Proposed review of Whangamarino river weir Resource Consent
Review of resource consent
890227
issued
to
Minister of
Conservation
and
Auckland/Waikato
Fish & Game Council
It has been proposed by the WRC that the above resource consent is to be reviewed and below is my summary of the facts surrounding the decision to review this consent.
Condition (h) of resource
consent 890227 states:
“The Waikato Regional
Council may give notice pursuant to section 128 of the
Resource Management Act 1991, of its intention to
review any or all of the conditions of this
consent two years from the date of completion of
reconstruction (the two years shall
include the
collection of data from two summer periods) and at
five yearly intervals thereafter.
Purpose of
Review:
“to deal with any adverse effect on
the environment which may arise from the exercise of the
consent…”
“considering the effect of the weir on
both ground and surface water levels on adjacent private
land and ecological values in the wetlands”
In
summary, any condition may be reviewed to
deal with any adverse effects on the environment.
Further, the condition sets out that particular focus
should be given to effects on ground and surface water on
adjacent private land and ecological values in the
wetland.
Anticipated Effects
The
decision makers when looking at this consent, considered
that there were uncertainties on the effects of the weir and
it was anticipated that monitoring would determine these
effects. The decision makers expected that there would be
no effects on the flood scheme, provided that the
flood scheme operated as designed.
The effects on
flora and fauna were to be monitored and pests managed. A
review condition was provided for in case adverse effects
would be greater than expected.
Actual
Effects
Monitoring Information
A consent compliance audit report issued in
August 2016 notes that the monitoring reports as required by
consent conditions have not been adequately provided. The
monitoring and reporting frequency has not been complied
with and the reports do not address all the matters required
by the conditions.
Also, an assessment of effects
is lacking or insufficient in respect to many of
the matters. Also, the consent holders or their
representatives have assessed that some of the
required monitoring can either not be physically
undertaken or the monitoring information will not
adequately provide the information as intended by the
conditions.
In summary, the monitoring information provided by the consent holders indicates that sedimentation is occurring in waterways upstream of the weir. The cause of sedimentation is due to a range of potential factors including the presence of the weir. Sedimentation resulted in an increase in water levels which may be greater than the consented level. This trend continues. Groundwater levels are linked to surface water levels.
Murray Mulholland, WRC Senior Engineer,
commented on the 2016 Jacobs interim report as
follows:
“...The
conclusion is correct in stating that there a number of
different factors which impact on siltation. These include
catchment sediment inflows, Waikato River levels, and the
Weir. It is very difficult to disaggregate the effects of
all these influences, but it is reasonable to conclude that
the weir does increase siltation to some extent because it
reduces velocities in the river and thus reduces sediment
loads.”
“…the report does not discuss any
impacts of the weir on private land in respect to
either groundwater or surface water. Surface water effects
are identified as a gap to be addressed in the final
monitoring report (but not groundwater).”
Pest
Management
DOC report 2014 (WRC doc#3442058)
Consent conditions do not require monitoring of
changes in pest numbers and/or extent.
Rather, the
condition requires ongoing reviews of the methods for
controlling pests such as koi carp, feral cats, stoats,
opossums, rats and willows.
Pest Fish
While the Department of Conservation
considers the high biomass of pest fish (particularly
koi carp) in the Whangamarino is likely to be having
negative ecological impacts (Lake et al. 2011), there are
Currently no effective methods available for control of pest
fish species in Iarge systems such as Whangamarino. The
Department will continue to review available methods
for pest fish management and will consider undertaking
pest fish control should adequate, cost effective and
environmentally sensitive methods become
available.”
Noxious pests
“DOC
takes an adaptive management approach to predator
control at the wetland. A range of biodiversity
inventory surveys and monitoring programmes have also been
established at Whangmarino to assess changes in the
abundance of pest species.”
Currently there is
no pest fish management in the
wetland.”
In summary, the
monitoring information indicates that pest management and
regular reviews of the methods for controlling pests is
undertaken.
There are in place strategies for control
of:
Weeds
Deer
Pigs
Mustelids
Feral
Cats
Rodents
But the worst
invasive pests Koi Carp & Possums have no
strategies in place to manage and control them.
Until now Possums have not been seen as a priority as they were thought to have little impact on the wetland and Koi Carp, even though they are acknowledged by DOC as a noxious fish, are ignored on the basis that even though they are likely to be having negative ecological impacts there are currently no effective methods available for control of pest fish species in Iarge systems such as Whangamarino.
Flooding / Flood Drainage Scheme
The WRC Integrated Catchment Management (ICM)
Directorate administers the flood control schemes. Ghassan
Basheer, Principal Technical Advisor to ICM, reviewed
the 2014 monitoring report and made the following
comments (WRC document #10082989):
Sedimentation
“The sedimentation
issue was raised during the consent hearing, because it was
expected to become a major issue. That is why surveys and
monitoring was required. Our opinion is that the
accelerated sedimentation in the river is artificial
and substantially due to the weir. In its natural
state, all sediment from the catchments upstream was moving
downstream into the Waikato. Rate of sediment build up was
very small compared to what it is now following the weir.”
Water Level
“…When the
weir consent was applied for, an assessment was
carried out by RCS [ICM] to establish the maximum
height to which the average wetland water level
could be raised without compromising the storage capacity
within the wetland and ultimately compromising the scheme
stopbanks. That level was RL 3.4 m.”
I note that the Hearings Committee in 1996 stated that “The weir is designed to maintain water levels in the wetland at an average height of 3.4 metres”.
Mr Basheer described the average water level: “The basis for measuring the average wetland level in our report was a midpoint between Falls Road and Ropeway...”
Mr
Basheer then outlines ICM’s assessment of effects: “Our
assessment of the average water level “average of two
gauges” is RL 3.57 m which is significantly higher than RL
3.4 m. In our opinion this will have significant
implications on the flood storage capacity.
(Note: this
assessment was based on analysing the average water levels
for the period 2001
following the weir reconstruction
to 2014 between the Falls Road Recorder and Ropeway
Recorder, which represent the upper and lower ends of the
wetland).
Within the first 2 years following the weir structure upgrade in May 2000 we did not detect / experience significant surface water, or underground water issues and complaints. However, we have since noticed that some of the unprotected farmland to be inundated for long periods of time. We have recently had a piping failure within the Parish Polder flood protected compartment, due to high groundwater table. We have also received some 6 years ago two complaints about surface water flooding.”
In summary:
“The average water level of the wetland is defined as the average level between the two recorders (e.g. Falls Road and Ropeway). The minimum average over the last 13 years is RL 3.57 m (e.g. 0.17 m above what RCS [ICM] agreed to during the original consents hearing). We are having problems now with surface flooding and ground water levels in a number of areas.”
Mr
Basheer made also the following comments in respect to
effects on fish:
Fish
“The
upstream end of the wetland is currently drowned below RL
3.00 m all year around. During the summer, especially
when there is no flow from the catchment and Lake
Waikare, the upstream part is stagnant and dissolved oxygen
levels are very low affecting fish life. No one seems to
assess the severity of this problem.”
Koi
Carp:
In relation to Koi Carp there has been no
monitoring done as to the effects that the Koi are having on
the native species even though it is known that due to their
feeding methods they will predate on the native species of
both flora and fauna in the waterways.
The Koi Carp are
able to exist in very degraded water quality and their
feeding methods cause substantial degradation of the
waterways.
With the increase in water levels within the wetland as a result of the installation of the weir there has been an increase in the habitat available for the breeding of Koi Carp. The associated increased numbers of Koi Carp have had a substantial effect on the erosion of the banks of the waterways and due to this increased level of erosion a subsequent rise in the levels of sedimentation within the wetland.
This has to some extent been proven as a credible scenario by the results of the water quality investigations and report done recently by DR Doug Edmeades and Mr Fred Phillips which has shown that the decrease in water quality within the wetland is mainly due to a rise in the levels of Phosphorous and Sediment, with Nitrate discharge being within required regulatory limits.
The elevated levels of P within the wetland water are in my opinion directly related to the levels of sediment in the waters and the levels of sediment are hugely affected by the high numbers of Koi Carp breeding and feeding within the wetland.
To say that we can’t do anything about the high biomass of pest fish (particularly koi carp) in the Whangamarino even though it is likely to be having negative ecological impacts (Lake et al. 2011), because there are Currently no effective methods available for control of pest fish species in Iarge systems such as Whangamarino is in my opinion just a cop out.
The Department of Conservation states that it will continue to review available methods for pest fish management and will consider undertaking pest fish control should adequate, cost effective and environmentally sensitive methods become available.”
So in effect even though they have plenty of evidence relating to the detrimental effects of Koi Carp (they declare them to be a noxious invasive species on their website) they will turn a blind eye to the whole issue mainly due to the costs of eradication or control and reduction of numbers.
Taking into account the information available on the DOC website in relation to Koi Carp, it is plain to see that with the highly successful breeding rates of the Koi Carp combined with the lack of any natural predators in the NZ situation, and their ability to exist in highly degraded water ways, the only thing that will naturally stop the expansion of numbers (and the subsequent eradication of native flora and fauna) of Koi Carp will be their own depredations of their food sources due to their hugely increased biomass.
In my opinion and in light of the above information, the do nothing attitude because they say there is no effective methods for control, is equivalent to that old saying about twiddling their thumbs while Rome Burned.
Unless we do something now we will not have any native flora or fauna left to protect in the near future due to the depredations of Koi Carp.
Andy
Loader
Co-Chairman
P.L.U.G.