River and stream water quality and ecology - Greater Wellington ...

River and stream water quality and ecology in the Wellington region: State and trends
the time of sample collection or, even, relocation of monitoring sites to
reaches where flow can be measured or better estimated.
A number of important aspects of stream health have not been monitored
routinely to date, or have only recently been incorporated into the RSoE
programme. These include fish community condition, macrophyte cover,
instream sedimentation and stream habitat quality. The lack of
information on these components has limited the scope of the overall
conclusions made in this report about the health of the region’s rivers and
streams. For example, as noted in Section 7.3, some RSoE sites
considered ‘degraded’ by traditional measures (eg, water quality and
macroinvertebrate community metrics) can have significant indigenous
fish values. The recent development of standardised protocols for
assessing freshwater fish populations (David et al. 2010; Joy & David in
prep) should be utilised to implement a formal fish monitoring programme
for the Wellington region. Similarly, national protocols have recently been
finalised that provide guidance on monitoring of instream sedimentation
(Clapcott et al. 2011) and stream habitat (Harding et al. 2009).
The most significant limitation in terms of RSoE reporting is the lack of
region-specific guidelines for water quality and ecological health that
cover the range of natural characteristics and values (eg, ecosystem health,
swimming, trout spawning, etc.) associated with the region’s rivers and
streams. As outlined in Section 3.1, natural catchment characteristics, such
as geology and elevation, result in variation in water quality, stream
habitat and aquatic communities. Evidence that region-wide application of
‘one size fits all’ national guidelines is not appropriate is provided by the
presence of DRP at concentrations above the ANZECC (2000) lowland
trigger value at some reference sites in the region. Work is currently
underway to develop region-specific guidelines for Greater Wellington’s
next Regional Plan that better reflect not only the natural diversity of river
and stream types in the Wellington region but also the range of values
these rivers and streams are managed for (eg, Ausseil in prep a–d;
Greenfield in prep a & b).
There are some significant knowledge gaps around the effects of specific
activities on river and stream health in the Wellington region (eg, exotic
forestry harvest and instream works such as gravel extraction and river channel
realignment/contouring), and the sources of high nutrient or sediment inputs
to some streams. The use of targeted, catchment-based monitoring and
investigations is recommended to address these knowledge gaps.
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