Appendix 9 Aquatic Ecology Review Memorandum - Greater ...
Appendix 9 Aquatic Ecology Review Memorandum - Greater ...
Appendix 9 Aquatic Ecology Review Memorandum - Greater ...
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MEMO<br />
TO<br />
COPIED TO<br />
FROM<br />
FILE<br />
DATE<br />
Christina Schierlitz<br />
Juliet Milne; Mike Thompson<br />
Alton Perrie<br />
WAR/11/0162<br />
18 November 2013<br />
ESci water quality and aquatic ecology review: Matahiwi Dam consent<br />
application (WAR110162)<br />
Introduction<br />
Qualifications and experience<br />
1. My name is Alton Clifford Perrie. I am employed as an environmental scientist (freshwater<br />
quality and ecology) by <strong>Greater</strong> Wellington Regional Council (GWRC). I have held this<br />
position for over nine years. I hold a Bachelor of Science in <strong>Ecology</strong> and a Master of<br />
Science in Freshwater <strong>Ecology</strong> (first class honours) from the University of Waikato.<br />
2. My areas of expertise are in surface water quality and freshwater ecology. At GWRC I am<br />
responsible for managing State of Environment programmes that monitor the Wellington<br />
region’s rivers, streams and lakes, including both the water quality and biological aspects of<br />
these programmes. As part of my role I also regularly provide technical advice on consent<br />
applications in regards to assessments of freshwater values and potential effects from<br />
proposed activities.<br />
Involvement in WAR110162 consent process<br />
3. I have reviewed the water quality and aquatic ecology aspects of the Matahiwi Farm Dam<br />
consent application and provided technical review comments to the GWRC Resource<br />
Officer (Christina Schierlitz). I also previously provided comments on some aspects of this<br />
application during its initial stages to Grant Kneebone (the GWRC Resource Officer<br />
processing the application at that stage) in late 2011.<br />
4. On 3 April 2013 I attended a prehearing in which the focus of my involvement was on fish<br />
passage upstream and downstream of the dam intake/harvest structure. This led to several<br />
follow up conversations and emails with Andrew Lamason (EAM) and Cameron Drury<br />
(Cheal) to further clarify information in regards to fish passage past this structure.<br />
1287853-V2 PAGE 1 OF 14
5. I have also visited the location of the proposed dam site (November 2011) and have<br />
undertaken a backpack electric fishing survey of the stream reaches above the proposed<br />
dam site.<br />
Scope of technical review<br />
Documents reviewed<br />
6. The reports directly relating to the application that I have consulted in whole or part to<br />
prepare this memo include:<br />
a) EAM Environmental Consultants 2011. Ecological assessment of effects for a<br />
proposed water retention dam on an un-named tributary of the Wakamoekau<br />
Stream, Waipoua River. Prepared for Rupert Handyside, January 2011.<br />
b) Cheal Consultants Ltd 2013. Matahiwi Farms Ltd: Proposed Water Harvesting<br />
Scheme (Assessment of Environmental Effects Report). Prepared for Rupert<br />
Handyside, November 2013.<br />
Area of focus<br />
7. This memo focuses on the technical aspects of the proposed Matahiwi Farm Dam activities<br />
in relation to water quality and aquatic ecology. In particular it includes comment on:<br />
a) The adequacy of the water quality and ecological information provided;<br />
b) The assessment of effects based on my understanding of the proposal;<br />
c) Suggested monitoring and consent conditions should this application be granted;<br />
and,<br />
d) A summary of matters that I consider to be outstanding.<br />
8. Technical material relating to surface water hydrology, in particular the significance of the<br />
natural stream flow alteration as a result of the activity, have been reviewed by Thompson<br />
(2013). The review of surface water hydrology by Thompson (2013) has been used to help<br />
inform my understanding of some of the potential effects of this proposal.<br />
1287853-V2 PAGE 2 OF 14
Findings of review<br />
Adequacy of information and assessment of effects<br />
Characterisation of water quality and ecology<br />
9. The AEE produced by EAM characterises the ecological values of the unnamed tributary<br />
of the Wakamoekau Creek by making general observations of the area to be affected,<br />
describing stream habitat, undertaking surveys of the aquatic fauna and flora, and collecting<br />
one-off water quality samples. Where appropriate, aspects of these assessments are<br />
discussed further below.<br />
Steam habitat assessment<br />
10. The AEE provides good written descriptions of the stream habitat at three locations; at the<br />
dam site and also above and below the dam site. The descriptions of the habitat are<br />
consistent with my observations from when I visited the site. The stream reaches within the<br />
dam foot print can be considered to be moderately degraded in terms of aquatic habitat. In<br />
contrast, some of the reaches above the dam site have moderate to good habitat (eg, a<br />
variety of instream habitats such as pools, riffles and runs and some riparian planting).<br />
Water quality sampling<br />
11. Water quality sampling was limited to the collection of one-off samples. While analysis of<br />
one-off samples can be useful it is not appropriate to draw firm conclusions based on one<br />
set of samples (ie, a larger dataset is required given the variability in water quality data) as<br />
has been done in the AEE. Furthermore, Table 2 of the AEE that presents the water quality<br />
data contains an error as total Kjeldahl nitrogen, nitrite-nitrate nitrogen and total nitrogen<br />
concentrations are all presented as being 1,000 µg/L (total nitrogen should equal the sum<br />
of total Kjeldahl nitrogen and nitrite-nitrate nitrogen).<br />
12. The AEE concludes that the “existing water quality is poor and typical of an unprotected<br />
lowland stream”. While I don’t strongly disagree with this statement, based on the limited<br />
sampling, it would be more appropriate to conclude that the water quality is likely to be of<br />
low to moderate quality (rather than poor) and probably fairly typical of other small streams<br />
running through low intensity pastoral land use that has some stock access. Overall, while<br />
not ideal, the water quality of the unnamed tributary is probably quite suitable for providing<br />
habitat for a range of aquatic fauna.<br />
<strong>Aquatic</strong> fauna surveys<br />
13. The AEE states that macroinvertebrate life is “...generally poor but good numbers of koura<br />
were found throughout the catchment with the exception of the open pasture reaches”.<br />
However, no robust survey of the macroinvertebrate community following standardised<br />
national sampling techniques (eg, Stark et al. 2001) was undertaken. Thus the conclusion<br />
that the macroinvertebrate fauna “was very poor and typical of a degraded eutrophic water<br />
body” must be interpreted with caution as this conclusion was formed based on “basic<br />
searches”.<br />
1287853-V2 PAGE 3 OF 14
14. Given the scale of the dam and the potential effects it would have been appropriate to<br />
undertake a macroinvertebrate survey at several locations (eg, dam site and upstream and<br />
downstream of the dam site) following standardised national protocols. These results would<br />
have been useful for providing some information on the macroinvertebrate community<br />
condition for the different stream reaches that contain different habitat quality (eg, dam site<br />
vs. upstream), supplemented the limited water quality results (as macroinvertebrate<br />
community condition responds to water quality as well as other factors such as habitat) and<br />
been useful for discussing the potential effects of the application. A better understanding of<br />
the macroinvertebrate community could also be factored into the design of the diversion<br />
channels and used to set ‘mitigation targets’ to which this community must meet in the new<br />
diversion channels (to show that mitigation has been successful).<br />
15. The fish survey undertaken to inform the AEE involved a significant amount of<br />
spotlighting (four hours) and some limited trapping and netting. The trapping and netting<br />
effort would generally be considered very low (see Joy et al. 2013) but the high spotlighting<br />
effort compensates for this. Longfin eel and common bully were recorded during these<br />
surveys, both of which were considered common. Koura (freshwater crayfish) and several<br />
congregations of Kakahi (freshwater mussels) were also recorded. The information from<br />
these surveys was supplemented by using NIWA’s national freshwater fish database and<br />
interpreting the fish survey records for the Waipoua River to assess if additional species<br />
may be present.<br />
16. While the fish survey represents a reasonable level of effort, given the potential effects of<br />
the application, the fish survey should also have included backpack electric fishing.<br />
Backpack electric fishing is a survey method that allows for the assessment of riffle-type<br />
habitats that cannot be adequately assessed using spotlighting and nets/traps. This is<br />
important given that riffle dwelling species, such as the threatened dwarf galaxias, have<br />
been recorded within the Waipoua River catchment and a key habitat type for this species is<br />
smaller streams located in foothill catchments (McDowall 2000). Furthermore, the more<br />
fish survey methods used, the more likely that the entire fish community present within a<br />
reach will be sampled (eg, due to biases/limitations associated with different sampling<br />
methods, Joy et al. 2013).<br />
17. A backpack electric fishing survey of the unnamed tributary upstream of the dam site was<br />
undertaken by GWRC (November 2011). This survey focused on assessing all habitat types<br />
available (riffles, runs and pools) and found good numbers of both longfin eel (a good<br />
range of sizes including elvers) and Cran’s bully. Koura (freshwater crayfish) were also<br />
recorded in good numbers. Cran’s bully was not recorded during the EAM surveys and<br />
common bully was not recorded during the GWRC survey.<br />
18. Overall the diversity of the fish community is low, but fairly typical of a small pastoral<br />
stream that is located a relatively long way inland from the coast. And the fish survey<br />
results are generally consistent with predictive models (eg, the Freshwater Environments of<br />
New Zealand or FENZ predictive model indicates that this stream is mainly going to<br />
provide habitat for longfin eel). The good numbers of longfin eel are also an indication that<br />
1287853-V2 PAGE 4 OF 14
habitat and water quality remain in at least a moderate condition as this species is generally<br />
absent or in low abundance in highly degraded pastoral streams.<br />
19. EAM correctly identify that longfin eel are classified by the Department of Conservation<br />
(Allibone et al. 2010) as a threatened species (at risk; declining) but in their overall<br />
conclusion they neglect to mention that both koura and kakahi are also classified as<br />
declining (Hitchmough et al. 2007). The presence of kakahi is somewhat unusual and I’m<br />
not aware of any other records of kakahi from this area or nearby rivers/streams draining<br />
the Tararua Range. Most populations are associated with catchments in the eastern<br />
Wairarapa or lower Ruamahanga. In addition to the conservation interest in these three<br />
species, all also have significant cultural value (mahinga kai species).<br />
Wakamoekau Creek and Waipoua River<br />
20. The focus of the EAM’s AEE was to characterise the ecological values of the unnamed<br />
tributary. The AEE does not attempt to characterise the ecological values of the<br />
Wakamoekau Stream or the Waipoua River. Some recognition, generally in regards to<br />
policies in GWRC’s Freshwater Plan (RFP) and Regional Policy Statement (RPS), of the<br />
ecological and recreational values is provided in Cheal (2013).<br />
21. Given the potential effects of the proposed activity, it is a significant gap to not characterise<br />
the ecological values of the Wakamoekau Stream and the Waipoua River. At minimum, a<br />
desktop review of relevant ecological information should have been undertaken, especially<br />
given the known values of these systems. A site visit, and potentially additional surveys of<br />
the ecology of the Wakamoekau Creek, would also have been appropriate.<br />
22. Known values and/or issues associated with these water bodies that should have been<br />
investigated and discussed include, but should not necessarily be limited to:<br />
a) Trout habitat: The Wakamoekau Stream and the Waipoua River are both listed in<br />
GWRC’s RFP as water bodies with important trout habitat (including spawning<br />
areas).<br />
b) Indigenous fish values: The Waipoua River (including its tributaries) is listed in<br />
the RPS as a significant indigenous ecosystem: habitat for threatened indigenous<br />
fish species.<br />
c) Recreational values and benthic cyanobacteria: The Waipoua River has high<br />
recreational values (swimming in the reaches that flow through Masterton) but it is<br />
also prone to blooms of potentially toxic benthic cyanobacteria (eg, Greenfield et<br />
al. 2012). Given that this application may result in changes in the flow regime of<br />
the Waipoua, and that this may influence periphyton/cyanobacteria growth, some<br />
discussion of this issue is warranted.<br />
1287853-V2 PAGE 5 OF 14
Effects assessment<br />
23. The AEE documents some of the potential effects from this proposal but does not provide a<br />
comprehensive discussion around all of these effects. From my understanding of the<br />
application the range of potential effects from the proposed activity are as follows:<br />
a) A significant length of stream will be lost/drowned by dam;<br />
b) A significant length of stream will be diverted to bypass the dam;<br />
c) At times flows in the unnamed tributary downstream of the dam will be reduced<br />
and flow variability, including flushing flows, will be affected;<br />
d) At times flows in the Wakamoekau Creek and Waipoua River will be reduced and<br />
flow variability, including flushing flows, will be affected (albeit not to the extent<br />
experienced by the unnamed tributary);<br />
e) Fish passage to habitat upstream of the dam may be inhibited; and,<br />
f) A discharge of poorer water quality from the dam could occur to the unnamed<br />
tributary.<br />
24. Where appropriate, these effects are discussed in more detail in the sections below. Having<br />
a clear idea of the potential effects is a necessary step in determining appropriate mitigation<br />
measures.<br />
Stream length lost and/or diverted<br />
25. Based on the application, a significant length of stream will be drowned by the dam<br />
(1.5km). Of this 1.5km, approximately 900m will be replaced by a diversion channel;<br />
which are referred to in the application as the low flow diversion channel (430m) and the<br />
dam overflow channel/realigned stream (~430m). This results in a shortfall of around 600m<br />
of stream length that will be lost under this proposal (although note that total length of the<br />
diversion channel requires further clarification).<br />
26. The effects of the proposed diversions and the loss of stream habitat are not addressed in<br />
any detail in the AEE or Cheal (2013) and are largely written off as negligible because the<br />
stream to be lost is “very limited and degraded”. The loss of 600m of stream length, even<br />
of “degraded” habitat, is still a significant amount of stream and this will require mitigation.<br />
27. No information was provided on how the stream diversion will be constructed. The stream<br />
diversion will need to be designed by a suitability qualified and experienced freshwater<br />
ecologist and to a high standard (ie, improve the quality of the habitat over the existing<br />
stream habitat) if it is going to be offered as mitigation. While riparian planting of the<br />
diversion channel is proposed as part of the current mitigation package, the diversion<br />
design needs to go further and include the design of instream morphological habitat (eg,<br />
pools, runs, riffles, etc.).<br />
1287853-V2 PAGE 6 OF 14
28. From aerial photographs in GIS it also appears that the ‘dam overflow channel/realigned<br />
stream’ falls at least partly within the catchment of another small catchment south of the<br />
main unnamed catchment. Clarification is required as to whether this is the case or not; if it<br />
is, additional information on the effects on this catchment may be required.<br />
Reduced flow, flow variability and magnitude of flushing flows<br />
29. The application has two proposed scheme operations, ‘summer’ (November to April) and<br />
‘winter’ (May to October). Under the summer operation, all natural flow in the unnamed<br />
tributary will be diverted around the dam (ie, left in the stream) unless flow exceeds 25 L/s.<br />
If the tributary is flowing greater than 25 L/s, harvesting of water into the dam will occur<br />
(ie, in summer, a residual minimum flow of whichever is the lowest of the natural stream<br />
flow or 25 L/s will be maintained in the diversion channel and unnamed tributary). During<br />
the months May to October (inclusive), water is proposed to be harvested at any time that<br />
flow in the Waipoua River exceeds 1,000 L/s, including at times when the natural flow in<br />
the un-named tributary is less than 25 L/s (ie, in winter, the 25 L/s residual flow will not<br />
necessarily be maintained).<br />
30. Regardless of the operation (summer and winter), when water is harvested (diverted) into<br />
the dam there will be less water volume flowing through the diversion channel and into the<br />
unnamed tributary below the dam. Additionally, harvesting will impact on the variability of<br />
flow experienced downstream, including flushing flows (as water is harvested under these<br />
higher flows). These effects will be most severe in the unnamed tributary but will also be<br />
exhibited, in decreasing amounts, in the Wakamoekau Creek and the Waipoua River. These<br />
effects have not been well documented in the AEE although some are briefly discussed in<br />
Cheal (2013).<br />
31. Potential ecological effects from the harvesting (ie, reduced flow and reduced flow<br />
variability) that should have been discussed in regards to the ecological values of the<br />
unnamed tributary, the Wakamoekau Creek and the Waipoua River include:<br />
a) A reduction in aquatic habitat available;<br />
b) A reduction in the dilution of contaminants (eg, nutrients);<br />
c) An increase in water temperature and subsequent decrease in concentrations of<br />
dissolved oxygen;<br />
d) A loss of connectivity with marginal (edge) stream habitat and the ‘ecosystem<br />
services’ these areas provide;<br />
e) An increase in periphyton and macrophyte growths due to increased flow stability;<br />
f) A reduction in flushing/removal of periphyton and macrophyte growths; and,<br />
g) A reduction in flushing/removal of streambed sediment.<br />
1287853-V2 PAGE 7 OF 14
32. In determining the extent of the ecological effects listed above, it is important that the<br />
hydrological effects are fully characterised as these are necessary to link with the ecological<br />
values (and subsequently determine effects). The review undertaken by Thompson (2013)<br />
highlights some deficiencies in the hydrological information provided to date, especially in<br />
regards to the effects (frequency and magnitude) of the harvesting on base flows and<br />
flushing flows.<br />
33. Given that an accurate understanding of the hydrological effects of this proposal is critical<br />
in determining the potential ecological effects, I support the recommendation by Thompson<br />
(2013) for further hydrological assessment. In lieu of this additional information, general<br />
comments on the potential effects of the harvest proposal for each of the three water bodies<br />
that require further discussion by the applicant are outlined below.<br />
Unnamed tributary<br />
34. Approximately 1.5km of the unnamed tributary downstream of the dam (this approximate<br />
length includes the diversion channel) will, at times, be significantly affected by reduced<br />
flow and reduced flow variability. For example, during the winter operation when<br />
harvesting is occurring, the volume of flow diverted into the dam is quite considerable (eg,<br />
approximately 70%, see Thompson (2013) for details). There will also be no minimum<br />
flow maintained in the unnamed tributary during the winter harvest period and under some<br />
conditions it is possible that the flows will drop to quite low levels when compared to<br />
winter base flows.<br />
35. Given that 1.5km is a significant length of stream, and that the stream has at least<br />
‘moderate’ ecological values, further assessment specific to the effects (as outlined above)<br />
of this reduced flow and reduced flow variability on the ecological values of the unnamed<br />
tributary is required. This assessment of ecological effects needs to be based on clarified<br />
hydrological effects (reduced flow and reduced flow variability), such as how often flow<br />
will be affected, to what extent, and how this will vary under the different operation<br />
regimes and ‘natural’ flows upstream of the dam. The details of the hydrological analysis<br />
required are fully outlined in Thompson (2013).<br />
Wakamoekau Creek<br />
36. Approximately 4km of the Wakamoekau Creek between the confluences of the unnamed<br />
tributary and the Waipoua River will be affected by reduced flows and flow variability.<br />
Cheal (2013) indicate that harvesting is unlikely to reduce flows in the Wakamoekau by<br />
more than 12% and they conclude that this will be of minimal impact on the ecosystem.<br />
However, neither Cheal (2013) nor EAM’s AEE have characterised the ecological values of<br />
the Wakamoekau Creek or how these values are linked (or not) with flow. Characterisation<br />
of the ecological values of the Wakamoekau Creek should occur before a conclusion is<br />
made on the ecological effects of the flow harvesting operation.<br />
1287853-V2 PAGE 8 OF 14
Waipoua River<br />
37. While the overall proportion of flow in the Waipoua River contributed by the unnamed<br />
tributary is considered low (
help determine some of the potential effects from this proposal and may also identify<br />
potential mitigation options.<br />
44. The information required needs to include how the stream will be dealt with during<br />
construction. Ideally the stream diversion should occur first and be in operation before the<br />
construction of the dam to minimise on-going disturbance of the stream. The construction<br />
plan will also need to clearly outline mitigation steps, such as the design of the diversion<br />
channel and how aquatic fauna and flora will be translocated from the existing stream to the<br />
new diversion.<br />
Consideration of the effects on high value aquatic fauna<br />
45. A specific effects assessment regarding the high faunal value species present is lacking. In<br />
terms of all the effects above, further assessment is required that focuses on the ‘high value’<br />
fauna present in these water bodies, such as the longfin eel, kakahi and koura – all of which<br />
have conservation and important cultural values (mahinga kai species). For example, how<br />
will kakahi populations be affected by the changes in flow regime that will occur under this<br />
proposal?<br />
46. While I acknowledge that the unnamed tributary does not appear to provide good trout<br />
habitat, the effects on trout (including spawning areas and spawning migrations) still need<br />
to be discussed in regards to the value of the Wakamoekau Creek and the Waipoua River.<br />
Mitigation<br />
47. The mitigation is proposed as an overall package in Cheal (2013) and consists of fencing<br />
and riparian planting of the diversion channel and the reach downstream of the dam to<br />
Matahiwi Road, and also (just) fencing upstream of the dam.<br />
48. To better assess the appropriateness of this overall package, a more transparent mitigation<br />
plan is required. This needs to include actual stream lengths of planting and fencing, along<br />
with the specific affects being mitigated. For example, the AEE states that “to counter the<br />
loss of flow from the tributary it is recommended that riparian protection be<br />
undertaken….”. However, there is no mention of what mitigation is being offered for the<br />
approximately 600m of stream that will be lost/drowned. It’s worth noting that robust<br />
methods are available for calculating appropriate mitigation when a length of stream is lost<br />
(eg, SEV) and that these have not been used. The mitigation plan also needs to demonstrate<br />
how the type of mitigation was calculated/derived and why it is suitable in offsetting the<br />
effects, or aspects of, the proposal.<br />
49. As mentioned previously, the construction of the diversion channel to enhance stream<br />
habitat, along with how the construction is staged, will be key parts of the mitigation<br />
package that require further detail.<br />
50. Based on the information supplied, my current opinion is that the mitigation proposed in<br />
Cheal (2013) is not sufficient (given the cumulative effects of reduced flow and reduced<br />
flow variability, diversions and stream length lost, as well as potential downstream effects).<br />
1287853-V2 PAGE 10 OF 14
Additional mitigation options should be explored such as extending the riparian planting<br />
and fencing (eg, downstream of Matahiwi Road if suitable and/or on additional streams<br />
located on the property) and remediation of existing fish passage issues (eg, the structure<br />
that creates a drop-off at Matahiwi Road bridge).<br />
51. The riparian guidelines (MfE’s (2001) Managing Water Ways on Farms) referred to by<br />
Cheal (2013) provide good guidance on how to undertake riparian restoration. However,<br />
further detail is required on how exactly this riparian planting is undertaken, eg, width of<br />
planting (should be a minimum of at least 10m on each side of the stream but ideally 20m),<br />
spacing of plants, weed control regime, etc. This detail could be specified in either a<br />
consent condition or riparian planting plan (to agreed specification with GWRC) required<br />
by a condition, or provided as part of an updated mitigation plan.<br />
52. Man-made dams are frequently subject to the introduction of invasive aquatic plant and fish<br />
species; they can act as ‘strongholds’ for these species and aid their spread throughout the<br />
catchment. It would also be beneficial for the mitigation plan to outline a strategy that will<br />
minimise the introduction (as far as practicable) of exotic plants and animals to the dam.<br />
Proposed monitoring and consent conditions should this application be granted<br />
Monitoring<br />
53. There appears to be no monitoring of ecological values or effects proposed in Cheal (2013).<br />
In the AEE, EAM propose annual ecological monitoring but no specific detail is provided<br />
of what this monitoring should be. At minimum, if this application is granted, I would<br />
expect the following to occur:<br />
a) The diversion channel is monitored/checked by a suitably qualified and<br />
experienced freshwater ecologist prior to flow being diverted into it, and<br />
subsequent checks one year, and then three years later. This monitoring is to<br />
ensure that the channel is functioning to the design specifications and achieving<br />
appropriate mitigation of the effects of the proposed activity (ie, enhancing<br />
instream habitat). Reporting of this monitoring should include any<br />
recommendations for modifications to the diversion channel, if required, and<br />
recommend whether further monitoring of the diversion channel is warranted.<br />
b) Flows at the top and the bottom of the diversion channel are monitored for an<br />
initial period to ensure that no flow is lost through the new section of stream.<br />
c) Monitoring of riparian restoration plantings at appropriate intervals to ensure that<br />
mitigation targets are being met.<br />
d) Ecological surveys undertaken three and ten years after construction is complete<br />
that assess stream habitat and aquatic fauna condition, with a particular focus on<br />
longfin eel, koura and kakahi. Recommendations for additional mitigation<br />
options, if required, and further monitoring requirements should also be part of this<br />
assessment.<br />
1287853-V2 PAGE 11 OF 14
Consent conditions<br />
54. If this application is granted I would expect the matters outlined below to be<br />
incorporated/addressed within consent conditions:<br />
a) All monitoring, as outlined above (paragraph 53);<br />
b) The design of the diversion channel is undertaken by a suitably qualified and<br />
experienced freshwater ecologist and the design demonstrates how stream habitat<br />
will be enhanced (to the satisfaction of GWRC);<br />
c) Appropriate detail on the riparian planting is provided to ensure that it provides<br />
sufficient mitigation;<br />
d) Appropriate mitigation targets are specified to ensure that mitigation occurs to an<br />
agreed standard and actions to be undertaken if these targets are not achieved;<br />
e) An appropriate flow through the diversion channel for the winter harvest period is<br />
set and maintained when flow is being harvested;<br />
f) No flow is lost through the diversion channel;<br />
g) Fish passage is maintained at all times past (upstream and downstream) the weir<br />
structure used to harvest flow and, as far as practicable, fish passage is maintained<br />
in and out of the dam;<br />
h) Discharge from the dam to the unnamed tributary does not occur (as far as<br />
practicable); and,<br />
i) As per the recommendation in Thompson (2013), a condition that stops harvesting<br />
from occurring if GWRC deem that a flushing flow is required in the Waipoua<br />
River.<br />
Overall comments and matters still outstanding<br />
55. The AEE produced by EAM generally characterises the ecological values of the unnamed<br />
tributary and I agree that this stream can probably be classified as, overall, having<br />
‘moderate’ ecological values. Some additional assessments, such as macroinvertebrate<br />
surveys following standardised national methods, would have been useful in providing<br />
further evidence of this moderate classification. However, the presence of good numbers of<br />
longfin eel, koura and kakahi (all of which are classified as threatened by DoC) and also the<br />
high cultural values (mahinga kai species), place this stream at the high end of the<br />
‘moderate value streams’.<br />
1287853-V2 PAGE 12 OF 14
Matters still outstanding<br />
56. While the ecological values of the unnamed tributary are generally well established in the<br />
AEE, the values of the other affected water bodies are not. Furthermore, linkages between<br />
specific effects and specific instream values are generally lacking and the overall mitigation<br />
package does not clearly indicate which effects the mitigation is addressing. The main<br />
deficiencies with this application that require further information and discussion before this<br />
application can be progressed are outlined below.<br />
Assessment of effects<br />
57. The likely effects of the reduction in base flows and flow variability (including flushing<br />
flows) need to be linked to the specific instream values (including high value species such<br />
as longfin eel, koura and kakahi) of the unnamed tributary. This should be undertaken using<br />
hydrological statistics that summarise the effects of the harvesting on the flow regime as<br />
specified in Thompson (2013).<br />
58. The instream values (ecological and recreational) of the water bodies downstream of the<br />
unnamed tributary (Wakamoekau Creek and Waipoua River) need characterising and<br />
linking of the likely effects of the reduction in base flows and flow variability (including<br />
flushing flows) to the values specific to these water bodies is needed. This should be<br />
undertaken using hydrological statistics that summarise the effects of the harvesting on the<br />
flow regime as specified in Thompson (2013).<br />
Mitigation<br />
59. A clear and transparent mitigation plan is required that sets out the potential effects of the<br />
applicant’s proposed activities and what is being proposed to mitigate these effects. This<br />
plan needs to relate specific mitigation actions proposed for each effect (eg, stream lost,<br />
stream diverted, reduction in flows and reduction in flow variability). This plan should<br />
include an accurate breakdown of the stream lengths involved (affected and mitigated),<br />
construction details where these are pertinent to the mitigation package (eg, construction of<br />
instream habitat within the diversion channel, aquatic fauna translocation, etc.) and the<br />
finer details of fencing and riparian planting that will occur (including on-going<br />
management). The plan also needs to demonstrate how the type of mitigation was<br />
calculated/derived and why it is suitable in offsetting the effects of the proposed activities.<br />
References<br />
Allibone R, David B, Hitchmough R, Jellyman D, Ling N, Ravenscroft P and Waters J. 2010.<br />
Conservation status of New Zealand freshwater fish, 2009. New Zealand Journal of Marine and<br />
Freshwater Research, 44: 1–17.<br />
<strong>Greater</strong> Wellington Regional Council. 2013. Regional Policy Statement for the Wellington region.<br />
Publication No. GW/EP-G-13/21, Wellington.<br />
1287853-V2 PAGE 13 OF 14
Greenfield S, Ryan A and Milne J. 2012. Recreational water quality in the Wellington region: State<br />
and trends. <strong>Greater</strong> Wellington Regional Council, GW/EMI-T-12/142, Wellington.<br />
Hitchmough R, Bull L and Cromarty P. 2007. New Zealand threat classification system lists, 2005.<br />
Department of Conservation, Wellington.<br />
Joy M, David B and Lake M. 2013. New Zealand freshwater fish sampling protocols: Part 1,<br />
wadeable rivers and streams. Massey University, Palmerston North.<br />
McDowall RM. 2000. The Reed field guide to New Zealand freshwater fishes. Reed Books Ltd,<br />
Auckland.<br />
Stark JD, Boothroyd IKG, Harding JS, Maxted JR and Scarsbrook MR. 2001. Protocols for<br />
sampling macroinvertebrates in wadeable streams. New Zealand Macroinvertebrate Working Group<br />
Report No. 1. Prepared for the Ministry for the Environment, Sustainable Management Fund Project<br />
No. 5103.<br />
Wellington Regional Council. 1999. Regional Freshwater Plan for the Wellington region.<br />
Wellington Regional Council, Publication No. WRC/RP-G-99/31, Wellington.<br />
Alton Perrie<br />
Environmental Scientist<br />
Environmental Science Department<br />
DD: 06 826 1545<br />
alton.perrie@gw.govt.nz<br />
1287853-V2 PAGE 14 OF 14