WAIKAREMOANA POWER SCHEME

Page created by Jimmy Sparks
 
CONTINUE READING
WAIKAREMOANA POWER SCHEME
POWER SCHEME
                                               WAIKAREMOANA

ENVIRONMENTAL REPORT // 01.07.12 // 30.06.13
WAIKAREMOANA POWER SCHEME
13   This report provides a summary of key environmental outcomes arising out
     of the process to renew resource consents for the ongoing operation of the
     Waikaremoana Power Scheme.
     The process to renew resource consents was lengthy and complicated, with
     a vast amount of technical information collected. It is not the intention of
     this report to reproduce or replicate this information in any way, rather it
     summarises the key outcomes for the operating period 1 July 2012 to 30 June
     2013 (hereafter referred to as ‘the reporting period’).
     The report also only provides a summary of key result areas. There are a
     number of technical reports, research programmes, environmental initiatives
     and agreements that have fed into this report. As stated above, it is not the
     intention of this report to reproduce or replicate this information, rather to
     provide a summary of it. Genesis Energy is happy to provide further details or
     technical reports or discuss matters directly with interested parties.
WAIKAREMOANA POWER SCHEME
HIGHLIGHTS
                                                                       1 July 2012–30 June 2013
02   01      INTRODUCTION
02   1.1     Document Overview                                         Maintenance Consents In February 2013, scheme-wide
02   1.2     Resource Consent Process Overview                         resource consents to undertake various routine maintenance
02   1.3     How to use this document                                  activities at the Waikaremoana Power Scheme were granted
02   1.4     Genesis Energy’s Approach                                 by Hawkes Bay Regional Council (HBRC). Prior to the scheme-
             to Environmental Management                               wide maintenance consents, resource consents for routine
02   1.4.1   Genesis Energy’s Values                                   maintenance activities were applied for on an ad-hoc basis
02   1.4.2   Environmental Management System                           which involved frequent repetition. The new consents provide
03   1.4.3   Resource Consents Management System                       an efficient mechanism to undertake routine maintenance
03   1.4.4   Hydrology                                                 activities, whilst effectively managing the effects of the activities
03   1.5     Feedback                                                  on the environment (see Section 5.1.1 for details).
04 02        WAIKAREMOANA POWER SCHEME
                                                                       Waikareiti Biodiversity Restoration Project Genesis Energy
05 2.1       Operating the Waikaremoana Power Scheme
                                                                       entered into a three year Waikareiti Biodiversity Restoration
05 2.2       Climate and Power Generation
                                                                       Project Sponsorship Agreement with the Department of
06   03      LAKE WAIKAREMOANA                                         Conservation (DOC) in February 2012.  The project’s vision is
07   3.1     Hydrology                                                 that “The Waikareiti landscape is pest free and native species
08   3.1.1   Level Trends at Lake Waikaremoana                         thrive in abundance”.  DOC field staff and tangata whenua
08   3.2     Ecosystems and Water Quality                              established predator trapping infra-structure around the
08   3.2.1   Terrestrial Vegetation                                    lakeshore this reporting period ready for removal of pests from
08   3.2.2   Aquatic Vegetation                                        all six islands on Lake Waikareiti, using hand-spread toxins
09   3.2.3   Trout Monitoring                                          (see Section 6.3 for details).
09   3.2.4   Ecological Restoration Programme
10   3.3     Sediment (Erosion, Transport and Deposition)              Waikaremoana Lagarosiphon Incursion In February 2012, a
10   3.3.1   Event-Driven Monitoring                                   DOC contractor located Lagarosiphon plants at Te Raoa Bay
11   04      WAIKARETAHEKE RIVER                                       on Lake Waikaremoana during routine surveillance.  A multi-
12   4.1     Hydrology                                                 agency response is well underway to manage the incursion,
12   4.1.1   Lake Kaitawa                                              involving DOC, tangata whenua, National Institute of Water and
12   4.1.2   Waikaretaheke River from Kaitawa Spillway to              Atmospheric Research, HBRC, Fish and Game, user groups and
             Lake Whakamarino                                          Genesis Energy.  A Ten-Year Strategic Plan has been prepared
13 4.1.3     Lake Whakamarino                                          and ratified by the governance group this reporting period
13 4.1.4     Waikaretaheke River below Piripaua Power Station          and regular dive inspections have reduced the biomass of
13 4.1.5     Maximum Flows: Waikaretaheke River and Lakes              Lagarosiphon at all known sites to very low levels (see Section
             Waikaremoana, Kaitawa and Whakamarino                     6.6 for details).
13   4.2     Aquatic Ecosystems and Water Quality
                                                                       Piripaua Transformer Upgrade After 73 years of service the two
13   4.2.1   Macro-Invertebrates
                                                                       original transformers at Piripaua Power Station were replaced
14   4.2.2   Waikaretaheke River Ecologial Assessment Below Piripaua
                                                                       during the reporting period. This was a massive undertaking
14   4.2.3   Waikaretaheke River Trout
                                                                       with the new units sourced from Korea. A multitude of other
14   4.2.4   Tune (eel) Migration Programmes
                                                                       work was also undertaken during the four month outage (see
16   4.3     Water Quality
                                                                       Section 5.1.3 for details).
16   4.3.1   Routine Monitoring
16   4.4     Sediment (Erosion, Transport and Deposition)              Tuna Migration Programme A record number of elvers (32,984)
17   4.5     Recreation and Tourism                                    were captured below Piripaua Power Station and transferred
17   4.5.1   Piripaua Power Station                                    to upstream habitats. Planning is also well underway to install
17   4.5.2   Whakamarino Dam                                           a migrant tuna by-pass which will provide a safe passage for
18   05      SCHEME-WIDE OUTCOMES                                      migrant tuna out of Lake Whakamarino into the Waikaretaheke
19   5.1     Maintenance Activities                                    River. The by-pass will be completed in the next reporting
19   5.1.1   Scheme-wide Maintenance Consent                           period (see Section 4.2.4 for details).
19   5.1.2   Piripaua Intake Weed Accumulation
19
20
     5.1.3
     5.1.4
             Piripaua Transformer Upgrade
             Waikaremoana Transmission Condition Assessment
                                                                       ABBREVIATIONS
20   5.2     Sports Fish and Habitat Enhancement Fund                  AER        Annual Environmental Report
21   5.3     Dam Safety                                                CSR        Comprehensive Safety Review
21   5.4     Oil Spill Response                                        DOC        Department of Conservation
21   5.5     Public Complaints                                         ECNZ       Electricity Corporation of New Zealand
21   5.6     Publicly Available Hydrology Information                  EMS        Environmental Management System
                                                                       EPT        Ephemeroptera, Plecoptera, and Trichoptera
22 06        COMMUNITY & ENVIRONMENTAL INITIATIVES                                (the three insect orders commonly used to test water quality)
23 6.1       Lake Waikaremoana Hapu                                    GPS        Global Positioning System
             Restoration Trust Partnership                             GWh        Gigawatt hour
23   6.2     Whio Forever                                              HBCC       Hawkes Bay Canoe Club
24   6.3     Waikareiti Biodiversity Project                           HBRC       Hawkes Bay Regional Council
25   6.4     Waimako Marae DIY                                         LWHRT      Lake Waikaremoana Hapu Restoration Trust
25   6.5     Lake Waikaremoana Challenge                               masl       meters above sea level – Moturiki Datum
26   6.6     Aquatic Weeds                                             MPI        Ministry of Primary Industries
                                                                       MVA        Megavolt Amp
27 07        KEY OBJECTIVES
                                                                       MW         Megawatt
28 7.1       Review of Key Objectives for 2012-13
                                                                       NIWA       National Institute of Water and Atmospheric Research
28 7.2       Key Objectives for 2013-14
                                                                       NZTA       New Zealand Transport Authority
29 08        REFERENCES                                                QMCI       Quantitative Macro-invertebrate Community Index
                                                                       RCMS       Resource Consent Management System
                                                                       SPI        Submerged Plant Indicators
                                                                       WERP       Waikaremoana Ecological Restoration Programme
                                                                       WPS        Waikaremoana Power Scheme
                                                                       WSFF       Waikaremoana Sports Fish and Habitat Enhancement Fund

                                                                       Front cover photo: Diver working on Number 2 siphon - Onepoto Siphon,
                                                                       Lake Waikaremoana, 1946.

                                                                       Back cover photo: Transporting pipe during construction of the
                                                                       Waikaremoana Power Scheme, 1946
WAIKAREMOANA POWER SCHEME
01 INTRODUCTION                                                         The first five-yearly review was in 2004 and at this time Genesis
                                                                                             Energy sought changes to the monitoring and reporting conditions
                     Nau mai haere mai ki tenei Ripoata Taiao e pa ana ki te mahi            to allow for more targeted monitoring programmes at Lake
                     hihiko mo tenei rohe o Waikaremoana.                                    Waikaremoana and on the Waikaretaheke River. The Hawkes Bay
                                                                                             Regional Council (HBRC) adopted the recommendations and these
                     Welcome to the 2012-2013 Annual Environmental Report (AER)
                                                                                             were incorporated into the Lake Waikaremoana Monitoring Plan
                     for the Waikaremoana Power Scheme (WPS).  The purpose of this
                                                                                             and the Waikaretaheke River Monitoring Plan.
                     report is to update communities and stakeholders on the wide
                     range of activities which occurred at the WPS between July 2012         The second opportunity for a five-yearly review occurred in 2009;
                     and June 2013.  It is the seventh AER for the WPS and follows from      however a review of the resource consents was not requested by
                     previous year’s reporting.  This report will:                           Genesis Energy nor undertaken by HBRC.
                         provide an overview of resource consent compliance                  Up until February 2013, resource consents for routine
                         at the WPS;                                                         maintenance activities around the WPS were generally applied
                         provide an update on monitoring and research programmes;            for on an as-required basis.  However during the reporting
                         report back on key projects;                                        period, scheme-wide resource consents to undertake various
                         report on community and environmental initiatives; and              routine maintenance activities at the WPS were granted by
                         define environmental objectives for the next 12 months.             HBRC. Similar maintenance consents have been in place at the
                                                                                             Tongariro Power Scheme since 2004 and they have proven to be an
                     Genesis Energy aims to be accessible to the public, to address
                                                                                             efficient mechanism to undertake routine maintenance activities,
                     issues as they arise and to develop closer working relationships
                                                                                             whilst effectively managing the effects of the activities on the
                     within the communities within which it operates.
                                                                                             environment (see Section 5.1.1).
                     1.1 DOCUMENT OVERVIEW
                                                                                             1.3 HOW TO USE THIS DOCUMENT
                     Genesis Energy produces a suite of reports and other
                                                                                             This report documents environmental outcomes based on two key
                     documentation on its activities each year (Figure 1).  These include
                                                                                             geographical features:
                     detailed technical reports, audit reports and various reporting
                     requirements to stakeholders.  They address specific issues at a            Lake Waikaremoana;
                     site/local level.                                                           Waikaretaheke River.
                     The Company’s Annual Report details Genesis Energy’s                    The report also provides information for:
                     performance as a company and sets objectives for the coming year.
                                                                                                 Scheme-wide Outcomes;
                                                                                                 Community and Environmental Initiatives.

                                                                                             ‘Bold text like this’ will help you to find your way around the
                                                                                             report.  This identifies the parts of the report that relate to specific
                                                                                             resource consent conditions.

                                                                                             Consent Description  Consent # (condition)

                                                                                             ‘Orange text like this’ throughout the report provides useful
                                                                                             background information on specific issues.

                                                                                             1.4 GENESIS ENERGY’S APPROACH
                                                                                             TO ENVIRONMENTAL MANAGEMENT

                                                                                             1.4.1 GENESIS ENERGY’S VALUES

                                                                                             Genesis Energy’s four core values define the way things are done
                                                                                             at Genesis Energy.  They are the actions and behaviours which
                                                                                             help contribute to the success of the company.

                                                                                             Genesis Energy’s Values are:
                        FIGURE 1 // Report hierarchy at Genesis Energy.
                                                                                                 Respect – We treat people and places as we would
                                                                                                 wish to be treated
                     This AER bridges the gap between site specific reporting and                Drive – We achieve with energy, courage and commitment
                     the company’s Annual Report.  It provides an overview of all                Imagine – We challenge today and change tomorrow
                     environmental and stakeholder activities relating to the WPS.  It           Support – We work together, take responsibility and have fun
                     does not overview company strategy or performance (refer to the         Genesis Energy’s intent is to become the preferred provider of
                     Annual Report for this information) or provide extensive detailed       energy in New Zealand.  We will achieve this by:
WAIKAREMOANA // 13

                     information on all monitoring programmes and initiatives undertaken
                     (refer to specific technical reports listed in the references).             Delivering efficient service and smart solutions to customers;
                                                                                                 Optimising the performance of our generation portfolio;
                     More information about Genesis Energy, including an electronic              ‘Living’ our values; and
                     copy of this document, can be found on the website                          Operating in a way that is safe and healthy for our people,
                     www.genesisenergy.co.nz                                                     our customers, our communities and the environment.
                     1.2 RESOURCE CONSENT PROCESS OVERVIEW                                   1.4.2 ENVIRONMENTAL MANAGEMENT SYSTEM
                     Resource consents for the on-going operation of the WPS were            Genesis Energy has an Environmental Management System
                     granted in November 1998.  This followed a period of intensive          (EMS) which ensures that environmental and social awareness
                     consultation, technical assessments, recommendations and                are core to the operation of the Company.  The EMS sets out the
                     review via a formal consultative group, and through one on one          Company’s values in respect of environmental and stakeholder
                     consultation with affected and interested parties.  The consultation    management, and clearly states its commitment to compliance
                     process addressed numerous issues and in most cases outcomes            with all environmental legislation.
                     were agreed.  Forty-five resource consents were granted for a
02

                     term of 35 years, subject to a range of conditions, including a five-
                     yearly review.
WAIKAREMOANA POWER SCHEME
Genesis Energy’s Environmental Values are:                              Data collected by the hydrology team is audited by an independent
                                                                        third party on at least an annual basis to maintain a high level of
    Act with integrity at all times.                                    transparency and external credibility and ensure data is being
    Foster close relationships with the community and                   collected and processed to a high standard.
    stakeholders, so that their views can be incorporated into the
    environmental decision-making processes.                            1.5 FEEDBACK
    Acknowledge that our activities affect both the environment
    and the communities within which we operate.                        Genesis Energy has worked to make this report informative and
    Respect the role of tangata whenua as kaitiaki of the natural       easy to understand.  Your feedback is welcome on both content
    resources and taonga within their rohe.                             and layout.  Contact details are as follows:
    Investigate to better understand the nature of the                  Renewable Energy – Tokaanu Power Station
    environmental effects – and share this information with the         State Highway 47
    community and stakeholders.                                         Private Bag 36, TURANGI 3353
    Seek environmental improvements in all aspects                      Phone (07) 384 7200
    of our business.

During the reporting period Genesis Energy began a review of its
EMS. This is to ensure that it encompasses the number of different
business systems used by the environmental teams and to ensure
that they are integrated with other core business systems, for
example the Resource Consent Management System. The review
is also checking that the EMS applies to all activities involving the
use of natural and physical resources and the environment, from
the conceptual stage of any project through to normal operational
activities of Genesis Energy. The review will be completed in the
2013/14 reporting period.

1.4.3 RESOURCE CONSENT MANAGEMENT SYSTEM

To help manage compliance across all generation sites, Genesis
Energy has developed a Resource Consent Management System
(RCMS).  This system holds all information relating to resource
consents, third party agreements, and permitted activities,
and defines, prompts and monitors actions required by their
conditions, and reports on the status of these.  The purpose of the
RCMS is to ensure that Genesis Energy manages its statutory and
stakeholder obligations effectively and that essential requirements
are not overlooked.

All Genesis Energy staff can access the RCMS through the
company’s intranet but only designated administrators within the
Environmental Team can make changes and update/sign off tasks,
or view potentially confidential information contained within third
party agreements.

An internal RCMS and environmental compliance audit is
undertaken on an annual basis at selected generation sites.
The purpose of the audit is to ensure the correct procedures are
being followed and identify any improvements that could be made
to RCMS systems or processes to best achieve 100% compliance.

A RCMS and environmental compliance audit for the WPS is
scheduled for July 2013 and will be reported on in the AER
reporting period 2013/14. During the reporting period, required
improvements to the RCMS were identified including enhanced

                                                                                                                                              ENVIRONMENTAL REPORT // 13
reporting functionality and ensuring that the system is more user-
friendly. A project is planned to incorporate these changes in the
RCMS in the 2013/14 reporting period.

1.4.4 HYDROLOGY

Genesis Energy has an extensive hydrology monitoring network
around the WPS.  A variety of flow, water level, water quality and
rainfall data is collected in real-time and telemetered near real-
time.  This information is sent to Genesis Energy’s Renewable
Energy Control Centre, located near Turangi, together with a range
of plant and market information.

During the reporting period the hydrology team has put an
extensive amount of work into improving the monitoring network
which has resulted in a high level of compliance along with more
efficient operation of plant for Genesis Energy. An example of an
upgrade that occurred during the reporting period was switching
the back-up data communications from radio to a cellphone
network which provide a more reliable, accurate and complete
records and are part of a holistic approach towards improving
the hydrological network. The hydrology team has supported the
                                                                                                                                              03

implementation of key environmental projects with their technical
expertise and ability to share this with stakeholders.
WAIKAREMOANA POWER SCHEME
02
                     WAIKAREMOANA
                     POWER SCHEME
WAIKAREMOANA // 13
04
WAIKAREMOANA POWER SCHEME
02 WAIKAREMOANA POWER SCHEME
                                                                           TABLE 1 // Average monthly inflows into Lake Waikaremoana during
The Waikaremoana Power Scheme (WPS) is located within and                  the reporting period.
adjacent to Te Urewera National Park in the northern Hawkes Bay
Region. The location and features of the scheme are shown on the         Month                2012-13               Long Term        Percent of
map inside the back cover.                                                                    Average           average Inflow      Average (%)
                                                                                                Inflow         (1930 - present)
The potential for power generation from the outflow of Lake                                     (m3/s)                   (m3/s)
Waikaremoana was recognised in the 19th century (Natusch,
                                                                         July                     24.9                    28.07            89%
1992) and three power stations were commissioned between 1929
and 1948. The WPS uses water from Lake Waikaremoana and the              August                  20.15                    25.53            79%
Waikaretaheke River and a number of its tributaries to generate
                                                                         September               17.87                    21.12            85%
electricity at three hydroelectric power stations – Kaitawa (36
megawatts [MW]), Tuai (60 MW) and Piripaua (42 MW). Water is             October                 12.45                    17.38            72%
taken from Lake Waikaremoana via tunnels at Onepoto Bay and is           November                 7.64                    13.67            56%
passed through Kaitawa Power Station before being discharged
into Lake Kaitawa. It is then passed through Tuai Power Station          December                 6.32                    11.29            56%
and discharged into Lake Whakamarino. From here, a further               January                  4.32                    10.12            43%
tunnel and penstocks carry the water to Piripaua Power Station
                                                                         February                 1.88                    10.91            17%
before it is discharged back into the Waikaretaheke River, the
natural outlet of Lake Waikaremoana.                                     March                    2.19                    12.37            18%

The generating plant has undergone major refurbishment over              April                    4.79                    15.27            31%
the past twenty years and the scheme’s generation capacity has           May                     10.88                    20.13            54%
increased from 124 to 138 MW. Operation of the WPS depends on
                                                                         June                    19.88                    23.56            84%
the demand for electricity and the availability of water. Electricity
from the WPS feeds into the national electricity grid and assists in     Annual Average           11.2                      17.5           64%
maintaining voltage levels on the transmission system.

Supply of electricity to the East Coast from the WPS is important
for two reasons. Firstly, the generators at Waikaremoana provide
voltage support for the Gisborne and Tokomaru Bay Transpower
transmission circuits. Secondly, the close proximity of the WPS
to Gisborne results in lower transmission losses, which reduces
the need for generation overall. The WPS is also ideally situated
to provide power to the East Cape area when the East Cape loses
connection to the national grid.

2.1 OPERATING THE WAIKAREMOANA POWER SCHEME

The WPS is operated remotely from Genesis Energy’s Renewable
Energy Control Centre, which is part of the Tongariro Power
Scheme near Turangi.  A 24/7 Generation Control team runs the
WPS as effectively and efficiently as possible using a variety of
flow, water level and rainfall data, as well as a range of plant and
market information to optimise electricity generation revenue
requirements while maintaining compliance with resource consent
conditions and operating within the electricity market rules.  A
complex operational control system that underwent a significant
                                                                           FIGURE 2 // Modelled inflows and rainfall for Lake Waikaremoana
upgrade in 2010 assists the operations team, providing details on
                                                                           during the reporting period.
all aspects of the scheme, enabling remote control and alerting
the operators when various parameters trend outside of their
standard operating limits (including resource consent limits).
                                                                        The WPS generated a total of 249 Gigawatt hours (GWh) of
There is a full maintenance team at the WPS with roaming
                                                                        electricity (Table 2), again significantly below the long-term

                                                                                                                                                   ENVIRONMENTAL REPORT // 13
Controllers on site.  These Controllers are available 24/7 to fix
                                                                        average (approximately 450 GWh). This reflects the weather
faults or defects as they arise.
                                                                        conditions during this reporting period as well as significant
2.2 CLIMATE AND POWER GENERATION                                        outages which took place, such as the Piripaua transformer
                                                                        upgrade (see Section 5.1.3), which reduced the generation capacity
The Lake Waikaremoana catchment had below average rainfall              of the scheme significantly.
over the reporting period.  Inflows were steady at just below the
long-term average during July to October 2012 (Table 1), however,       Based on an average figure of electricity consumption per
this dropped away significantly through the summer months as            household of 7,760 kWh/yr (Ministry of Economic Development,
the East Coast entered into a period of drought. The combined           2012; p121) the 249 GWh produced by the WPS in the reporting
average inflows for February and March were the lowest on record        period was enough electricity to power the annual demand of
since 1982. Inflows for the year overall were 64% of the long-term      approximately 32,000 households.
average (1930 – present).

There were no significant inflow events during the reporting period        TABLE 2 // Waikaremoana Power Scheme generation
                                                                           during the reporting period.
(Figure 2) and the lake was able to be maintained between 26%
and 65% full.
                                                                         Site                                                Generation (GWh)
The total rainfall recorded at Onepoto for the reporting period was
                                                                         Kaitawa                                                             36
1,487 mm, well below the long-term average at this site (1,939 mm).
July 2012 had the highest monthly rainfall with 245.8 mm while           Tuai                                                                130
February 2013 had the lowest monthly rainfall with just 59.6 mm.         Piripaua                                                            83
                                                                                                                                                   05

                                                                         Total                                                               249
WAIKAREMOANA POWER SCHEME
06   WAIKAREMOANA // 13

                          03
                          LAKE
                          WAIKAREMOANA
WAIKAREMOANA POWER SCHEME
03 LAKE WAIKAREMOANA                                                       event-driven monitoring to assess the impact of lake
                                                                           level excursions outside of the operating range on shoreline
Lake Waikaremoana was created approximately 2200 years ago                 morphology and vegetation;
by a massive landslide that dammed the Waikaretaheke River.                a third party agreement with DOC with a focus on ecological
The landslide created a steep natural dam face at the head of the          enhancement on the shore of Lake Waikaremoana;
valley down which the Waikaretaheke River once flowed.  Below              a third party agreement with Fish and Game Council of
this natural dam, the Waikaretaheke River was fed by water                 New Zealand to increase angler opportunities in the
leaking through the dam.                                                   Hawkes Bay Region.
                                                                           In association with DOC and the Royal Forest and Bird
Lake Waikaremoana is the primary hydro-storage lake for the
                                                                           Protection Society, Genesis Energy undertook a project to
Waikaremoana Power Scheme (WPS).  The lake has a surface
                                                                           enhance the Onepoto Gatehouse area (a main access point
area of approximately 53 km2 and an operating range of three
                                                                           for the Great Walk track) by planting native species and
metres, from 580.29 to 583.29 masl.  In 1946 the level of Lake
                                                                           erecting information panels.
Waikaremoana was lowered by five metres to facilitate the
operation of the WPS (Figure 3).  The natural lake level range was     3.1 HYDROLOGY
approximately seven metres.
                                                                       Lake Waikaremoana has a normal operating range from 580.29
                                                                       to 583.29 masl. Genesis Energy must release a controlled
                                                                       discharge from the lake (Table 3) if the maximum lake level is
                                                                       reached or exceeded.
                                                                       Lake Waikaremoana HBRC WP982030Mc (3,4)

                                                                       During the reporting period a variation was obtained to resource
                                                                       consent WP982030Mc as part of the scheme-wide maintenance
                                                                       consent acquisition (see Section 5.1.1) to allow for temporary
                                                                       cessation of controlled discharge for maintenance purposes,
                                                                       for example to allow for the safe removal of  obstructions from
                                                                       intake screens.

                                                                          TABLE 3 // Controlled discharge rates from Lake Waikaremoana
                                                                          when lake level exceeds 583.29 masl.

                                                                        Lake level (m)                            Controlled discharge (m3/s)
                                                                          583.29                                        No Controlled Release
                                                                          583.29                                                             43
   FIGURE 3 // Water level at Lake Waikaremoana
   (1929–30 June 2013).                                                   583.49                                                             47
                                                                          583.69                                                             51
                                                                          584.09                                                             55
Lowering the lake level and narrowing the lake level range
changed the energy of waves acting on the shoreline.  Lake             Genesis Energy constantly monitors the level of Lake
Waikaremoana has always experienced significant fluctuations           Waikaremoana. A three hour average lake level is used to assess
in level, and these fluctuations had significant effects on the        lake level compliance. This average helps to remove sieche and
character of the pre-1946 shoreline (large eroded shoreline scarps     wave effects from the lake level record.  Figure 4 shows the level
are evident in many places).  Some on-going erosion and change         of Lake Waikaremoana for the reporting period.
is entirely natural, even though the lake is now managed within a
three metre operating range.

Lowering the lake level directly affected the shoreline, creating
large, flat, unvegetated areas.  These have subsequently been
utilised for assets such as the campground at Home Bay and
related sewage ponds (which have now been relocated away from

                                                                                                                                                  ENVIRONMENTAL REPORT // 13
the lake shore), Department of Conservation (DOC) huts and parts
of the Great Walk track.

After the lake level was lowered, attempts were made to seal
leaks in the natural dam by constructing rock filter blankets in the
lakebed at Te Wharawhara Bay.  Combined with the lake lowering,
sealing the lake reduced leakage through the natural dam from
approximately 17 cubic metres per second (m3/s) to 5 m3/s,
making more water available for electricity generation.

Key outcomes of the resource consents process in 1998 and the
subsequent change of resource consent were:

    a three metre operating range for the lake, with specific
    conditions controlling discharges above and below the                 FIGURE 4 // Level of Lake Waikaremoana for the reporting period.
    operating range;
    preparation and implementation of the Lake Waikaremoana
    Monitoring Plan which includes information on:

         hydrology;                                                    Lake level compliance for Lake Waikaremoana for the reporting
         terrestrial shoreline vegetation;                             period is detailed in Table 4.  The lake did not exceed the
         shoreline morphology;                                         maximum control level during the reporting period.
                                                                                                                                                  07

         littoral ecology;
         brown trout.
WAIKAREMOANA POWER SCHEME
The key purpose of shoreline vegetation monitoring is to assess
                        TABLE 4 // Lake Waikaremoana level compliance during                 the effects of the lake level management regime on terrestrial
                        the reporting period.                                                vegetation structure and development.

                      Parameter         Value (masl)   Compliance (%)     Consent Number     A total of 100 vegetation transects and/or photo-points have been
                                                                               (condition)   established around the Waikaremoana shoreline since 1999.
                                                                                             These monitoring sites represent a full range of shoreline profiles,
                      Minimum level           580.29               100    WP982030MB (3)
                                                                                             substrates and habitat types. Shoreline vegetation transects are
                      Maximum level           583.29               100    WP982030MB (3)     surveyed every five years and photo-points are surveyed annually.
                                                                                             They provide baseline data which enable detection of even minor
                     Outflows from Lake Waikaremoana are limited by the permeability         changes in vegetation related to lake level variation.
                     of the dam wall and the flow that can be taken through Genesis          Monitoring since 1999 indicates that fluctuations in lake level
                     Energy structures.  Genesis Energy can only take water from             within the three metre operating range have resulted in detectable
                     Lake Waikaremoana via a siphon system, through Kaitawa Power            changes to the terrestrial vegetation. The ecological effect of these
                     Station, or via a spillway (at very high lake levels).  The maximum     changes, however, is minor and is comparable to that which would
                     rate of take through each structure is related to the design of the     occur naturally on similar lake shorelines. A lake level regime
                     system.  The design criteria of these structures are defined in         reflecting the natural range of over seven metres would result in
                     resource consents.  There have been no changes to the structures        far more dramatic changes (Single & Shaw, 2005).
                     during the reporting period.
                     Lake Waikaremoana HBRC WP982010Ta;                                      The key driver of vegetation change at Lake Waikaremoana is the
                     HBRC WP982001Ta;                                                        length of time that the lake spends above or below certain levels.
                     HBRC WP982003Ta                                                         Prolonged high lake levels enable turf communities to establish
                                                                                             at high elevations but will also kill terrestrial species that cannot
                     3.1.1 LEVEL TRENDS AT LAKE WAIKAREMOANA
                                                                                             tolerate prolonged submergence.  Prolonged low lake levels
                     Pre-construction of the power scheme, lake levels were generally        have the opposite effect: turf communities dry out and terrestrial
                     high heading into summer, reducing during summer and autumn             species are able to establish at lower elevation, where they are at
                     and increasing during winter and spring.  Lake Waikaremoana is          risk of submergence when the level increases again.
                     managed to reflect this natural cycle.  During the reporting period
                                                                                             In 2005, in line with a change of resource consent, the original
                     the lake level mimicked this natural pattern of variability closely
                                                                                             monitoring programme (Shaw, 1998) was formally revised and
                     by rising to its highest level in early summer and dropping steadily
                                                                                             vegetation and shoreline morphology monitoring became more
                     through to late autumn. Since late April the lake has been rising
                                                                                             integrated (Single 2005; Single and Shaw 2005).
                     with early winter inflows and as a result of reduced water usage
                                                                                             Lake Waikaremoana HBRC WP982030Mb (11-12)
                     due to maintenance projects such as the Piripaua Transformer
                     Upgrade (see Section 5.1.3) (Figure 5).                                 The annual Lake Waikaremoana shoreline inspection, involving
                     Lake Waikaremoana HBRC WP982030Mb (4)                                   circumnavigation of the entire shoreline, rephotographing, and
                                                                                             evaluating all photo-points, was undertaken in February 2013.
                                                                                             Details of the key findings are reported by Wildland Consultants
                                                                                             Ltd (Wildlands, 2013).

                                                                                             Changes to the shoreline vegetation and profiles in the reporting
                                                                                             period were very minor, and no change was evident for 88% of
                                                                                             regularly monitored sites. There were very minor physical changes
                                                                                             to the shoreline. Minor changes in the distribution of shoreline
                                                                                             species was related to their tolerance of submergence. Minor
                                                                                             changes occurred locally on the following four shoreline types:

                                                                                                 Stream Sedimentary Fans;
                                                                                                 Wave Cut Terrace with Scarp;
                                                                                                 Wave Cut Terrace - Gentle Slope;
                                                                                                 Rock Platform or Pavement Overlain with Wave Cut Terrace.

                                                                                             No change was noted on the following six shoreline types:

                                                                                                 Sandstone boulders grading back into wave cut terrace (four sites);
                                                                                                 Rock headland;
                                                                                                 Pocket beach;
                        FIGURE 5 // Lake Waikaremoana inflows and level during the               Blocks boulders;
                        reporting period.                                                        Cliffs;
                                                                                                 Narrow sandy beach.
WAIKAREMOANA // 13

                                                                                             Wildland Consultants advise that ensuring that high lake levels
                     3.2 ECOSYSTEMS AND WATER QUALITY                                        are attained from time-to-time (around the top of the operating
                                                                                             range and just above) should be seen as a positive influence
                     The Lake Waikaremoana Monitoring Plan defines the type and              on lakeshore ecology.  In ecological terms, there are no new
                     frequency of monitoring to be undertaken on Lake Waikaremoana.          observations of changes or developments on the shoreline that
                     This section describes the current programmes from ecosystem            give cause for any concern.
                     and water quality perspectives.
                                                                                             The next annual photo-point inspections will be undertaken in
                     3.2.1 TERRESTRIAL VEGETATION                                            March 2014, and the next five-yearly vegetation transect re-
                     The natural vegetation around the shore of Lake Waikaremoana is         measurement is due in March 2016.
                     a significant feature of the lake.  Much of the post-1946 exposed       3.2.2 AQUATIC VEGETATION
                     shoreline is now covered with indigenous vegetation, with
                     localised areas of exotic grassland, particularly on the more fertile   Lake Waikaremoana has high native aquatic plant species
                     old river delta shorelines.                                             diversity and contains the best remaining example of native
                                                                                             aquatic vegetation assemblages in a large, deep, clear lake in
08

                                                                                             the North Island. Aquatic plants (macrophytes) provide substrate
for epiphytic algae, upon which many littoral (shallow shoreline)        3.2.3 TROUT MONITORING
macro-invertebrates feed. As such, maintenance of the littoral
zone is important to the productivity and ecology of the lake.           Brown and rainbow trout were introduced into Lake Waikaremoana
Changes in aquatic macrophyte communities may result from                in 1896 for recreational angling. The resultant fishery is now
prolonged periods of lowered water levels which have the                 considered to be of national importance. During summer, brown
potential to expose shallow-water plant communities. Narrowing           trout live in the lake’s littoral zone.
the overall lake level operating range also has the potential to
                                                                         A key feature of the Lake Waikaremoana brown trout fishery is the
change the macrophyte species composition. Monitoring of these
                                                                         opportunity for anglers to stalk around the shoreline spotting and
communities is, therefore, an important part of lake management.
                                                                         fishing to brown trout feeding in the shallow lake margins.  Lake
Lake Waikaremoana HBRC WP982030Mb (15-16)
                                                                         levels can affect this angling opportunity by altering the amount
The littoral aquatic macrophyte vegetation of Lake Waikaremoana          of shoreline physically accessible during spring and summer.
is monitored every five years along 17 transects within the lake.        High lake levels restrict the number of shoreline sites available
Prior to this year, the last survey was undertaken in February           for angling and accessibility for moving between fishing sites
2008. During the reporting period the 17 transects were re-              as there is limited room to wade around the shoreline between
surveyed and the depth ranges, coverage, and heights of each             the water’s edge and the vegetation.  There is also very limited
macrophyte species recorded. Details of the key findings are             room for fly fishermen to back-cast: the curtain of vegetation
reported by NIWA (Wells & Winton, 2013).                                 close to the water’s edge limiting the amount of fishable water
                                                                         for this technique.  Fewer places to fish result in more frequent
Twenty-two species of submerged macrophytes were recorded in             encounters with other anglers, more fishing pressure at the fewer
2013 with native plants most prevalent. The three main macrophyte        fishable sites and consequently lower catch rates.   In the past,
communities present in the lake were: the amphibious short               Genesis Energy was required to quantify the change in shore-
shallow-water community, tall vascular community and deeper              based angling opportunity as a result of lake level changes.
charophyte community. Elodea was the most abundant exotic                This consent requirement was completed between November
species and dominated the tall growing vascular community in             2008 and March 2010 and was reported in the 2009/10 Annual
sheltered sites, such as Home Bay, but mostly co-existed with            Environmental Report for the Waikaremoana Power Scheme
native species rather than displacing them in the main body of           (Genesis Energy, 2010).
the lake. Lagarosiphon was not found on any of the profiles but is
present in the lake and the subject of an eradication programme          Lake level manipulation also has the potential to affect the littoral
supported by Genesis Energy (see Section 6.5).                           ecosystem and therefore, could adversely affect both juvenile
                                                                         trout habitat and adult growth rates. Between 2000 and 2005, a
Overall any differences compared to previous surveys were small          brown trout monitoring programme was undertaken to assess
with the lake vegetation continuing to occupy more than a 20 m           any potential adverse effects of the current operating regime
depth range (Figure 6), where conditions (such as slope, substrate       (Pitkethley and Kusabs, 2005). Brown trout population estimates
and exposure) were favourable, with similar species composition.         for Lake Waikaremoana were originally indexed by counting
Continued high values for cover, species diversity and depth range       spawning adult trout in the Waiotukupuna Stream, one of the
of lake vegetation indicated no change in lake ecological condition.     major spawning streams.  However, these estimates were not
Lake SPI (Submerged Plant Indicators) indices also confirmed the         considered satisfactory and a 5-yearly intensive trapping operation
stability of lake condition over the last 10 years with no significant   of spawning trout on the Waiotukupuna Stream has been
changes between consecutive surveys. Lake Waikaremoana is                instigated in its place.
categorised as being in a high ecological condition with a Lake SPI      Lake Waikaremoana HBRC WP982030Mb (17-18)
Index of 74%. This reflected the very high floristic values in the
lake (Native Condition Index, 77%) and low impact from invasive          The Waiotukupuna Stream fish trap was operated for a minimum
species (Invasive Impact Index, 26%).                                    of 10 nights per month over the 2009 winter period (May – August).
                                                                         The next five-yearly assessment of trout populations is due in the
As there is a close relationship between aquatic plants and              winter of 2014.
dependent macroinvertebrates, the continued good status of the
lake vegetation indicates that the macroinvertebrate community           3.2.4 ECOLOGICAL RESTORATION PROGRAMME
is likely to be healthy. Wells & Winton (2013) conclude that fish
                                                                         During the resource consents process many complex issues were
dependent on invertebrates as a food source would not have been
                                                                         raised and worked through with the Department of Conservation
affected by lake level fluctuations disrupting their food source.
                                                                         (DOC).  Some of these issues were addressed through consent
The next littoral aquatic macrophyte vegetation survey is due in         conditions and the development of monitoring programmes;
February 2018.                                                           others were mitigated via a 10-year agreement with DOC.
                                                                         Under this agreement, known as the Waikaremoana Ecological

                                                                                                                                                 ENVIRONMENTAL REPORT // 13
                                                                         Restoration Programme (WERP), Genesis Energy provided funding
                                                                         to DOC for ecological enhancement around the shore of the lake.

                                                                         The original focus of WERP was to help secure a viable kiwi
                                                                         population on the Puketukutuku Peninsula.  Over time,
                                                                         management of the kiwi programme on Puketukutuku Peninsula
                                                                         transferred to the Lake Waikaremoana Hapu Restoration
                                                                         Trust (LWHRT) and their increasing contribution to the kiwi
                                                                         programme allowed DOC, with the LWHRT’s support, to focus on
                                                                         other threatened species such as: whio (blue duck), ngutukaka
                                                                         (kaka-beak), Powelliphanta snails, mistletoe and Dactylantus
                                                                         (wood rose).  The WERP agreement with DOC concluded in
                                                                         2008, although Genesis Energy continues to support the kiwi
                                                                         programme via an agreement with the Lake Waikaremoana Hapu
                                                                         Restoration Trust (see Section 6.1).

                                                                         While the original WERP agreement has now expired, Genesis
                                                                         Energy continues to work with DOC staff from the Bay of Plenty/
                                                                         East Coast Conservancy and tangata whenua on a new Genesis
   FIGURE 6 // Bottom limit of the charophyte community at Site 9,
                                                                         Energy sponsored biodiversity management project in the Lake
   Wairau Arm, 21 m deep.
                                                                         Waikareiti area (see Section 6.3).
                                                                                                                                                 09
3.3 SEDIMENT (EROSION, TRANSPORT AND DEPOSITION)

                     The sedimentary geology of the Lake Waikaremoana shoreline is
                     a significant natural feature. The Lake Waikaremoana Monitoring
                     Plan has been developed in part to assess the effects of the lake
                     level management regime on the structure and development of
                     shoreline landforms and erosion patterns.

                     Lowering the lake level in the 1940’s exposed large flat areas of
                     soft delta-sediment shorelines. These have subsequently been
                     used as sites for huts, tracks, camping grounds, sewage ponds
                     and other recreational and tourism assets. Shore change has
                     created hazards at some of these sites. Erosion, in particular,
                     threatens the viability of the assets and impacts on use of the
                     shoreline resource.

                     In 1999, Allan et al., developed an annual monitoring programme
                     which used a network of profiles and photo-points to assess
                     shoreline change and to determine the adequacy of existing
                     erosion protection works, and set timeframes for future erosion           FIGURE 7 // Photo shows stabilisation of previously eroding old
                     hazard management.  This programme was formally revised in                lake bed deposit at Home Bay (Photo: Shore Processes and
                     2005 and incorporated into the Lake Waikaremoana Monitoring               Management Ltd)
                     Plan. A significant change was the integration of DOC’s assets at
                     high erosion risk sites with the shoreline vegetation and erosion
                     monitoring programmes (Single 2005; Single and Shaw 2005).             The next annual inspection and photo-point survey is due in
                                                                                            March 2014, while the next shoreline profile transect resurvey is
                     The current comprehensive monitoring network is based on a
                                                                                            scheduled for 2016. This survey date will coincide with the five-
                     combination of beach profile and differential Global Positioning
                                                                                            yearly vegetation survey.
                     System (GPS) surveys, covering sites established in 1999–2000.
                     New sites were also established between 2004 and 2007. Annual          3.3.1 EVENT-DRIVEN MONITORING
                     photo-point records compliment five-yearly field transect
                     measurements, which are designed to assess:                            Lake Waikaremoana has a large catchment and a restricted outlet
                                                                                            and lake levels can rise very rapidly following heavy rainfall.
                         changes in profile form over time;                                 Vegetation within the 3 m operating range experiences dramatic
                         the stability of the shoreline;                                    changes, depending on whether it is submerged, and for how long.
                         rates of shoreline advance and retreat;                            The shoreline substrates also experience dramatic changes in
                         changes in the position or patterns of shoreline contours;         moisture levels and wave environments in relation to the degree
                         predictions of expected future shoreline changes;                  of inundation.
                         measurement of erosion rates on mudstone benches.                  Lake Waikaremoana HBRC WP982030Mb (11-14)
                     Monitoring identifies the magnitude and rates of shore change          Event-driven monitoring is required when lake levels exceed
                     around the lake for different shore types and for shores               583.29 masl or go below 580.29 masl for more than seven
                     with different wave exposure, and it will continue to provide          consecutive days. Event driven monitoring was not required during
                     benchmarks for future change.                                          the reporting period.
                     Changes during the monitoring period 1999–2005 occurred to
                     beaches, soft shores and mudstone benches. Variations between
                     annual surveys reflected the characteristics of wind, wave and water
                     level influences during the period between surveys. Overall, the
                     magnitude of change at Lake Waikaremoana is comparable to or
                     less than that measured on other New Zealand lakes (Single, 2005).

                     A Shoreline Hazard Management Report was also produced in
                     2010 (Single et al, 2010) and forwarded to DOC, Hawkes Bay
                     Regional Council and to local tangata whenua representatives.
                     The report presents information for managing the risk posed to
                     activities and assets around the shore of Lake Waikaremoana by
                     lake level changes. This report is a valuable resource to assist
                     future asset management on the Lake Waikaremoana shoreline.
                     Lake Waikaremoana HBRC WP982030Mb (13-14)

                     The annual Lake Waikaremoana shoreline inspection, involving
WAIKAREMOANA // 13

                     circumnavigation of the entire shoreline, rephotographing, and
                     evaluating all photo-points, was undertaken in February 2013.
                     Details of the key findings are reported by Shore Processes and
                     Management Ltd (Single, 2013).

                     The 2013 inspection of the shoreline of Lake Waikaremoana and
                     comparison to the photographic record showed no significant
                     physical shoreline changes at any of the monitored sites, nor on
                     other sections of the shore (Figure 7). There was no evidence of
                     water level or wave events significantly modifying or adjusting
                     the beaches. However mudstone shores developed friable shale
                     covering of the surface during the summer. This was more evident
                     on north facing shores.
10
RIVER
                                  WAIKARETAHEKE

11   ENVIRONMENTAL REPORT // 13
                                  04
04 WAIKARETAHEKE RIVER

                     The Waikaretaheke River is the natural outlet from Lake
                     Waikaremoana. Below the lake outlet, the river has cut into the
                     landslide debris creating a very steep, incised and fast-flowing
                     river system.

                     Damming the natural outlet, sealing spring leaks and creating
                     lakes for the purposes of power generation has modified the
                     upper Waikaretaheke River catchment. The river’s two man-
                     made lakes, Kaitawa and Whakamarino, have become renowned
                     trout fisheries: Lake Whakamarino, in particular, produces high
                     numbers of very large trout.

                     A change of resource consent in 2005 sought a more focused
                     and targeted monitoring programme for the Waikaretaheke
                     River, which is encompassed within the Waikaretaheke River
                     Monitoring Plan. The change of resource consent also allows for
                     improvements to the monitoring programmes to be made as more
                     information becomes available.                                           FIGURE 8 // Lake Kaitawa level during the reporting period.

                     Key outcomes of the 1998 resource consents process and the
                     subsequent change of resource consent were:

                         a 3.4 m operating range for Lake Kaitawa and a 1.8 m range
                         for Lake Whakamarino;                                             During the reporting period a variation was obtained to resource
                         a requirement to measure and record the amount of flow            consent WP982121Mb as part of the scheme-wide maintenance
                         in the Waikaretaheke River and the three power stations           consent acquisition (see Section 5.1.1) to allow for lowering
                         and to provide this data annually to the Hawkes Bay               the level of water in Lake Kaitawa by up to 1 metre below
                         Regional Council;                                                 the minimum operating level for the purpose of undertaking
                         minimum flows of 25 l/s downstream of the Waikaretaheke           maintenance and/or repair work. A number of conditions are
                         Diversion Structure and 5 l/s downstream of the                   associated with this resource consent including a requirement that
                         Whakamarino Dam;                                                  the lake level is not lowered during the month of October to avoid
                         a requirement to maintain the quality of water discharges         the opening of the fishing season (including Labour Weekend).
                         from the Waikaremoana Power Scheme;
                                                                                           During the reporting period, Lake Kaitawa achieved a very high
                         an agreement with the New Zealand Recreational Canoeing
                                                                                           level of compliance (Table 5). Only one minor non-compliance
                         Association – now known as Whitewater NZ – to provide
                                                                                           occurred during the reporting period where, for a period of ten
                         recreational kayaking opportunities within the Waikaremoana
                                                                                           minutes on 10 October 2012, Lake Kaitawa dropped below its
                         Power Scheme;
                                                                                           Minimum Control Level as a result of a tripping at the Kaitawa
                         an agreement with Transit New Zealand – now known as the
                                                                                           Power Station. A thorough investigation was undertaken and
                         New Zealand Transport Authority (NZTA) – to monitor erosion
                                                                                           appropriate actions put in place to prevent this from reoccurring
                         in the Waikaretaheke River;
                                                                                           in the future.
                         an agreement with Federated Farmers to provide minimum
                         flows as a stock barrier downstream of Piripaua Power Station;
                         preparation and implementation of the Waikaretaheke River            TABLE 5 // Lake Kaitawa level compliance during
                         Monitoring Plan that will include monitoring programmes for:         the reporting period.

                              macroinvertebrates below the Waikaretaheke                    Parameter          Value (masl)   Compliance (%)      Consent Number
                              Diversion Gates;                                                                                                         (condition)
                              the effect of recreational releases on trout in the river;
                              an elver trap and upstream transfer programme;                Minimum level             450.1              99.99    WP982121MA (3)
                              a mature eel downstream transfer programme;                   Maximum level             453.5               100     WP982121MA (3)
                              hydrology.
                                                                                           4.1.2 WAIKARETAHEKE RIVER FROM KAITAWA SPILLWAY
                     4.1 HYDROLOGY
                                                                                           TO LAKE WHAKAMARINO
                     4.1.1 LAKE KAITAWA
                                                                                           The damming and diversion of waters from the Waikaretaheke
                     Lake Kaitawa was formed following the construction of an earth        River by the Waikaretaheke Diversion Structure have reduced the
                     dam and weir across the Waikaretaheke River in the mid-1930s,         magnitude and variability of flows downstream, thereby reducing
                     converting a small spring-fed lake and wetland into a larger          the amount of habitat available for aquatic flora and fauna.
                     storage reservoir.  The water level was raised by approximately       Investigations into invertebrate populations have shown that the
WAIKAREMOANA // 13

                     3 m, creating a lake with a surface area of approximately 6.1         numbers in the river below the diversion structure are lower
                     hectares. The lake is fed by water diverted from the Waikaretaheke    than would naturally have occurred. A minimum flow of 25 l/s is
                     River and a number of springs that flow directly into the lake.       released downstream of the Waikaretaheke Diversion Structure to
                     Lake Kaitawa  HBRC WP982121Mb                                         provide some suitable habitat for native flora and fauna.
                                                                                           Waikaretaheke River  HBRC WP982320Mf (6, 8)
                     Lake Kaitawa is the headpond for Tuai Power Station.  The
                     operating range of the lake is 3.4 m, from 450.1 to 453.5 masl        To maintain the minimum flow of 25 l/s downstream of the
                     (Figure 8).  Water for the Tuai Power Station is taken through the    Waikaretaheke Diversion Structure, holes have been drilled
                     Tuai Intake, located on the eastern side of the lake, at a maximum    through the gate to release the desired amount of water.  Genesis
                     rate of up to 42 m3/s.  There is no minimum flow requirement in the   Energy staff check the holes weekly to ensure that they remain
                     Waikaretaheke River downstream of Lake Kaitawa, with seepage          free of any blockages.
                     and spring flows creating flow only a short distance downstream.
                                                                                           Genesis Energy hydrology staff undertake quarterly flow
                                                                                           gaugings downstream of the diversion structure to demonstrate
                                                                                           compliance.  All of the gauged flows for this reporting period were
                                                                                           above the minimum flows with full compliance being achieved.
12
Genesis Energy is required to close the Waikaretaheke Diversion          A minimum flow of at least 5 l/s is maintained in the
for two hours, whenever a flow of greater than 5 m³/s is spilled         Kahuitangaroa Stream immediately downstream of Lake
from Lake Kaitawa down the Waikaretaheke River.  Spill from              Whakamarino.  The minimum flow is based on leakage flow from
Lake Kaitawa is not permitted on the 1st of October, the first           the drainage galleries within the dam. This flow is monitored
weekend after 1st October, or during Labour Weekend, to reduce           three-monthly by Genesis Energy hydrology staff and was fully
discolouration in Lake Whakamarino during these important                compliant during the reporting period.
angling periods.
                                                                         4.1.4 WAIKARETAHEKE RIVER BELOW PIRIPAUA POWER STATION
This condition was not exercised during this reporting period.
Lake Kaitawa exceeded its Maximum Control Level only once                During the consent process, farmers along the Waikaretaheke
during the year which resulted in a spill flow of only 3 m³/s. The       River, downstream of Piripaua Power Station, raised concerns that
Waikaretaheke Diversion gate remained open as the flow did not           the river did not provide an adequate stock barrier during times
exceed the 5 m³/s required to initiate this condition.                   of low flow from Piripaua Power Station.  Following a number of
                                                                         flow trials, Genesis Energy reached an agreement with Federated
4.1.3 LAKE WHAKAMARINO                                                   Farmers to provide a minimum flow from Piripaua Power Station
                                                                         of 2 m3/s between 1 November and 31 March each year.
Lake Whakamarino was created following the construction
of an earth dam (which contains a spillway structure) across             The seasonal minimum flow below Piripaua Power Station, as
the Kahuitangaroa Stream. The lake has a surface area of                 agreed with Federated Farmers, was largely met during the
approximately 29.8 hectares. Water for the Piripaua Power Station        reporting period, except for four short periods between December
is taken through the Piripaua Intake, located on the south-eastern       2012 and March 2013. On these occasions there was no flow
side of Lake Whakamarino, at a maximum rate of up to 49 m3/s.            through the Piripaua Power Station as a result of operational or
Below Whakamarino Dam a continuous minimum flow of                       maintenance issues. Stakeholders were notified of these events
5 l/s is maintained.                                                     and no issues were raised. The dates and durations of each event
Lake Whakamarino  HBRC WP982420Mc (5)                                    are listed in Table 7.

During the reporting period a variation was obtained to resource
consent WP9824020Md as part of the scheme-wide maintenance                  TABLE 7 // Flow periods below the agreed 2 m³/s flow downstream
                                                                            of Piripaua Power Station.
consent acquisition (see Section 5.1.1) to allow for lowering
the level of water in Lake Whakamarino by up to 1 m below the
minimum operating level for the purpose of undertaking any                Date                    Duration   Minimum Flow               Reason
maintenance and/or repair work.                                           18/12/12                 4 hours     503 litres/sec       Transpower
                                                                                                                                     tripping at
Lake Whakamarino has a normal operating range of 1.8 m,                                                                               Redclyffe
from 246.3 to 248.1 masl (Figure 9).  There was one minor non-
compliance event during the reporting period which occurred               1/02/13                5.5 hours     404 litres/sec   Wicket gate link
                                                                                                                                         failure
on 29 April 2013 as a result of the lake dropping below the
minimum control level for 40 minutes (Table 6). During this               24/03/13                10 hours     438 litres/sec     Transformer
time, the minimum level that the lake reached was recorded as                                                                     Replacement
246.28 masl.  The event was caused by an equipment fault that             27/03/13                 5 hours     411 litres/sec     Transformer
resulted in incorrect information being displayed at the Generation                                                               Replacement
Control Centre – an issue that was rectified as soon as it became
apparent. There were no adverse environmental or ecological              4.1.5 MAXIMUM FLOWS: WAIKARETAHEKE RIVER AND LAKES
effects caused by this event and no complaints were received. The        WAIKAREMOANA, KAITAWA AND WHAKAMARINO
correct information is now displayed in the Control Centre.
                                                                         Resource consents specify maximum flow limits, based on design
                                                                         criteria, for several discharge control points (Table 8). There have
                                                                         been no modifications to any of these control points and therefore
                                                                         no alteration of their flow capacities.

                                                                         4.2  AQUATIC ECOSYSTEMS AND WATER QUALITY

                                                                         4.2.1 MACRO-INVERTEBRATES

                                                                         Studies of macro-invertebrate communities have been undertaken
                                                                         to assess the effect of reduced flows below the Waikaretaheke

                                                                                                                                                   ENVIRONMENTAL REPORT // 13
                                                                         Diversion structure, down to the Mangaone Stream confluence
                                                                         where flow recovery begins.  Based on the results of five years of
                                                                         data collected between 1999 and 2003, Scarsbrook and Bowman
                                                                         (2003) concluded that the timing of flow releases down the natural
                                                                         Waikaretaheke River channel was a more significant driver of
                                                                         macro-invertebrate community composition than the level of
                                                                         residual flow in the natural channel. Samples collected soon after
                                                                         flushing flows had downstream communities similar to those
                                                                         upstream, whereas samples collected after a long period without
   FIGURE 9 // Lake Whakamarino level during the reporting period.
                                                                         flushing flows had different assemblages to those expected in the
                                                                         Waikaretaheke River.
                                                                         Lake Whakamarino  HBRC WP982420Mc (9)
                                                                         Piripaua Power Station  HBRC DP982510Wb (11)
                                                                         Waikaretaheke River  HBRC WP982320Mf (13)
   TABLE 6 // Lake Whakamarino level compliance for
   the reporting period.                                                 The Waikaretaheke Monitoring Plan requires regular assessment
                                                                         of macro-invertebrate communities in the Waikaretaheke
 Parameter         Value (masl)   Compliance (%)      Consent Number     downstream of the diversion structure.  Macro invertebrate
                                                           (condition)   data was last collected from the Waikaretaheke River by Tonkin
                                                                         & Taylor in March/April 2009.  Their recommendation was
 Minimum level            246.3              99.99    WP982420MC (5)
                                                                         that routine monitoring of macro invertebrate communities be
                                                                                                                                                   13

 Maximum level            248.1               100     WP982420MC (5)     continued at five-yearly intervals.  This recommendation was
                                                                         accepted by Hawkes Bay Regional Council in October 2009.
                                                                         The next scheduled monitoring will occur in March/April 2014.
TABLE 8 // Design capacities of discharge control points within the WPS.

                      Site                                                                                            Type      Design Capacity l/s        Consent No.
                      Kaitawa tunnels                                                     Discharge g/w and drainage water                      80         DP982020W
                      Kaitawa weir drains                                                 Discharge to Waikaretaheke River                     100         DP982111W
                      Kaitawa Power Station penstock main inlet valve                       Discharge to unnamed tributary                     700         DP982114W
                      Kaitawa Power Station tailrace                                                       Take for cooling                    110          WP982113T
                      Tuai Power Station                                                                         Discharge                      10         DP982220W
                      Waikaretaheke Diversion Canal                                       Discharge to Waikaretaheke River                     100         DP982323W
                      Piripaua Power Station cooling circuits and penstocks               Discharge to Waikaretaheke River                     100         DP982512W
                      Piripaua Power Station oil interceptor                              Discharge to Waikaretaheke River                      15         DP982515W
                      Piripaua Power Station tailrace                                                      Take for cooling                    110          WP982511T
                      Piripaua Tunnel large siphon                                        Discharge to Waikaretaheke River                     200         DP982501W
                      Piripaua Tunnel small siphon                                 Discharge to an unnamed tributary of the                    150         DP982503W
                                                                                                      Waikaretaheke River
                      Tuai Outdoor Switchyard cooling water system                       Discharge to an unnamed tributary                      11         DP982403W
                      Tuai Power Station cooling water system                              Discharge to Lake Whakamarino                       100         DP982412W
                      Tuai Power Station oil interceptors                                  Discharge to Lake Whakamarino                        20         DP982413W
                      Tuai Outdoor Switchyard cooling water system No.1                  Discharge to Kahutangaroa Stream                       1.4        DP982414W
                      Tuai auxiliary turbines                                              Discharge to Lake Whakamarino                       400         DP982415W

                     4.2.2 WAIKARETAHEKE RIVER ECOLOGICAL                                          The high quality of the in-stream habitat and predominance of EPT
                     ASSESSMENT BELOW PIRIPAUA                                                     taxa are likely to be key factors in the river supporting a healthy
                                                                                                   trout population, with an excess of 100 medium to large trout per
                     In addition to the macro-invertebrate monitoring described above              kilometre recorded by Fish & Game in October 2008 (Osborne, 2009).
                     in 4.2.1, Genesis Energy commissioned Freshwater Solutions
                     Ltd to undertake further investigations into the ecology of the               4.2.3 WAIKARETAHEKE RIVER TROUT
                     Waikaretaheke River below Piripaua Power Station.  This work was
                     aimed at gaining a better understanding of the ecological system              Between 1999 and 2001, trout populations in the Waikaretaheke
                     that has developed in the 4 km section of river below the power               River were monitored by twice-yearly drift dives (May and
                     station under the current flow regime. Initial assessments were               September) to determine whether recreational flow releases were
                     conducted in summer (February 2012), and further comparative                  impacting on trout numbers (Kusabs, 2002). The study found that:
                     assessments were undertaken during the reporting period in
                                                                                                       the Waikaretaheke River below Piripaua supported moderate
                     winter (August 2012). The results are reported by Freshwater
                                                                                                       densities of rainbow trout and low numbers of brown trout;
                     Solutions Ltd (Montgomerie, 2012).
                                                                                                       recreational flow releases did not adversely affect trout
                     The flow regime on the Waikaretaheke River below Piripaua Power                   abundance in the upper Waikaretaheke River.
                     Station results in a variable flow ranging, potentially, between
                                                                                                   Kusabs (2002) stated, however, that the long-term effects of the
                     1 and 45 m³/s and, typically, between 5 and 40 m³/s daily.  This
                                                                                                   flow releases on the trout population would only become apparent
                     section of river has a moderate gradient, is willow lined and
                                                                                                   after 1 to 2 generations (3–6 years for rainbow trout and 4–8 years
                     bouldery in nature.  The riverbed is typically 20 m wide with a
                                                                                                   for brown trout). Consequently, the Waikaretaheke River Monitoring
                     permanently wetted channel of 15 – 18 m and a variable (temporal)
                                                                                                   Plan recommends that five-yearly drift dives be carried out.
                     wetted zone typically of 1 to 3 m on each side of this permanently
                                                                                                   Lake Whakamarino  HBRC WP982420Mc (9)
                     wetted channel. The channel is generally “U” shaped with most
                                                                                                   Piripaua Power Station  HBRC DP982510Wb (11)
                     additional flow accommodated by an increase in water level
                                                                                                   Waikaretaheke River  HBRC WP982320Mf (13)
                     rather than an increase in river width.  The dense willow habitat
                     that lines the river bank traps sediment and has allowed native               The last five-yearly drift dive survey of trout in the Waikaretaheke
                     charophyte communities to establish, creating a very stable river             River was undertaken in October 2008, in line with the
                     bank environment in the variable wetted zone.  Willows play an                recommendations of Kusabs (2002).  The next survey is scheduled
                     important role in stabilising and shading the river in a landscape/           for October 2013.
                     geology that is highly prone to erosion and sediment runoff.
WAIKAREMOANA // 13

                                                                                                   4.2.4 TUNA (EEL) MIGRATION PROGRAMMES
                     The results of ecological assessments in both summer and winter
                     show that the Waikaretaheke River below Piripaua Power Station                In 1996 Strickland recognised the potential for improving the
                     supports diverse and high quality in-stream habitat; abundant                 upstream passage of tuna (eels) within the Waikaretaheke
                     periphyton growths in permanently wetted areas that did exceed                catchment.  From this finding, an elver catch and transfer
                     Ministry for the Environment (MfE) guidelines in summer but not               programme began in 1996/97 with the installation of a trap
                     in winter; and low periphyton cover and biomass within the varial             immediately downstream of Piripaua Power Station.
                     zone in both summer and winter. Results show that the benthic
                     invertebrate community within permanently wetted areas is                     In addition to this, a Tuna Fisheries Management Plan was
                     characterised by low diversity (total taxa number); moderate to               developed for the Waikaremoana area following a tuna
                     high % Ephemeroptera, Plecoptera, and Trichoptera (EPT) (though               workshop held in Tuai in January 2008, where members of the
                     low total EPT taxa number) in both summer and winter; low                     Waikaremoana community expressed concerns for their tuna
                     Quantitative Macro-invertebrate Community Index (QMCI) scores                 resource and a desire for the development of such a plan.  The
                     in summer and moderate to high QMCI scores in winter. Overall                 Lake Waikaremoana Hapu Restoration Trust (LWHRT) were
                     the benthic invertebrate indices scores seemed to be strongly                 contracted to assist Genesis Energy to prepare this document with
                                                                                                   input from NIWA.  A number of hui were held to help scope the
14

                     influenced by periphyton cover and biomass.
                                                                                                   plan, seek input from stakeholders and provide training for local
                                                                                                   tuna fishers on key issues.
You can also read