production, and in figure B for larval fish survival. As described in section 1.1 of the background document, part of this time series of data was acquired by Energy Resources Australia (ERA) because of the earlier intent for the company to routinely conduct chemical and biological monitoring. As part of the technology transfer process, including data quality assurance, eriss conducted from time to time tests in parallel with ERA. In the event, data quality for the fish tests conducted by ERA (1996-2000) was generally not sufficient to incorporate in the time series, apart from the results of the second test of 1999-00 shown in figure B (ERA data). ERA's snail egg production data were generally suitable for reporting, and in the time series shown in figure A, ERA provided data for the first, second and third tests of 1995-96, all tests for 1997-98, 1998-99 and 1999-00, and for the fifth, sixth, seventh and eighth tests of 2000-01.
Corrections and amendments to the time series of snail egg production and larval fish survival data depicted in figures A and B respectively have been made from time to time as a consequence of transcription errors discovered in the data and the implementation of new data validation and acceptance criteria procedures. These changes are detailed in the various Supervising Scientist Annual reports as issues arise.
So far in the 2007-08 wet season, six toxicity monitoring tests using snail egg production have been conducted (3-7 December 2007, 17-21 December 2007, 31 December 2007 - 4 January 2008, 14-18 January 2008, 28 January - 1 February 2008 and 11-15 February 2008). The first test relied on in situ monitoring only, due to insufficient water depth beneath the creekside monitoring pumping stations (located in the creek channel). This demonstrates an additional advantage of in situ monitoring over creekside monitoring for periods of low flow for which creekside infrastructure is unsuited. Creekside monitoring, however, was conducted in all other test weeks. The results for the initial in situ test and subsequent five creekside tests are plotted as part of a continuous time series of actual and 'difference' data in Figure A.
Snail egg production for the six tests conducted to date was similar at upstream and downstream sites, although egg numbers were reduced at both sites during the sixth test. Nevertheless, the pattern of egg production across all six tests is similar to that observed in previous wet seasons; importantly, the resulting upstream-downstream difference values plot around the running mean (since 1991-92 wet season) and are within the maximum and minimum range recorded over this time (figure A). From the collective creekside and in situ results to date (figure A), no adverse effects on freshwater snails of water discharged from the Ranger minesite to Magela Creek are evident.
The comparative creekside versus in situ monitoring using the snail egg production test (see background text above or Supervising Scientist Annual report for 2006-2007 (pp 56-58 section 3.3 ) has continued in the 2007-08 wet season, the first comparative test being conducted between 17-21 December 2007. To date, five comparative tests have been conducted and the preliminary results show concordance in snail egg production response between creekside and in situ testing conditions (results not shown at this stage). Such comparative testing will continue for the remainder of the wet season. Prior to the next (2008-09) wet season, results from the comparative tests conducted during the 2006-07 and 2007-08 wet seasons will be analysed to determine if in situ monitoring can replace creekside monitoring.
Creekside and in situ monitoring using larval fish survival at upstream and downstream sites has not continued in the 2007-08 wet season due to the additional resources required to conduct the comparative creekside versus in situ snail egg production tests.
Parallel creekside and in situ testing were conducted in 2006-07, comparing egg production in freshwater snails exposed to upstream and downstream creek waters. Up until late February 2007, four comparative four-day tests were conducted every-other-week. Severe flooding occurred in Magela Creek in late February and early March 2007 which led to loss of critical creekside infrastructure, preventing further creekside testing in that wet season (figure 2). However, it was possible to resume in situ monitoring and after the flood event, testing using the in situ technique continued until an additional three tests were completed. Assessment of the effects of Ranger mine water dispersion to Magela Creek in this report is reliant on the results of both creekside (tests 1-4) and in situ (tests 5-7) testing.
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Figure 2 Flood damage to the upstream creekside toxicity testing infrustructure, March 2007. (A) flood waters 1.5m deep at the creekside laboratory. (B) Pontoon used for pumping water to the creekside laboratory being salvaged, the pontoon was upturned during the flood (see inset). |
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The results of the seven toxicity monitoring tests conducted in 2006-07 for snail egg production are plotted as part of a continuous time series of actual and 'difference' data in Figure A. Descriptions of the sources of creekside data and data quality issues are provided in the Supervising Scientist's Annual Report for 2001-02 (20-22), section 2.2.3 and web site.
Snail egg production at upstream and downstream sites was generally similar across all seven tests, and resembles the pattern of egg production observed in previous wet seasons. The exception to this is the discrepancy in egg production observed in the first test for the season (Figure A), giving rise to the largest 'difference' value ever recorded over the 16 wet season history of creekside monitoring. Parallel creekside and in situ snail egg production results for the first four tests of 2006-07 are shown in Figure C (below). While the magnitude of egg production at both sites was greater in the in situ tests, a similar pattern of egg production response was observed to that shown in the creekside results. In the first in situ test conducted for 2006-07, there was no discrepancy observed in egg production between the two test sites. Considering the similar pattern in egg production observed between the two treatment types (creekside and in situ) in 2006-07, it would appear that snail production at the downstream creekside station was anomalously high during the first test. While creek water levels were quite low during the first test for 2006-07 (which commenced on 1st January 2007), corresponding spot water chemistry data collected during this test as part of the SSD's routine monitoring program do not indicate any significant elevation of analytes at this site nor any atypical discrepancies between the two creek sites that might explain the unusual creekside result.
Figure C Comparison of freshwater snail egg production for routine creekside monitoring and in situ toxicity monitoring, 2005-06 and 2006-07 wet seasons. In 2005-06, in situ testing was confined to just the upstream (control) site.
Thus the increased snail egg production observed at the downstream creekside station during the first test of the 2006-07 wet season does not appear to be mine-related. From the collective creekside and in situ results, it is concluded that no adverse effects of water discharged from the Ranger minesite to Magela Creek were observed during the 2006-07 wet season on freshwater snails.
Over a decade of creekside monitoring test data have been obtained since 1991-92 (Figure 6) using the established creekside protocols and infrastructure. It is thus critical to ensure that the proposed in situ method yields comparable results before it can be phased in as the sole procedure in the future. To date, results from in situ toxicity monitoring are encouraging in terms of concordance of snail egg production between upstream and downstream sites, and the similarity of results with corresponding creekside results (Figure C). While the magnitude in egg production may be greater in situ test containers, the important test end-point is the corresponding upstream-downstream difference values, and these values, so far, appear to be similar between both creekside and in situ conditions.
Seven creekside tests were conducted in the 2005-06 wet season (2-6 January 2006, 16-20 January 2006, 30 January-3 February 2006, 13-17 February 2006, 27 February-3 March 2006, 20-24 March 2006 and 3-7 April 2006). Significant pump failure occurred during the fourth test at the upstream site, to the extent that the test did not meet acceptance and validity criteria. While the data for this test are displayed in the accompanying figures, they are not used in formal statistical analysis to detect and assess potential mining impact. (By convention, the upstream-downstream 'difference' value is omitted from the graphs of test organism responses to signify an invalid test.)
Amongst the snail tests, egg production at upstream and downstream sites was similar across all tests conducted for the wet season (figure A). The results also resemble the pattern of egg production observed in previous wet seasons with the possible exception of the relatively low egg production observed downstream in the fifth test. This value was a consequence of significantly lower (P<0.05) egg production observed in the duplicate water drawn from the west bank of the creek at the downstream site (mean of 54 eggs per snail vial), relative to the corresponding duplicate water drawn from the east bank at this site (107 eggs per snail vial) and from the two duplicate waters drawn from the upstream site (117 and 123 eggs per snail vial). Corresponding spot water chemistry data collected during this test as part of the SSD's routine monitoring program do not indicate any significant elevation of analytes at this site. Additional water chemistry data, together with continuous datasonde records for key parameters including conductivity and pH, were also collected during this creekside test and results, similarly, do not show any major discrepancies in water quality between the east and west bank sites. Thus the reduced snail egg production observed at the downstream west bank site during the fifth test does not appear to be mine-related.
Using the snail egg production data shown in figure A, 'difference' values for 2005-06 were compared with those from previous years. No significant difference was found (P>0.05).
Across all fish tests, larval fish survival at upstream and downstream sites resembled the pattern of fish survival observed in previous wet seasons with, typically, reduced survival at the upstream site relative to the downstream site (figure B).
In both the web site description above for the 2004-2005 wet season and in the Supervising Scientist Annual Report for 2004-2005, is was noted that fish survival 'difference' (upstream-downstream) data for the two periods 1991/92-96/97 and 1999/00-04/05 were significantly different from one another as a consequence of the reduced larval fish survival at the upstream control site in the period 1999/00-04/05. (Possible causes are discussed in the Supervising Scientist Annual Report for 2002-2003.)
With the inclusion of 2005/06 data, the same significant difference, 1991/92-96/97 versus 1999/00-05/06 (P=0.005), was observed. However, when 'difference' results for 2005/06 were compared separately with results for the two time periods (1991/92-96/97 and 1999/00-04/05), no significant differences (P>0.05) were found in either case. This result indicates that larval fish survival at the downstream relative to upstream (control) site in Magela Creek during 2005/06 was consistent with the same relative survival rates observed in previous wet seasons.
From the collective creekside results, it was concluded that there were no adverse effects of dispersed Ranger mine waste waters to Magela Creek on either of the creekside test species over the 2005-06 wet season.
In the 2005-06 wet season, experiments commenced to evaluate the effectiveness of conducting the same snail and fish tests inside floating cages, in situ in Magela Creek, to provide a cost effective way of providing almost continuous monitoring of water quality. Preliminary studies were conducted to determine a suitable design of holding vessels for test organisms, and to assess the responses of freshwater snails (reproduction) to a variety of holding conditions and feeding regimes. This investigation has also entailed a comparison of egg production in snails held parallel in situ and in creekside tests at the upstream site. For the three comparative tests completed during the 2005-06 wet season, similar responses in snail egg production were observed between the two test conditions. In 2006-07, more extensive studies will be conducted to confirm the applicability and robustness of the method upstream and downstream of Ranger.
Eight creekside tests were conducted in the 2004-05 wet season (27-31 December 2004, 10-14 January 2005, 24-28 January 2005, 7-11 February 2005, 21-25 February 2005, 7-11 March 2005, 21-25 March 2005 and 4-8 April 2005.) Only five tests were conducted using larval fish, there being too few fish larvae available to conduct the fourth, sixth and seventh tests.
Amongst the snail tests, egg production at upstream and downstream sites was similar across all tests conducted for the wet season (figure A). Using the data shown in figure A, 'difference' values for 2004-05 were compared with those from previous years. (The difference data shown and subsequently used in statistical analyses are those for valid tests only.) No significant difference was found (P>0.05).
The lack of fish larvae available in the fourth, sixth and seventh tests was a result of high mortality in the developing eggs held in broodstock waters at the Jabiru Field Station laboratories. Broodstock waters are taken from Magela Creek upstream of Ranger. Broodstock waters collected for these (failed) tests generally coincided with periods when flow in Magela Creek was unusually low. It is possible that during these periods, high water temperatures and insolation are conducive to the build up of micro-organisms that are harmful to fish larval development. This issue is being investigated, together with possible solutions to prevent future occurrences of such test failures.
Across all fish tests, larval fish survival at upstream and downstream sites was similar (figure B), apart from reduced survival at the upstream site relative to the downstream site during the third creekside test in particular (an observation commonly noted in previous years for this test species).
In both the web site description above for the 2003-2004 wet season and in the Supervising Scientist Annual report for 2003-2004 (29-32), section 2.2.3, is was noted that fish survival 'difference' (upstream-downstream) data for the two periods 1991/92-95/96 and 1999/00-03/04 were significantly different from one another as a consequence of the reduced larval fish survival at the upstream control site in the period 1999/00-02/03. (Possible causes are discussed in the Supervising Scientist Annual report for 2002-2003 (pp 31-33), section 2.2.3.) Note that prior to the present (May 2005), larval fish survival ascribed and depicted for 1995/96 is in error (eg 2003-2004 wet season results reported on this web site and in previous Supervising Scientist Annual reports). The actual wet season for which these data were gathered is the 1996/97 wet season; no larval fish survival data are available for the 1995/96 wet season.
With the inclusion of 2004/05 data, the same significant difference, 1991/92-96/97 versus 1999/00-03/04 (P=0.004), was observed. When 'difference' results for 2004/05 were compared separately with results for the two time periods (1991/92-96/97 and 1999/00-03/04), then:
This result indicates that larval fish survival at the downstream relative to upstream (control) site in Magela Creek during 2004/05 was consistent with the same relative survival rates observed in the previous five wet seasons.
From the collective creekside results, it was concluded that there were no adverse effects of dispersed Ranger mine waste waters to Magela Creek on either of the creekside test species over the 2004-05 wet season.
Eight creekside tests were conducted in the 2003-04 wet season (29 December 2003-2 January 2004, 12-16 January 2004, 26-30 January 2004, 9-13 February 2004, 23-27 February 2004, 8-12 March 2004, 22-26 March 2004 and 5-9 April 2004.) Only seven tests were conducted using larval fish, there being too few fish larvae available to conduct the final, eighth test.
The seventh test, using both test species and conducted in the period 22-26 March 2004, coincided with the Ranger drinking water incident. After results were acquired for this (seventh) creekside test, it was extended for an additional 4-day period, 26-30 March, using the same test organisms (fish and snails). This test is termed the 'seventh-extended test', results for which are depicted in figures A and B as the eighth set of actual data counts for the wet season (while the results of the eighth snail test are depicted in figure A as the ninth set of such data points). For the seventh-extended snail test, fresh egg-laying chambers were used (containing none of the previously-laid egg masses). Because the same test animals were employed in both tests, neither fish nor snail results for this extended period are strictly valid for a statistical comparison against other test results as there is lack of independence. Nevertheless, the results are certainly indicative of any potential water quality impacts.
Amongst snail tests, egg production at upstream and downstream sites was very similar across all tests conducted for the wet season (figure A). Using the data shown in figure A, 'difference' values for 2003-04 were compared with those from previous years. (The difference data shown and subsequently used in statistical analyses are those for valid tests only.) No significant difference was found (P>0.05). The results for the seventh-extended test, while not included in the formal statistical analysis, lie well within the range of variability observed in the current and previous years (figure A).
There was a lack of fish larvae in the seventh creekside test with which to run a valid test so that only 3 replicate fish tanks, each holding 10 fish larvae, could be used at each of the two creekside stations instead of the normal 6 replicate tanks. While results for fish larvae arising from the seventh and 'seventh-extended' test are plotted, the 'difference' values for both tests are not plotted (per convention to signify their invalid nature, figure B).
Across all fish tests, survival at upstream and downstream sites was similar (figure B). There was some reduced larval fish survival at the upstream site relative to the downstream site, but this was not as marked as in previous years (particularly the period 1999/00 to 2002/03, figure B). In the Supervising Scientist Annual report 2002-2003 (pp 31-33), section 2.2.3 it was noted that 'difference' (upstream-downstream) data for the two periods 1991/92-95/96 and 1999/00-02/03 were significantly different from one another as a consequence of the reduced larval fish survival at the upstream control site in the period 1999/00-02/03. (Possible causes are discussed in the Report.) With the inclusion of 2003/04 data, the same significant difference was observed (1991/92-95/96 vs 1999/00-03/04, P=0.003). However, when 'difference' results for 2003/04 were compared separately with results for the two time periods (1991/92-95/96 and 1999/00-02/03) no significant differences were found.
The results for the seventh-extended fish test that was conducted over the period of the Ranger drinking water incident, while not included in the formal statistical analysis, lie well within the range of variability observed in the current and previous years (figure B). In particular, fish survival was found to be consistently high at the downstream site over the 8-day period of both consecutive tests.
From the collective creekside results, it was concluded that there were no adverse effects of dispersed Ranger mine waste waters - including contaminated drinking water - on either of the creekside test species over the 2003-04 wet season.
Eight creekside tests were conducted in the 2002-03 wet season (16-20 Dec 2002, 30 Dec 2002 - 3 Jan 2003, 13-17 Jan, 27-31 Jan, 10-14 Feb, 24-28 Feb, 10-14 Mar and 24-28 Mar).Using the data shown in figures A and B , 'difference' values for 2002-03 were compared with those from previous years. (The difference data shown and subsequently used in statistical analyses are those for valid tests only.). Snail egg production at upstream and downstream sites was very similar across all tests (figure A ). Moreover, the results of statistical analysis showed no significant difference in the 'difference' values of 2002-03 data compared with data from previous years (P >0.05).
Larval fish survival was high at both upstream and downstream sites for the first, third, fifth, sixth and seventh tests (figure B ). In the second, fourth and eighth tests, fish survival at the downstream site was relatively high but was low at the upstream site. Poor upstream (control) survival has also been observed in previous years (figure B ); the discrepancy in larval fish survival rates between upstream and downstream sites on these occasions was noted and discussed in the Supervising Scientist Annual report 2002-2003 (pp 31-33), section 2.2.3. Natural changes in water quality associated with different intensity wet seasons, as well as exposure to additional billabong outflow water at the downstream site were presented as possible causes of the discrepancy. Nevertheless, the results indicate that there were no adverse effects of mine waste waters on either of the creekside test species over the 2002-03 wet season.
Over the December 2001 to April 2002 period, 7 valid snail and 4 valid fish tests were conducted. Using the data shown in figures A and B , 'difference' values for 2001-02 were compared with those from previous years. The results for the snail egg production analysis showed no significant difference in the 'difference' values of 2001-02 data compared with data from previous years (P >0.05). For larval fish survival data, similarly, no significant difference in the 'difference' values of 2001-02 data were observed when these data were compared with data from the period 1992 to 2000 (P >0.05). (Larval fish survival data from 2001 were not included in the analyses because relatively poor survival was observed in this year at the control site - see Supervising Scientist Annual report 2000-2001 (pp 21-23), section 2.2.3 for details.)
From these results, it is concluded that there were no adverse effects of mine waste waters on either of the creekside test species over the 2001-2002 wet season.
Humphrey CL, Faith DP & Dostine PL 1995. Baseline requirements for assessment of mining impact using biological monitoring. Australian Journal of Ecology 20: 150-166.