Hawkesbury-Nepean River Environmental Monitoring Program
Hawkesbury-Nepean River Environmental Monitoring Program
Hawkesbury-Nepean River Environmental Monitoring Program
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Sites upstream and downstream of dams, and at reference sites in the<br />
<strong>Hawkesbury</strong>-<strong>Nepean</strong> <strong>River</strong><br />
An assessment of the effects of dams and weirs on diatom and macroinvertebrate<br />
assemblages of the <strong>Hawkesbury</strong>-<strong>Nepean</strong> <strong>River</strong> system was undertaken by<br />
AWT(1998) and Growns and Growns (2001). As part of the SCA’s Woronora<br />
<strong>Environmental</strong> Flows Project, sampling of macroinvertebrates (and diatoms) was<br />
repeated in 2002 at the same sites (with some additional sites in the Woronora<br />
catchment) and using (as far as possible) the same design as Growns and Growns<br />
(2001). This project has continued to sample macroinvertebrates over the intervening<br />
time period, meaning that some sites have now been sampled over a period of<br />
approximately 12 years (with a gap of about 5 years between 1997 and 2002).<br />
Sampling in the later period has been undertaken consistently by Ecowise<br />
<strong>Environmental</strong> under contract to the SCA (Ecowise <strong>Environmental</strong> 2007). A list of the<br />
monitoring sites considered in this section is included in Table A5.1.1 (Appendix 5).<br />
A complicating factor in the analysis of these data is the different organisations and<br />
slightly different methodologies used to collect the data in different time periods.<br />
Macroinvertebrate samples collected by Sydney Water/AWT were generally sampled<br />
twice a year in autumn and spring using the methodology described by Chessman<br />
(1995), AWT (1998) and Growns and Growns (2001). Samples collected by Ecowise<br />
<strong>Environmental</strong> as part of the SCA’s Woronora <strong>Environmental</strong> Flows Project were also<br />
usually sampled twice a year in autumn and spring but were collected using<br />
AusRIVAS protocols. The latter methodology is further described by Turak et al.<br />
(1999, 2004) and Ecowise <strong>Environmental</strong> (2007).<br />
In order to compare the results from these programs, (at least) two assumptions<br />
need to be made, i.e. that:<br />
• the taxonomy is consistent between the two organisations and over the two main<br />
periods of sampling<br />
• the families or genera collected in samples are not greatly affected by slight<br />
differences in the sampling methodology used by the two organisations.<br />
The first assumption was addressed by matching the taxonomic levels used by<br />
Growns and Growns (2001) with that of Sydney Water/AWT and Ecowise<br />
<strong>Environmental</strong>. This involved pooling of some genera into higher taxonomic<br />
categories (e.g. subfamilies of the Chironomidae) to achieve consistency with earlier<br />
taxonomic resolutions. The taxonomy used is described further in Table A5.1.2<br />
(Appendix 5). It still relies, however, on consistent identifications by individual<br />
taxonomists/scientists (i.e. a lack of individual operator effects). The second<br />
assumption has been investigated previously by Growns et al. (1997, 2006) who<br />
found similar results were obtained when four live-sorting methods were used in<br />
rapid biological assessments.<br />
What these differences in sampling methodologies mean, however, is that any<br />
putative temporal changes over time are confounded by changes in sampling<br />
organization, sampling protocol and operator differences (assuming they are still<br />
sampling the same site) 12 . This issue is returned to later in the discussion.<br />
The impacts of river regulation have already been assessed by Growns and Growns<br />
(2001) and Ecowise <strong>Environmental</strong> (2007). The objective of this section is therefore<br />
12 Although every attempt was made to relocate the sites sampled by Dr Growns and<br />
described by AWT (1998) and Growns and Growns (2001), there remains the possibility<br />
that the stream reach sampled may be slightly different (but most likely within 100’s of<br />
metres) from the site originally sampled.<br />
<strong>Hawkesbury</strong> <strong>Nepean</strong> <strong>River</strong> <strong>Environmental</strong> <strong>Monitoring</strong> <strong>Program</strong>: Final Technical Report 33