OUPUC~)E

o1 ~&M3 2005 1----:-:--:-----... -.... --....; Ministry of Justice Wai 1200 #1 35 WELLINGTON

Lake Taupo Hydrology Review

A Report Prepared for the Waitangi Tribunal

July 2005

Drawn on 25-Jul-2005 10: 357.6 La e Taupo Lake Lev I Full Record

357.4

357.2

357.0

356.8

356.6

356.4 r­ III '"~ 356.2 III c: 15 356.0 r­ III ~ 355.8 r- ~ 1906 1926 1946 1966 1986 ~ 3 -- 82795 from 13-Jul-1905 00:00:00 to 09-Jun-2005 06:00:00

David Hamilton David Hamilton & Associates Ltd Consulting Engineers POBox 1420 Dunedin

Phone: 64 3 454 3380 Fax: 64 3 454 3292 Mobile: 021 338555 Email: [email protected]

David Hamilton & Associates Ltd Page 1 of61 1 August 2005 Lake Taupo Review

Preface

This report has been prepared by David John Hamilton. My academic qualifications are Bachelor of Engineering (Hons) (Agricultural) from the University of Canterbury and a post-graduate certificate in Engineering Hydrology from the University of New South Wales. I am the Principal of David Hamilton & Associates Ltd, a consulting engineering company based in Dunedin.

I am a Fellow of the Institution of Professional Engineers New Zealand. I am a member of the International Water Resources Association, New Zealand Society on Large Dams, the New Zealand Hydrological Society and the NZ Institute of Agricultural and Horticultural Science. c

I have worked in river and flood control, irrigation, engineering hydrology and water resources for 34 years. This work has included irrigation investigation, design and construction on the Lower Waitaki Irrigation Scheme (1969-1977) with the Ministry of Works & Development, 2 years as a water supply engineer in Apia Western Samoa (1977-1979), 4 years as Deputy Chief and then Chief Engineer at the Hawkes Bay Catchment Board (1979-1983), 6 years as Chief Engineer of the Otago Catchment Board (1983-1989), and 8 years as Director of Operations/Director Technical Services with the Otago Regional Council (1989-1997).

I now operate my own consulting firm and act as a specialist consultant, in the natural C resource engineering area, based on my experience, to a range of public and private clients.

Acknowledgements Data from NIW A and Opus was sourced with approvals from Genesis Power, Mighty River Power, Contact Energy and M-Co who are part funders for the hydrological information.

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1. Introduction The review of hydrology relating to Lake Taupo has been prepared at the request of the Waitangi Tribunal. This review does show that the average lake level since the control gates were commissioned in 1941 has been just under 50mm higher than the pre-control recorded mean. The maximum level since 1941 has not reached the natural recorded leveL The current mode of operation is now relatively close to the natural lake level fluctuation without reaching the very high levels. There was however a period during the 1940s and 1950s when the lake was operated at significantly higher levels for extended periods.

Lake Taupo is a large lake in a basin that was formed by volcanic eruption. The area is still active tectonically. The catchment area has been subject to changes in land cover through the action of nature and the actions of people.

Hydroelectric power development saw the construction of outlet control gates in 1941 and the diversion of headwaters of the Whanganui and Rangitikei Rivers through the Tongariro Power Development in the 1970s.

This report aims to provide an audit of the evidence provided to the Tribunal concerning the impacts, if any, of the control of the level of Lake Taupo from the time of establishment of the control gates to the present. Impacts on adjacent lands and waterways are included. In order to do this source material and data relied on have been reviewed.

In order to assess the changes that have occurred through the introduction of hydro­ electric facilities at the lake outlet and affecting the catchment, it is important to also understand the nature of other factors that may have impacted over the same time.

2. Catchment

2.1 Area

The Lake Taupo natural catchment is 3289 km2 in area. This is the upper part of the Waikato River catchment that has a total area of 14,258 km2 and is the largest in the

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North Island. The Lake Taupo catchment drains parts of the Volcanic Plateau from Ruapehu (2797m asl), Tongariro (1967m asl) and Ngaruhoe (2287m asl) as well as the Kaimanawa Ranges (generally 1500-1600m asl), and the eastern slopes of the Hauhungaroa Ranges (generally 800-900m asl) (Purerora Forest Park).

The average lake level is RL 356.7m above mean sea level (Moturiki datum).

2.2 Lake

Lake Taupo was formed by a major eruption about 22,000 years ago, the Oranui Eruption [Hancox, #H31, paras 4.4-4.8]. The Taupo Eruption of 181 AD emptied Lake Taupo and deposited Taupo Pumice Ignimbrite radially around the vent. After

this eruption Lake Taupo refilled to about 34m above present lake level (~390m). . This developed a high alluvial terrace. The Waikato River scoured the barrier outlet ( about 30 years after the eruption and released a large flood down the Waikato River.

Lake Taupo's surface area is 611 km2 or 18.6% of the overall Lake Taupo natural catchment area. This is a high proportion of lake area to catchment area. As a result the lake has large balancing influence through: • Reduction of flood peak flows through the lake storage slowing down the rate of outflow • Maintaining higher outflows when inflows are low.

These characteristics are common to most large lakes but the high proportion of the catchment as lake means that these characteristics are amplified or more significant for Lake Taupo, and can occur over a relatively small range of water levels. (

The minimum lake level on record (1905-200S) is 35S.772m and the maximum lake level on the continuous record is 357.723m, giving an overall range of 1.951m or just under 2.0 metres.

Based on average flows the lake has a volume equal to 13.S years of flow under natural conditions. This same volume now equates to about 10.S years including the additional Tongariro Power Development diverted water. The active volume over 2 the last 100 years is the surface area times the operating range or 611 km x 1.951 =

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3 1192 Mm . The normal operating range in terms of the Mighty River Power consents is now 357.25-355.85=1.4m, although flood storage up to 357.387m or greater can be utilised.

2.3 Geology

Hancox [#H31, sections 2 & 3] describes the active Taupo Volcanic Zone that includes volcanism, high crustal heat flow (geothermal and volcanic activity), active normal (extensional or pull apart) faulting and ongoing tectonic deformation, and numerous shallow earthquakes. The ranges of older greywacke rocks border the taupo Volcanic Zone, with the Hauhungaroa Range located to the west, and the Kaimanawa Mountains to the east. There are many volcanic deposits in the catchment that are soft and unconsolidated. These deposits include pumice gravels and breccias derived from the 181 AD Taupo eruption. Brown ash and pumice \ gravels have also been derived from Mt Ruapehu and Mt Ngaruhoe in the upper catchment area.

·2.4 Soils

As there is very little clay in the soil parent materials to provide cohesiveness, the pumice and ash soils are extremely fragile and prone to severe gully, sheet, rill, . streambank and wind erosion.

2.5 Land Cover

Figure 2.1 shows the land use within the total catchment area of lake Taupo including the lake area. This data is sourced from Environment Waikato. Indigenous forest at 21 % is larger than the lake area (18%), pasture (17%) or plantation forest (17%). The changes in land use since 1840 are presented in the next section.

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Bare ground/lava/quarry 4% Tussock Urban Settlement 5% 5% Wetland 1%

Indigenous forest 21%

Scrub/shrubland 12% ( 18%

Planted forest 17%

Figure 2.1: Laud Use Taupo Catchmeut (2000)

2.6 Rainfall

The seasonal pattern of rainfall is shown as Figure 2.2. This is copied from Figure 4.2, "Waikato Catchment Hydrological Overview" prepared for Mighty River Power Ltd by NIWA and Opus, May 1999. These show average rainfall as generally higher in the winter. High monthly totals can however occur at any time of year. (

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60.0 s.oo e ~oo ! ':iiio · : : f: . : . :': : :{::.' : : :: : :. ': : : t' : : :1:" : . :t: .: : :: ::f: . 'if I'~" , "1',0, :~:: , .' . ·c or.; 200 ...... ••·.·.C •••••••••.•.•• ·: •••••• ' .•• , ...... ~ · .....•.••.• : •.~ .... , .••.••.•.••.•...• ,••••...• "! ••. '. 100 . . ,.. ',10 10 () Jan feb Mar Apr May Joo Jtil. Aug Scp Oct Nov Dec

(i) Mt.Ruapehu, Chateau.(C9.5152); p'eriod: 3/9/Si to 3'111/98

900 800 · ...... • '" • - - , . - , - - •. , .. " •.. , - , • , ,. , , •. , 'r"' , - .. - - - , , 70.0 ...... " ...... ", ...... ; .... - ...... , ......

E 600 ...... ' ...... ".... -" ...... " ...... ! 500 ·3 40.0 '. r' , •.•.•• - ..• , • , , ....••• 't. ' ., ... i<' , , ' .• , .. , , •• , , , , . , .::<: 300 ~ ~ 'f .- ...... ,. '" I- ,... ,- 'f' ..... 200 , .... ". .. -I ', 10.0 ~ ::: :::;:::::::: : : : : ; : : : ~:: ::::::::::::: : : : : 0 • • .' , .., 1 , , • • Jan Feb Mar Apr May lun Jul Aug Sop Oct Nov Dec

(ii) Tongariro Hatchery (C9S0B1), Period:. 3/4129 to 3111/98

250

2.00 , . • ...... r, . , . . , . . , ...... r' • . . , • • . • . . . r', • • • .. . . , .. E 3 150 :§ 10.0 'r" 'r' ...... ,.. '1' . e: ...... I····'· .I' ...... or; ~ 50 ••.••••• :::::1:1::·::: ::::: :::I::. 0 • 10 • .•••• Jan Feb Mar Al'f May Joo lui Aug Scp Oct 'Nov Dec

(iii) RlIinbowPoirit (BB6703), Period: 3/9/78 to 3111/98

Figure 4;2 Waikato Catchment ~ Minimum, Mean and Maximum Monthly Rainfall

Figure 2.2: Monthly Rainfalls at Chateau, Tongariro Hatchery ) and Rainbow Point 2.7 Wind

Data is available for the daily wind run at Taupo Airport. Figure 2.3 shows the seasonal wind run. The westerly component is the main wind direction. This is strongest in the spring (September-November). This information is useful in assisting the understanding of shoreline erosion.

David Hamilton & Associates Ltd Page 7 of 61 1 August 2005 t1 WarIAprMay ~ JunolJUlylAug 0: Sftc 867004 Windspeild &.dlrtnatTaupo AWS ::c Site 8671i04 WlIid sPeoo &. dlrtnai Taupo AWS 31-Oc.I-199i Itl 19:-Oct-1999 31-OcI'I991·i()1~0c1-1999 @. mrs R3rcent m's R3rcent 8'::: 10.1 + f/? 10;1 + 5.1-10.0 >-CIl 5.1-10:0 CIl 25 o ~ 2.1-5.0 20 (l ..... 2.1-5.0 20 p;' (J'C:l 15 1.1-2.0 ~~15 @" '"'l ~E10 1.1-2:0 CIl = 10 ('I) Calm 5 ·5 t-< N 0 Calm a W 0

r:JJ. ('I) ~ oI:I.l [)!clJanIFeb '"C1 =~ SeptlOcfJllbv :fci - Sae 867004 Wind,speed &: dlrtn atTaupo AWS (t> .....~ Site. 8670MWlrid speed & dir1n al TaupO AWS 00 31-Oct-1991 to 19-Oct-I999 =Q.. m's R3rcent ·31-Oct-I991 tolg.()cI-1999 g, riYs R3rcent 0\ ...... ~ 10.1+ 10.1+ = 5.1-10.0 a ! .5,1-10.0 >-3 2.1-5.0 20 ~ . 15 2.1-5.0 ·.E 1.1-2.0 15 ~E10 1;1-2.0 '"0= 10 o Calm 5 0 ~ Calm 5 > o o ~ ~ r:JJ.

Figure 3~1"2: Seasonal wind roses for Taupo AWS .. ('I>~ ~ :::>- {Jq ,§ ::: o ~ ::0 1:5o ~. l.Il ~

/"--:--', 1--\ Lake Taupo Review

3. Land Use

3.1 Changes in Land Use

An assessment of land use change was undertaken by Environment Waikato. The situation in 2000 is presented above (Figure 2.1) as a pie chart and as a map in Figure 3.2. The change in land cover from 1840 to 2000 is shown in Figure 3.1 and Table 3.1.

180,000

160,000

140,000

120,

100,000

80,000

60,000

40,000 lllI Landcover 1840J 20,000 [;] Landcover 2000 o

"0 c: Landcover 2000 10 .... :0 VI ::l 2 o .c: ~ c: VI "0 OJ J:r c: 0> 2 10 =a u :s oS Vl

Figure 3.1: Land use chauges 1840 to 2000 for Lake Taupo catchment

( Lake Taupo Catchment Land Cover ex Environment Waikato Areas in hectares Percentage Description Landcover 1840 Landcover 2000 Change Urban Settlement - 16,308 Indigenous forest 89622 77,429 -14% Scrub/shrubland 14637 44,540 204% Planted forest - 61,939 Inland Water 63759 64,015 Pasture - 61,947 Wetland - 1848 Tussock 177744 18,000 -90% Bare ground/lava/debris flows/mine/quarry 1479 14,849 904% Totals 347241 360875 Table 3.1: Land use changes 1840 to 2000 for Lake Taupo catchment

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Barel:lr:ourid

.E Ho!ll.-ultUral

• indlgtnous FORlst

l1li, Inland Water

Inl.nd WeUlInd

Planttd Forest

Scrub

Urban

(

(

.. . Lake Taupo - Land CoVer January 2001

Scale 1: 47Q 000

Figure 3.2: Land Use Taupo catchment 2000

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The most significant changes are the conversion of tussock country to pasture, plantation forestry and scrub and shrubland. There is also a reduction in the area of indigenous forest and the establishment of the urban areas.

3.2 Local influences

There are a number of human activities that impact at a local level in addition to the major TPD works and the outlet control gate structure. These include: • Land use and land use practices • Hydro-electric power facilities • Waste, wastewater and stormwater management • Utilities - roading, energy and communications network impacts • River, flood control, gravel extraction and land drainage works

( • Urbanisation and channelling of stormwater • Shore protection and boat ramps

There are a number of natural factors that affect the natural processes at a particular site: such matters include the topography, geology, soil type, aspect, slope, rainfall intensity and rainfall duration. Also such matters as volcanic ash deposition or climate change affecting sedimentation or floods or droughts are factors influencing local impacts.

Changing land uses can affect the peak flood flow and total volume of runoff. Generally the more intensive the land use at a site, the greater the runoff - native bush, plantation forests, and wetlands have the lowest storm runoff and tussock country will have greater runoff than bush or plantation forest. Developed pasture has significantly greater runoff than the first categories, whilst urban land - either residential or industrial and commercial land has the greatest volume of storm runoff per unit area.

The duration of flooding on a property may also be significant. Depending on the time of year and water temperatures, pasture may die after 3 days of inundation.

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Drainage of Peat land

The drainage of the peat lands has resulted in settlement of areas in other parts of the Waikato. The extent and nature of peat lands that have been drained is not known but land drainage works were undertaken in the southern Lake Taupo area prior to the control gates being commissioned [Walzl, #EI]. Rates of peat settlement averaging 4.5mm per year were recorded in the Pouarua Block on the Hauraki Plains (Acheson, p223).

4. Hydro-Electric Developments

4.1 Introduction

The Government constructed its first hydroelectric dam on the Waikato River in 1929 at Arapuni and subsequently constructed a further seven hydroelectric generation ( stations, plus control gates at the outlet of Lake Taupo. Between 1967 and 1979 the Tongariro Power Development (TPD) was constructed. More detail on these developments is given below.

4.2 Outlet Control Works 1941

The outlet control works were commissioned in September 1941 [Freestone #H29 para 10.14]. Walzl [#El, para 120] states "At sometime in October they were opened for the first time." The lake control gate structure was constructed in the dry within a new channel to the east of the old river channel. The control structure is 1 km

(

Figure 4.1: Taupo Control Gates Photo from Mighty River Power Taupo Waikato Resource Consents Project ABE Discussion Draft Nov 2000, Figure 4.1

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downstream of the lake and State Highway 1 uses the structure to cross the Waikato River. Associated with this structure was the deepening of the outlet channel and the removal of various rock bars to improve the outflow at lower lake levels.

The intent of the works was to regulate the outflows. This would allow the storage of the spring and summer runoff for use in hydroelectric production the following winter. The gates also permitted the outflows to be adjusted to suit daily hydroelectric operation for the sites on the Waikato River. There are six vertical concrete gates, each able to be remotely controlled. The sill invert level is 351.90m and the structure crest level is given as 361.50m

levels m,o T (melr.,) -361.50 Slructure Crest. Level

36C6 +

I------''----~--, ~ 357.387 Statutory "Flood. Level ~o,. ,Cl Apr-Oec ::2',0 j1 -,_J~ii5 Max. CL Jan-Iolor ;,6.0 -355.85 Minimum' Control leyeJ

35'0 Six Cotes each 4.. 57m ~ide :::.: I 1-:-:-:-...---,:-~!:7;::;;=:;:=.==:::::t!=~~::;::clR-:--~---:--;-'-'-: -' 351.90 5i11 lev.I(Gole L.vel)

Figure 4.1: Key Levels for Lake Taupo and Taupo Control Structure Fig 4.2: Cross section Lake Taupo Control Structure from "Lake Taupo and Waikato River Levels and Flows" Mighty River Power Contract ( C98115, NIWA & OPUS, Section 4.1, Figure 4.1

A major change was thus the ability to release much larger flows under low lake conditions than could happen before the control gates and associated works were in existence. Prior to the gates an increase in outflow had to be accompanied by a rise in lake level.

The pre-1941 rating curve (a plot of flow versus lake level) is shown as the top graph line in Figure 4.3. The lower line represents the control gate in place but with all gates open.

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359

358

357 7ico -S Q3 :> 356 ~ Q,) ;.!Gco ....J 355

-~- Unmodified Channel Rating 354 -1'1I-NbConsenls Rating

353 • • • 50 100 150 200 250 300 Flow (m3ts)

Figure 10.10: Lake Taupo unmodified channel and "no consents· outflow ratings. (

Figure 4.3: Lake Taupo Outflow ratings for pre-1941 and all gates open (no consents) derived from #H29, Figure 10.10

This shows that for a level of 356m the outflow can now be up to 180m3/s compared with pre-1941 of about 70 m3/s. Similarly for a level of 356.7m, the median lake level, the flows are about 250 m3/s and 120 m3/s respectively. This increase in outflow at a given level is very significant for the management of the lake level as well as the ability to supply peak load flows for the hydro-electric stations downstream. The maximum outflow capacity of the Taupo gates is about 315 m3/s [Webby, #H30, para 8.5]. ( The gate operation results in fluctuations in the flow of the Waikato River to match hydro-electric generation requirements. Figure 4.4 shows the Waikato River at Reids Farm flow for a 27 day period in January-February 2005 that demonstrates the way the outlet flow is adjusted to match the hydroelectric generation requirements. Flows varied between 60 m3/s and 280 m3/s. Under the pre-1941 situation the flow would have been relatively constant for a lake level between 357.015 and 356.90m at between 150 and 165 m3/s.

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Waikato River at Reids Farm Drawn on 25-Jul-2005 10: 300

250

200 J n

150 ~

CJw· e> ::T 100 III «3 Iv

-1 25-Jan-2005 30-Jan-2005 4-Feb-2005 9-Feb-2005 14-Feb-2005 19-Feb-2005 --- 1143444 from 24-Jan-2005 14:05:07 to 20-Feb-2005 15:12:30

Figure 4.4: Waikato River at Reids Farm flow variations (NIW A)

Figure 4.5 shows the outflows for a six month period in 1933 showing the slow increase with lake level and slow fall.

Lake Taupo Outflow June-December 1933

200

180

160 .-/ -...... /

140 ~

~ 120 / ----- M E V ~ 100 o S o" 80

60

40

20

o 12-Jun-33 12-Jul-33 ll-Aug-33 10-Sep-33 10-0ct-33 09-Nov-33 09-0ec-33 Figure 4.5: Lake Taupo Outflow variations pre control gates

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4.3 Lake Taupo Compensation Claims Act

In 1947 the Lake Taupo Compensation Claims Act [#E52] was passed and set a maximum control level of 1177 ft (357.387m Moturiki datum) as the level above which compensation could be claimed if this level was exceeded for generation purposes.

The 1947 Act was amended in 1976 and changed the terminology to "Maximum working level". The level is referenced to the Taupo fundamental benchmark near the Lake outlet. Special claims for compensation are able to be made if the works are used for the purpose of controlling the waters of Lake Taupo at levels higher than the maximum working level.

Freestone [#H29] notes in para 10.15 that following a report in 1968 on the seasonal ( occurrence of floods an operational seasonal maximum control level was introduced. The report had concluded that the largest floods in the Waikato River catchment tend to occur in the months of January to March. The operational maximum levels were set at 1176.5 ft (rounded to 357.25m) from April to December and lowered to 1176 ft (rounded to 357. 10m) from January to March. More recent studies for the Mighty River Power consents using additional years of record concluded that these seasonal rules were unnecessary and this has been reflected in the consents as granted. The current consent has a maximum control level for the purpose of water storage for hydro electricity of 357.25masl and a minimum control level of 355.85masl [#H28].

4.4 Tongariro Power Development ( Diversions of water from other catchments into the Waikato catchment occurs as part of the Tongariro Power Development now operated by Genesis Power. The western diversion was commissioned in February 1971 and the eastern diversion was commissioned in October 1979. The water from both diversions passes through Tokaanu power station into the southern end of Lake Taupo.

Extra water is introduced throughout the year. Although provision is made for these diversions to cease when the Lake Taupo level reaches or is likely to reach the maximum control level, the additional water has a number of downstream effects:

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• An increase in the fluctuations of flow in the Tongariro River system affected by the TPD • A possible reduction in flood storage within Lake Taupo • An increase in the rate of outflow from Lake Taupo • An increase in the range and rate of fluctuations of flow out of Lake Taupo • An increase in the generation from the hydro electric stations on the Waikato River • An increase in the mean flow of the Waikato River • A possible increase in the flood flows in the Waikato River • An increase in the low flow of the Waikato River

3 ( At mean flow the TPD diversions add 30.8 m /s (1980 to 2001) which represents an increase of 24% in the natural inflow to Lake Taupo. This TPD inflow now represents 19% of the total Lake Taupo inflow on average. [Freestone #H29, para 8.3- 8.4]. Table 4.1 shows flow figures for 1980 to 2001.

Flow parameter TPD total diversions Flow m 3/s Maximum instantaneous flow diversion 69.0 Maximum daily average diversion 63.5 90% of time flows less than 45.6 50% of time flows less than 32.1 10% of time flows less than 13.5 \. Minimum flow 0 Table 4.1: Flows for period Jan 1980 to Dec 2001 [Freestone #H29, Para 8.5-8.6]

Minimum flow requirements imposed on the Whakapapa and Whanganui River intakes in 1992 are likely to reduce these averages.

Smart [#H2(b)], in his Executive Summary, states that the "Tongariro is a volatile river which undergoes significant channel changes in response to floods and eruptions. The river transports vast amounts of sediment through its upper reaches

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and deposits the sediment on its delta from Turangi downstream." He states that "the dominant factors influencing the growth of the lower delta have been the frequency and magnitude of floods and eruptions, the level of Lake Taupo during floods and willow tree growth on the delta. The effects these factors have had on the delta building process can be considered either beneficial or detrimental depending on whether one is considering wildlife habitat or human infrastructure on the delta."

4.5 Waikato Power Development Flood Management Rules

The Waikato Power Development Flood Management Rules (Flood Rules) were developed between the operators of the hydropower system and the Waikato Valley Authority (Environment Waikato) and used since 1975. They are designed to protect the safety of the dams and other hydraulic structures within the Waikato River, and if possible as a secondary objective, to provide for downstream flood relief.

4.6 Tongariro Offset Works Agreement (1977)

This agreement contained flood management provisions requiring "the cessation of "foreign water" diversions from the TPD into Lake Taupo whenever the lake's maximum control level [in terms of the 1947 Act] is reached or is clearly likely to be reached."

5. Lake Records

5.1 Type of Records

Lake level and flow records commenced in 1905 at Taupo. There is thus now just over 100 years of record. This is the longest hydrological record for a lake or river in New Zealand. The outflow is also measured at Reid's Farm downstream of the lake outlet.

Opus have unadjusted and adjusted level records. They have also calculated a total lake inflow record for the period of lake level records. This has been done based on known outflows and changes in the lake level representing so much volume for the day and converted to average flow.

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The hydrological site records were obtained through NIWA and Opus. The clearance to obtain the data for this report was given by those assisting with the funding, being M-Co, Mighty River Power, Contact Energy Ltd, and Genesis. This basic data has been used in this report to check certain key findings in other evidence and to extend the record to June 2005.

The sites for which data was obtained are shown in Table 5.1.

Site No Site Name Period of Source Record 1543478 Lake Taupo at Acacia Bay 1978-2005 NIWA 1143420 Lake Taupo at Tokaanu 1967-2005 NIWA ( 82795 Lake Taupo 1905-2005 Opus 2790 Lake Taupo inflows (derived) 1905-2005 Opus 1143444 Waikato River at Reid's Farm 1969-2005 NIWA Table 5.1: Hydrological Site Summary

5.2 Lake Inflows

Figure 5.1 shows the calculated daily mean inflows to Lake Taupo.

1000 Drawn on 900

800

700

) 600

500

400 r III ",. CD o;l 300 c: -0 0 :;- :=!> 200 ::;:0 Ul 100

0 1906 1926 1946 1966 1986 2790 from 15-Jul-1905 00:00:00 to 09-Jun-2005 00:00:00 Figure 5.1: Lake Taupo Inflows

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5.3 Lake Level

The Lake Taupo water level record (Site 82795) relies on records taken at a number of sites at various points around the lake over the 100 years. See Freestone [#H29, Table 10.1] for details.

I Full Record 357.6

357.4

357.2

357.0

356.8

356.6 ( 356.4 r- Ql '"CD 356.2 s:::mJ "0 0 356.0 ..Ql '"CD 355.8 r- CD < 1906 1926 1946 1966 1986 ~ 3 --- 82795 from 13-Jul-1905 00:00:00 to 09-Jun-2005 06:00:00 . Figure 5.2: Full Lake Taupo lake level record

Table 5.2 levels are taken from H29 paras 10.5 and 10.6 and show the natural and design lake level ranges based on the 1905 to 1941 (pre control gates) data.

1905-1941 Lake Level Range Feet Metres Recorded Maximum 1178.1 357.723 Design Maximum 1177 357.387 Recorded Minimum 1172.3 355.955 Design Minimum 1172 355.850 Actual recorded lake level range 5.8 1.768 Design lake level range 5 1.537 Table 5.2: Lake Taupo Pre-Control gates levels in terms of Moturiki datum

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The highest sustained period of lake level was that during World War II and predating the setting of a maximum control level MeL in 1947. Figure 5.3 shows the lake level plot for this period.

Max Lake Taupo Lake Level 1941-1947 Drawn on 27-Jul-2005 16: 357.6

357.4 MaxCL

357.2

357.0

356.8 100 yr Mean r- 356.6 OJ @ !; 356.4 ~ 3 356.2

356.0 ------_____ MinCL 355.8 1942 1944 1946 --82795 from 01-Sep-1941 00:00:00 to 01-Sep-1947 00:00:00 Figure 5.3: Lake Taupo lake levels 1941 to 1947

The peak daily inflow into Lake Taupo was recorded in February 1958 at 1357 m3/s. The peak recorded outflow from the lake is 315 m3/s. The natural lake storage is significant even without the control gates .. The storage and outflows are now manipulated by use of the control gates.

5.4 Seasonal lake Levels Figure 5.4 shows the monthly mean lake levels for 1905 to 1941 (pre control gates). Figure 5.5 shows the same parameters for 1941-2005 (post control gates). These show the rise in winter and spring and dropping off to a winter low. Figure 5.6 shows the plot of the monthly means for the pre control gate, post control gate and the period from 1941 to 1947 after the control gates were commissioned until the maximum control level was set. This clearly shows the average levels in December -April being higher than the natural situation by an average of about O.lm. This graph also shows

David Hamilton & Associates Ltd Page 21 of61 1 August 2005 Lake Taupo Review that over the 1941-47 period the average lake levels were about 0.3 to 0.5 m higher than the pre-control record.

Lake Taupo Monthly Mean Levels 1905·1941 358r------,

357.5 f------_--==--...... :...... ------=---I ",--- /- ----...... -.------,/ --...., /' 3~+_------~~-~~------~- - .::l 356.5 t------=""--~--....",==------____I ~ .5 ------.,.------...... _------.... 3~+_------~-~-~----~-~------_I-----

355.5 +_------1 (

355+---~~-~---~---~----~--~---~----~--~-~---~---~ Jan Feb Mar Apr May Jun Jul Aug Sep oct Nov Dec Figure 5.4: Lake Taupo Monthly Levels 1905-1941 (Pre control gates)

Lake Taupo Monthly Mean Lake Levels 1941·2005

358r------~

357.5 +--_;::------".--"------==------...-:----__1 ...... ----- ",.... -- ...... - -- 357+_------~

E ] !l 356.51------~::::::::::=====:::::::=------_1 ~ .5 -- ...... -- ( 356+------~-~~------~------~------__I--- -...... ------.. _----_ ......

355.5 +_------~

355+---~_--~----~----~----~--~---~----~----~-~---~----~ Jan Feb Mar Apr May Jun Jul Aug Sep oct Nov Dec Figure 5.5: Lake Taupo Monthly Levels 1941-2005 (Post control gates)

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Lake Taupo Monthly Mean Lake Levels

358

357.75

357.5

. ~ ~ ~ ...... ~ .. -_. -----. --. -. ------. _. _.. ------_. -. _. _. _. ----... -. ---. - /':'*:- ~ .-:-:-:: ~ --=-.. . - 357.25 ...... _/ 357 ...... ~ ...... -~ ...... - """"--,... -ii!! E 356.75 •• 11lJ:..;...... ~ • .,..,..,--• ../...... - iii- ir----, 'iii - ilil- -m-- 1905- ....~ 356.5 ...... '''''''ili!'-'- 1941 .el --1941- III .... 356.25 1947 --+--1941- 356 2005

355.75

355.5

355.25 ( " 355 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Figure 5.6: Lake Taupo Monthly Mean Lake Levels Pre-control, Post control and 1941-1947

5.5 Seiching

Wind induced set up can result in the downwind shore having a slightly higher water surface than the upwind shore. When the wind drops the lake surface experiences a seesaw oscillation that is eventually damped out by friction at the lake bed. Such oscillations are termed a "seiche". Freestone [H29 para 10.31] states "The predominant oscillations observed on Lake Taupo are a north-south oscillation with a period of about 35 minutes. Measured seiche amplitudes are typically of the order of () 10mm to 20mm." He also states that the phenomena is unaffected by lake control.

5.6 Simulated Natural Lake Level

In Mighty River Power Taupo Waikato Resource Consents Project ABE Discussion Draft page 113 a series of graphs comparing the actual lake record with a simulated natural lake record is produced. The simulated record assumes that there are no TPD diversion inputs and that the outlet channel had not been enlarged in 1941. This is shown as Figure 5.7 [#E52(a) also includes these graphs].

David Hamilton & Associates Ltd Page 23 of 61 1 August 2005 o ~ Figure 6.19 - Lake Taupo levelshowihg:the uncontrolled level since 1905. (simulated after 1941)andt/)e~controlledleve/sincef94J 0.: ::r: 358 ~ -.~ 8' (JC) !:l 357 ="'! Ro ('t) ;J> Ul 356 en oen ~ ;;;.(') ('J:l_. 355 'OhJAN-OS ~AN-08 ~N-11 ~AN,14- ~N-17 ~N-20 '.J,6;tf23 ~ 3 358 l' = S. -~ '*('t) 357 Q.. t"'I 356 ~ ~ I G~ta~Coiltrl)/_:;;;_ ('t) 355 I .. ~. '"tI t"'I 01.JAN-25 !JAN-28 !JAN-31 !JAN,,34 ·liAN-37 .~~.. ('t) < 358 ~ ('t) E ~ ,...... ,-I:Il - . -'ii 357 o....., ~_ (JC) a; 0'\ .... 356 ...... ="'! 41) ('t) ii ~ .... ---_... _--- ..... 355 OhJAN-45 ~AN-48 \JAN-51 iJAN-54 \/AN-57 'J,4.N-50 .-:JA~ ~ 358 ~ ~ S 3S7

~ 356 ~ ,.-,~ N 355 - <::> 01.JArM5 !!ArM8 !!AN-71 iJAN-74 iJAN-77 !!AN-SO :J.6.ff8:3. l' <::> <::> I I I I I I '-' ~ '--' >-3

;J> ~ A fl.. A... A ~ M ~~. .~ _M-A. ~ :l~~~ 1 "0 r:g 0 c:: "I- .~ I' ?::1 :'!l. 356 +- V\! V ·ow + ~. l:5o CP Ul 355 I ::E 01.JAN.fl5 ~AN.fl8 !JAN-91 ~AN-94 ~AN-97 !JAN-OO !Jmoa. Lake TaupO COritl:"OlIed level{m)

Lake Ta~ uncontrolled level (m). (simulated after 1941) ~ r "' Lake Taupo Review

The graphs show that immediately after the control gates were commissioned the lake was held at a relatively high level. Through until about 1969 the annual range between maximum and minimum levels was generally greater than would have occurred naturally. Since about 1987 the lake has been operated on a basis that is closer to the natural regime. The simulations of what natural levels would have been had there been no control gates and no TPD flows have not been redone but a review of the methodology confirms that they are a realistic interpretation of what the natural situation would have been.

6. Lake Level Data Interpretation

6.1 General

Freestone [#H29 Section 10] covers Lake Taupo levels and flows in some detail. This section of this report relies on that analysis but incorporates checks through updates using the extra few years of data up to 9 June 2005.

6.2 Lake Level Duration

Lake level duration curves are a good way to compare operating regimes. These graphs show the percentage of time a particular lake level is equalled or below a certain level. They can be prepared for different periods. In this section lake level duration graphs are prepared for the periods shown in Table 6.1. Table 6.1 lists the mean, median, level exceeded 10% of the time and the maximum level for each period. Figure 6.1 shows the plots of lake level duration for these periods. Figure 6.2 shows lake level duration for the months of December to April for these periods ( excluding the 1941-47 period, and Figure 6.3 shows the lake level duration for the months of May to November for the same periods, also excluding the 1941-47 period.

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Period Years Mean Median Level Maximum (Average) Level exceeded Level Level 10% of time Full record 1905 - 2005 356.72 356.707 357.17 357.723 Pre control 1904 - 1941 356.69 356.656 357.12 357.723 gates Post control 1941 - 2005 356.737 356.756 357.21 357.634 gates Post control 1941 - 1947 357.031 357.215 357.39 357.494 gates to Lake Taupo CCAct Last 10 1995-2005 356.664 356.667 357.09 357.493 years Table 6.1: Periods for Lake Level Duration Analysis with Values

357.6 Lake Taupo Le\el Duration CUI\e Full Year

357.4

3572 1941-47

357.0

356.8

356.6 r ru @356.4 r (J) !i 3562 3 356.0 ( 355.8 0 10 20 30 40 50 60 70 80 90 100 -- 82795 fiom 13-Jul-190500:00:00to 9-Jun-200506:00:00 -- 82795 fiom 13-Jul-190500:00:00to 1.Q:;t.1941 00:00:00 -- 82795fi"om 1-CX:t.1941 00:00:0010 9-Jun-200506:00:00 -- 82795 fiom 1-J.m-199500:00:00to 9-Jun-200506:00:00 -- 82795fiom 1.Q:;t.1941 00:00:00 to 1.Q:;t.194700:00:00

Figure 6.1: Lake Level Duration Curve for Full Year and various Periods

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357.6 Lake Taupo Le\elDuration CUI\e December 10 April

357.4

3572

357.0

356.8

356.6 I;) @356.4 [p ~3562 3 356.0 355.8 o 10 20 30 40 50 60 70 80 90 100 --- 82795 fiom 13-Jul-1905 00:00: 0010 9-Jun-200506:00:00 --- 82795 fiom 13-Jul-1905 00:00: 00 to 1.Q;t.1941 00:00:00 --- 827951i'om 1-Oct.1941 00:00:0010 9-Jun-200506:00:00 --- 82795 fiom 1-J.m-199500:00:001o 9-Jun-200506:00:00

Figure 6.2: Lake Level Seasonal Duration Curves for December-April for Various Periods

357.6 Lake Taupo Le\el DUiation CUI\e May to NO\ember

357.4

3572

357.0

356.8

356.6 I;) @356.4 [p ~3562 3 356.0

355.8 o 10 20 30 40 50 60 70 80 90 100 --- 82795 fiom 13.Jul-190500:00:001o 9-Jun-200506:00:00 --- 82795 fiom 13-Jul-190500:00:00to 1.Q;t.1941 00:00:00 --- 827951i'om 1-Oct.1941 00:00:0010 9-Jun-200506:00:00 --- 82795 fiom 1-Jm-199500:00:001o 9-Jun-200506:00:00

Figure 6.3: Lake Level Seasonal Duration Curves for May-November for Various Periods

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This shows that the December to April levels post control gates were markedly higher than pre control gate levels, yet this is not what is now the mode of operation over the last 10 years. Over the last 10 years the lake has operated at or below the pre-control gate lake level distribution for the May to November period (blue line versus red line) in Figure 6.3 and about O.lm above the pre control lake level distribution for most of the December to April period except at the high end (85-100%) where it has not reached the natural maximum levels.

This confirms that the Freestone [#H29] simulation is not unrealistic. Figure 6.4 shows seasonal variation in actual and simulated lake levels from 1992-1998 as presented by Freestone [H29]. This illustrates that over this period the seasonal pattern was similar to the natural situation and peak levels slightly lower. (

( ,) I

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358.0 --.•. ....:..-~..;;,...--'--,.-.-."" ..:...---.....;...-,. _. -,...... ---'--.--.-----~

357.5 .;.----,,----'-

357.0 .-..•. -... -... ~-..... ~.----~

~;5··1------~ -- SlmulatedUIlColllroiled leVe! -". Acll.(al'level

355.0 -1-'-----...;...--,.;----'------...... ,.----,.;.....,.--,.;------4 .0 20 40 60 80 .100 PercentageofTime

Figure 10.4: Duration profilesfortheact(W~nd slmuiated uncolitrolledlevel of Lake Taupo, from January 199110 Febrilaiy 1998.

358.0

3575

357.0 g g;! 356,5 <1l -l

... ~".~=.~ ActLal·mean 355.5 .... -----.---.---.-.----.--. ... -.- Actual rilaximum I minimum ---- Simulated unconlrolled mean -- Simulated unconlrolled maximum! minimum

Jan Feb Mar .Apr May Jun Jul Aug Sap Oct Nov Dec

Figure 10.5: Lake Taupo seasonal variation in actual and simulated uncontrolled levels, based on the record from January 1991 to September 1998.

Figure 6.4: Figures 10.4 and 10.5 from Freestone [H29] Actual and Simulated Lake Levels 1992-1998

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6.3 Lake Taupo Shore

Hicks [#H32, Section 2] describes the geomorphic characteristics and processes of the Lake Taupo shore. He analysed the wave runup for both the actual record and the simulated natural lake level for the 20 year period 1979 - 1998. He used the wind records from Taupo Airport to estimate storm wave heights at 3-hourly intervals.

The risk of erosion is greater when higher waves occur on higher lake levels. Hicks's [#H32, paras 2.16-2.24] findings, "that over recent decades, lake level control has not increased the risk of shore erosion or back shore flooding above what would have occurred without lake control are considered sound. For the first twenty years after the control gates were commissioned it is considered that there was a greater risk of ( erosion as the lake was higher than it naturally would be for significant periods.

Hicks notes in para 2.3 that "The stability of the present lakeshore, in terms of whether it is advancing, eroding or stable over time scales of decades, reflects the interplay of the shoreline composition, sediment supplies, wave exposure and wave distribution of sediment along shore, and tectonics."

6.4 The Tongariro Delta

Hicks [#H32, Section 3] identifies that "flooding and sedimentation problems on the Tongariro delta are to some degree inter-related and reflect a number of factors, some of which are historical. These include: • Gravel extraction on the upper delta during Tongariro Power Development ( (TPD) construction • Slugs of sediment due to volcanic eruptions and large floods • The effect of the TPD diversions on the Tongariro River flow regime • Local changes in lake level due to subsidence and lake level control."

6.5 Lower Reaches of Rivers Entering Lake Taupo Rivers that have an alluvial floodplain will tend to gradually flatten out as they approach the lake. During flood events the river will spill out on both banks and spread the sand and silt out over the floodplain whilst the main channel flow

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continues to the lake. Under low lake levels the velocity will be above average and the sediment carrying capacity greater and more of the water and sediment will reach the lake than under average lake level conditions. Conversely if the lake level is higher than usual the river water levels are also higher, the velocities will be less for the same flow, and more sediment will be deposited in the bed and on the floodplain than under average conditions. If the lake was retained at a higher or lower than normal level for extended periods the rivers and streams flowing into the lake would gradually adjust to the new regime. This could impact on farmland and buildings in the lower reaches of these rivers and streams.

7. Other Factors

7.1 Tectonic ( Hancox [#H31] describes volcanic activity, active faulting and earthquakes. Ground settlement or subsidence and ground uplift has been reported after earthquakes in the last 100 years.

"Tectonic deformation is a type of natural ground movement that occurs over time due to tectonic stresses within the earth's crust. Such movements can occur both as long term phenomenon, over hundreds and thousands of years, or as a short term effect over days to decades. Movements can be local (for example on faults) andlor regional in extent over a wide area. Both types occur in the Lake Taupo area." [Hancox, #H31, para 7.2]

Tectonic ground deformation in the Lake Taupo area is both vertical (ie. subsidence or uplift) and horizontal, and it occurs at rates up to -10mm per year. [Hancox, #H31, para 7.3]

The long term deformation rate is 6-9mm per year over the last 1800 years, this representing the overall difference between the uplifted and subsiding areas. [Hancox, #H31, para 8.2]

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Over the last 1800 years, maximum uplift of "'7-9 m (4-5 mmJyear) has occurred across the centre and northeastern end of Lake Taupo. Hancox Figure 5 is shown as Figure 7.1.

. " mi' E LONG· TERM TECTONIC DEFORMAtioN ,~ (?at!1s o/height changes of Post Taupo Eruption ,1/, " ~~~!:';:,,~~~~!..t.!~~~,!!;~~J'!!~!!:::!_.,~._._"_ JV'TAU:~;lJLT ., -0.3 Uplift Area -

Up -1-5, m, m/year II Kinloch {1.B-3.6 m in 1800 years] ,

38'45' S

/ .·Waitahanui '/'1 ( N II / / Hatepe 0/""'/" *Location of Figu~ Sa ~~'r------~~-' t . ____ ..-:--. • T~rrac'~ measurement , ---- .- -2 point, wilh rale of helghl :3-. ----- chang~ (mml year) //_____ ~ -- Upliftcon(our(+) /'~ / Subsidence - Subsidence contour (-) Down ~/ area ,,/ Down 1,2 mmlyesr o 10km Tokaanu. ._----;;-2 n. B-3;!! m In 1BDOraarsi I I Turangi.1!2.3

Figure 5: Map showing the me~n rates of vertical ground deformation (height changes) around Lake Taupo since the 181 AD Taupo Eruption. This is based on surveys of the terrace formed after the eruption when lake level was about34 m higher than the present day level (see Figure 5a). The survey origin is a point just north of the Taupo gates, near the site of a tephra (pumice/ash) dam formed after the ( Taupo eruption (see Agure 6). The dam breached .,.30 years after the eruption releasing a large (-20 km3) flood down the Waikato River.

Figure 7.1: Hancox [#H31 Figure 5] Freestone [H29, para 10.9] comments that "it does not appear that the tectonic warping that is affecting the Taupo shoreline has had any discernible effect on the long term lake level record." Freestone refers to his Figure 10.1 and comments "this suggests that there has been no differential movement between the level recorder and the fundamental benchmark." The fundamental benchmark is at the actual lake outlet about 1 km upstream from the control gates.

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The southern shore has however moved downwards relative to the lake level outlet. From 1979 to 2002 this relative movement was -40mm (Fig 7.2). Based on the long­ term rates (Fig 7.1) of -1.5mm, over the 64 years since the control gates were com­ missioned the relative levels could be about 100mm lower at the southern end of the lake.

Hancox [#H31] provides a good graphic illustrating the relative effects of tectonic subsidence. His Figure 13 his reproduced as Figure 7.3.

/ \

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0 . '.' , '. ,...... "...... ,.. ' ,...... " U 1'76 E ,$flQR.T-TERM'~T:EeTeNlCDe:FeRlVIATJON ~. / . .' r6t~/Mig~t cnang13sAprJl1979 to June/2002(mni) ~TAUP(),FAULT ;__ ' __ "_'_"'_.".~"'~~_. _~_. ____. __ ,_.;: ... "'~ / SE!.T I:IEIGHT CHA/'{GE CONTOURS [4JOlo Down +40 -'- . Uplift -20 - Subsidence

RN+25 N /jff45) / / I ~~ / rJ,/>< / ( / ./ Hatepe ,./ t ./ IiJP+2 ...... --~~-~F2~2~~ ______~ ____-, ---...-...--~ ~_ m1 Lake levelling sta.\lbn instal.led 197.9-82 I Installed after 1982 l I i MA <54 . Height Oha. ngeS(mm11979<2002 relative 'to Ralnllciw Point j (.40J/(+22)He{ght changes. (mm)relatiIJe ! " . to!heTaupo Fundamental ! o 10km WA{-30j Height changes (mm) July I I 1986.10 June 2002 . 'I Turangia I ".~~-~' ".. ~,.;.:T:~"""-"" "'" ..... ~~.- .. __ .,_.~ " .. ~ .... _,,-;- .. ~_J

Figure 9b: Map showing the total hf;1lght changes (mm) attributed to vertical tectonic deformation In and around Lake Taupo, based on./ake levellingsufiteysfrom April 1979 to June 2002. The red contours (+ve values) showup/ift, while the blue contours (-ve values) show subsidence. The black (0) contour shows noohal1ge. Theinap highlights thelarg~ area of uplift across the centreofLake Taupo (ftom Te Hapua Bay to Taupo) and the area .of rapid subsidence if] the northwest around Kinloch (associated wah the Taupo Fault Belt). Anotherareaofsubsidence occursatthe south end of the lake from Waihi-Tokaanuacross the Tongarifo De/ta to Motuoapa. The red and blue figures (in brackets) indicate changes relative to the Taupo fUl1damental benchmark, Which has subsided ,...20 mrn in relation to the survey datum (Rainbow Point), and so reflect the real changes tllat would be seen within Lake Taupo. Figure 7.2: Hancox [#H31, Figure 9b]

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(a) Effect$ of t.ectonic Silbsidcnce ()niuke bed and shoreline

Lake level appears /0 be Lake bed and ground /owerta/lowing lake bed profile following uplift andshareflne.upIifi

(b) Effects.of tect.onic uplift.on lal.~ebed and sh.ore line

Figure 13: This graphic illustrates the relative effects oitectonic subsidence (a) and uplift (b) on the lake bed and shoreline around Lake Taupo. For a given lake level, subsidence results in lake shore inunda/ioli(floOdihg). Although the lake maybe held at a constant level, in relation to poifits on the lakeshore, lake level appears to be higher. The grcundwater table also appears to be higher as it is closer to the ground surface. Uplift results in the reverse effects, and lake level appears to be lower in relation to shore line features. This results in·increased beach areas and shallows, stranding of boat ramps and jemes, and posSibfydryingupof some hot water bores. Figure 7.3: Hancox [#H31, Figure 13]

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7.2 Flood Hydrology of Land Use Changes

A paper looking at the impact of land use changes on flood flows was prepared for Environment Waikato Project Watershed (Hamilton (2002» This paper concluded that mean annual flood volumes from catchments in grazed pasture are 60% greater than catchments in native bush or forest. The 2% annual exceedance probability (AEP) flood is assessed as 17% increase in peak runoff for pasture over bush or forest.

7.3 Hot springs, Thermal groundwater

Bromley [#H34, paras 2.7 to 2.10] identifies four geothermal fields in and around Lake Taupo:

"Tokaanu is a large undeveloped geothermal field at the south end of Lake Taupo. It ( contains several lake edge and lake bed hot springs near W aihi Village...... Spring flow rates vary with lake leveL

"Motuoapa, on the southeast shore of Lake Taupo, is a small field with lake edge springs (up to 50°C) discharging dilute chloride water.

"Horomatangi is a recently discovered geothermal system located beneath Lake Taupo at, Horomatangi Reefs. It contains lake bed hot springs at about 180m depth within the 1800 year old Taupo eruption vent.

"Tauhara, a geothermal field at the northern end of Lake Taupo, is hydraulically ( linked to Wairakei. Hot springs and seeps occur near the lake edge (Tarahepa Bath, Hot Water Beach). Theses are linked to a heated groundwater aquifer beneath much of the Waipahihi and Hilltop suburbs of Taupo. Water from this aquifer is used for domestic heating and bathing .... Seasonal variations in the level of lake Taupo of about 1.2m affect the discharge flow rate of these springs and the water levels in bores that are within about 300m of the lake edge. Other significant Tauhara thermal features include Waipahihi Source Spring (near De Bretts Hotel) and Otumuheke Spring (near Spa Hotel). These discharge hot water into streams that flow about

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1.5km to Lake Taupo and the Waikato River respectively. Neither ofthese springs is affected by lake level or river level changes."

Bromley [H39, para 3.3] comments on what effect a reduction in level of 1.2 metres in the median level of Lake Taupo would be. This "would have a long term effect on lake edge hot springs at Waihi Village aokaanu), Motuoapa, and Taupo (Tauhara). Some of these springs have dried up during prolonged periods of low lake level in the past (for example Taharepa Bath spring, Taupo, in 2001) ...... The response could be delayed by several months, as aquifer pressures adjust slowly to the new lake level." In para 3.4 Bromley states "Other spring vents, at lower elevation, would continue to discharge hot fluids and some shallow lake bed springs would increase in flow rate after exposure by the retreating lake."

No measurable effect would be expected on Horomatangi hot spring vents at the bottom of Lake Taupo, because the relative change in pressure at this depth would be small. [H39]

Severne [#E7, para 34] provides information on the Waihi-Tokaanu field: "In my doctorate I examined the impact of fluctuating lalce levels on puia at Waihi that are close to lake level (Severne 1999). When the lake is kept at higher range the puia through increased porewater pressure discharge well and the hotter springs have a constant flow rate and maintain their high temperatures. When the Lake is kept low the puia, especially the temperature springs, cease flowing and cool or have significantly lower flow rate. The hotter springs are not as badly affected by low levels but do demonstrate reduced flow."

7.4 South Taupo Wetland Eser & Rosen [Ill] published a paper on the effects of artificially controlling levels of Lake Taupo on the Stump Bay wetland. They installed 9 piezometers (shallow bores) within 1 km of the lake shore and recorded groundwater levels over two years (1995- 1997). They found that only the 3 piezometers nearest the lake were directly related to the lake level. The wetland is a discharge andlor through-flow area, and the general direction is towards the lake. Surface and subsurface water levels are closely related to each other. These water levels are influenced mainly by rainfall and

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evapotranspiration (which is seasonal) in areas that are greater than 100m landward from the lake. The artificial regulation of the lake has led to a 2cm rise in annual mean lake levels since 1950. However summer monthly means are up to 20cm higher in summer than pre-controlled summer levels. These are likely to have caused the observed increase in water levels in the Stump Bay wetland. A comparison of aerial photos of 1941 and 1958 does show a significant increase in wetland area over that period. The area of wetland is identified by the vegetation of a wetland. Both Baumea sedgelands and oioi (Leptocarpus similis) rushlands are present in the wetter areas.

The lake level analysis appears to be consistent with the other lake level data available. No allowance for the tectonic land subsidence has been noted in this paper. ( James et al (2000) describe the existing physical and biological environment around the shoreline of Lake Taupo. They state that these wetlands are of international significance as they support a mosaic off predominantly native vegetation and a rich diversity of aquatic bird species. They note that invasion of the South Taupo wetlands by grey willow is seen as the greatest threat to its continued viability in its current state.

8. Survey Data

Mighty River Power was approached to find out if historic or recent land contour or spot height levels of the general ground were available for areas around Lake Taupo. At this stage no firm response has been obtained. ( \,

Walzl [#El, paras 31-81] covers considerable material relating to high lake levels in 1926 (they reached 357.63m around mid-October 1926 and stayed close to that level for 2 months). This level was considered to be too high by local residents.

Walzl [#El, para90] notes that land at Tokaanu was grazed with dairy cows in 1920 to 1922, and again in 1939. From the lake level records there were some months above 356.8m over the 1920-1922 period but the maximum level in 1938/39 summer was about 356.7m.

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Walzl [#E1, para 93] notes that "Between Tokaanu and the foot bridge leading to the Tongariro there is considerable area ranging from 1179 to 1181.5 (358.0 to 358.75m) but this is in Manuka and there is no evidence that this has ever been cultivated. Beyond this is a swamp ranging from 1178.24 (357. 17m) to Tokaanu and to 1179 {358.0m) at Tongariro end."

9. Location of Claims Derived from Evidence of Claimants

9.1 Location of Claims Table 9.1 summarises the matters relating to Lake Taupo levels from information supplied as evidence of claimants. Figure 9.1 shows the general location as identified from the evidence of claimants. The exact locations may vary but the nature of the issues and the influence of controlled lake levels at these locations will be discussed. This grouping of claims by area is considered the best way to handle the relative impacts of the various factors on that area.

David Hamilton & Associates Ltd Page 39 of61 1 August 2005 Lake Taupo Review Waitangi Tribunal Claimant Evidence Relating to Lake Taupo Levels WA11200) Para. Ref. No. Name Issue Locality No. 018 Charles Wall 10-11 Hot water pool destroyed by rising lake levels Taharepa Erosion from high lake levels/storms destroyed 024 Blanche Parry Kapua 5-7 Waipahihi beach and exposed sewage pipes Flooding of Taharepa Spring due to rising lake 026 Emily Rameka 16-18 Taharepa levels Taniwha (Matawhero) killed when Waikato River 1st bend of Waikato 027 Winifred McKenzie 43 diverted to build control gates River Fluctuating lake and river levels causing erosion E5 Maria Nepia 12.2-12.3 and swamping of land - damaging sites of cultural significance Impact of high lake level on sedimentation of lower Issues Statement of Ngati Tongariro River & consequent adverse effects, incl Tongariro River, E5(a) 2.1 Tuwharetoa loss of land due to flooding. Tupuna & wahi tapu Tokaanu Bay Iving in water Interference with natural state of Lake Taupo and Issues Statement of Ngati E5(a) 2.1 with the natural flow of the Waikato River from Lake Taupo Tuwharetoa Lake Taupo to the sea Southern end of Issues Statement of Ngati Erosion of Lake Taupo foreshore - C75 Maori Lake Taupo,Waihi E5(a) 2.3 Tuwharetoa Reserve & Waihi Bay Bay, Taupo foreshore, Water bores drying up from fluctuating lake levels, Issues Statement of Ngati e.g. Paenoa, Waihi E5(a) 2.3 low lake levels affect ability to use natural thermal Tuwharetoa Marae baths Drowning of puna (springs) when lake levels are Birthing stone at Issues Statement of Ngati E5(a) high. When lake level drops puna (springs) Halletts Bay now Tuwharetoa disappear underwater ( Issues Statement of Ngati E5(a) 2.3 Damage to caves on foreshore Whanganui Bay Tuwharetoa Issues Statement of Ngati Loss of ability to use land for cultivated areas, E5(a) 2.4 Waitahanui (arable) Tuwharetoa farming and forestry due to higher water table Issues Statement of Ngati E5(a) Database With high lake pa site at Korohe is waterlogged Korohe Tuwharetoa Issues Statement of Ngati Low lake levels doing harm to mahinga kai. and E5(a) Database Tokaanu Bay Tuwharetoa flora and fauna of lake ecology (e.g koura) Fluctuating lake levels affect puia (temperature Wairakei-Tauhara E7 Charlotte Seveme 34 springs) - altered flow rates and temperature Waihi-Tokaanu changes Rising lake levels flooding geothermal springs. 10 E16(a) Paranapa Rewi Otimi 16 Waihi sites lost to rising lake levels at Waihi. Low flow of Tongariro resulted in river silting up Arthur Lancaster Te Takinga Tongariro River. E26 17-24 and scouring of river banks. Water now Grace Tailrace encroaching on urupa and waahi tapu. Also rising lake levels flooded good crop- Arthur Lancaster Te Takinga E26 27 producing areas, forcing move to areas with peaty Tokaanu area Grace soil. Ability to crop suffered through rising lake levels. E33 James Hemi Biddle 7 Korohe Had to move to higher ground. Cultural impact - waahi tapu submerged; Original E33 James Hemi Biddle 27-31 Korohe Marae place now under water and swamp. Korohe Marae and homes moved. George Te Waaka Eruera E39 81 Reversion of land to swamplands ( Asher George Te Waaka Eruera Rising lake levels eroding foreshore and E39 81 Asher inundating waahi tapu Ringakapo Tirangaro Asher Rising lake levels & highway & piua (Waimata) E41 13-14 Tokaanu Payne under water. Ringakapo Tirangaro Asher Cropping land at Te Taramea abandoned with E41 20-22,37 Tokaanu Payne rising lake levels Ringakapo Tirangaro Asher E41 35 School had to be relocated to Turangi in 1941 Tokaanu Payne Ringakapo Tirangaro Asher E41 38 Cropland now swamp Tokaanu-Waihi Payne Ringakapo Tirangaro Asher Waiotaka straight farms abandoned 1950s with E41 39 Waiotaka-Korohe Payne high lake levels Crown one of the biggest developers yet it is E44 David Chrystall p.32 owners who it appears will have to bear most cost Waihaha of remedial measures 1958 flood inundated family farm. Waimarino R and Waiotaka R overflowed and silt & debris on John Stephen Paurini Karamu E45 5-7 land and blocked open drains. SH 1 blocked. Korohe Asher Water couldn't get away due to raised lake level. This was the end of the dairy farm. Table 9.1: Schedule of Claimant Evidence Relating to Lake Taupo Levels David Hamilton & Associates Ltd Page 40 of 61 1 August 2005 Lake Taupo Review

(.

( )

A Wa.ter level sites e Claim sites

Location ofClaims and David Hamilton & Associates Ltd July 2005 Water Level Recorder sites Base orthophbtosby L INZ Lake Taupo

Figure 9.1: Location of Claim Sites with Reference Numbers

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9.2 South end of Lake Taupo (Waihi, Tokaanu, Korohe, Stump Say) This area has subsided relative to the outlet control structure and Taupo fundamental benchmark that is used as the reference for the Lake Taupo Compensation Claims Act. This subsidence is tectonic and not related to the control gate structure. The magnitude of this subsidence over 64 years at a long-term rate of 1.5mm per year is about O.lm, and must be added to the impact of control gate operational impacts to give a total change in relative levels to the pre-control gate situation.

The average lake level since the control gate structure was commissioned in 1941 has been 356.737 or 0.047m higher than the 1905-1941 (pre-control gate) mean lake level of 356.69m. :( The maximum lake level since the control gate was installed has been 357.634m which is similar to the level reached by the lake in 1926 and lower than the maximum for the entire record of 357.723m in 1909.

The lake level has averaged about O.lm higher over the December to April period since the control gates were installed. The level that is exceeded 10% of the time for the post control gate period averages 357.21m compared with 357.12m pre-control gates. This is an 0.09m increase. When combined with the tectonic subsidence the effect is now about 0.2m and this could impair gravity drainage outfall sufficient to reduce land use options. This is a combined effect.

The minimum lake level has been lower than was recorded pre-control gates. This now generally occurs in May rather than April for the pre-control gate monthly pattern. The minimum level since 1941 has been 355.772m, that is 0.183m lower than the minimum of 355.955m between 1905 and 1941.

High lake levels from 1941 to 1946 after the control gates came into operation were sustained (see Figure 9.2) and would have had an adverse impact on land use through high water table, on roads, access tracks and buildings, and an impact on hot springs along the shore. The levels were not as high as had naturally occurred previously in

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1909 and 1926 but were for periods of over a year rather than a few months. No new areas should have been flooded by surface water directly from the lake due to the operation of the gates.

Lake Taupo Lake Level 1941-1947 Drawn on 27-Jul-200516: 357.6

357.4

357.2

357.0

356.8

r- 356.6 III ffi [ 356.4 3 356.2

356.0

355.8 1942 1944 1946 82795 from 01-8ep-1941 00:00:00 to 01-8ep-1947 00:00:00

Figure 9.2: Lake Taupo levels 1941 to 1947 showing sustained high levels

For reasonable land drainage the water table under normal conditions should be the order of 1m or more below the ground surface. Under flood conditions this water table level could be above ground for a short time but prolonged periods with the watertable less than 0.2 to 0.3m below ground level is likely to lead to loss of pasture or crop. The actual ground levels in the vicinity of Tokaanu in 1939 quoted in Walzl [#E1] were 1178.24 ft (357.77m) and higher. Land drainage in these areas would also be relying on open drains to be adequately maintained. Open drains gradually silt up, ) or the banks fritter away, and weed growth occurs. These factors all reduce the effectiveness of the drains if regular maintenance is not carried out. Any land that was developed below 1179 ft (358.0m) was very marginal and even land at 1180 ft (358.3 m) was likely to be marginal under natural conditions, with some years (such as 1926 when the lake was about 357.6m for over two months) resulting in loss of crops.

Walzl [#E1, para 137] quotes Public Works official J Wood "It is agreed that land above the 1180 level will be unaffected by lake control, though the margin between

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1177 and 1180 will be, to some extent affected, especially where insufficient drainage is provided." In Walzl [#E1, para 146] the Registrar noted that the whole of the Tokaanu Scheme and swampland on Korohe would be below the level of 1180 feet.

In relation to the Tongariro Delta the information presented by Hicks [#H32, section 3] is considered to be a sound description of the factors. He states in 3.17 "In summary, the Tongariro delta, by its very nature, should experience flooding and sedimentation. However, there are several factors that help explain the apparently accelerated sedimentation there in recent decades, with consequent effects on flooding. These include the past phase of gravel extraction on the upper delta (which served to delay and temporarily hide the problem), slugs of sediment coming from volcanic eruptions and extreme floods, diminished sediment transport capacity across the lower delta due to the effects of the TPD on the flow regime, and tectonic ( subsidence. Lake level regime associated with hydro control may have played a minor role, but the effects on this would be limited to a few centimetres of net deposition. "

The large floods in 1958 that caused damage with silt and debris to farmlands at the south end of the lake and filled in drains occurred in February 1958 when the lake level was below average at 356.3m and did not exceed 357.0m (see Figure 9.3 for lake levels and Fig. 9.4 for lake inflows over 1958-1959). The lake did reach 357.4m in January 1959 after several months below average. If the lake had been high before the major flood then this would have been a contributing factor, but this was not the case. The control gates operation in February 1958 did not adversely affect land ( surrounding the lake. The sustained high lake levels in July 1956-February 1957 when the lake was above the MeL of 357.387m may have resulted in some siltation of the lower reaches of the Waimarino and Waiotaka Rivers that may have marginally increased the area affected by flooding in 1958.

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Lake Taupo Lake Level 1958-1959 Drawn on 28-Jul-2005 16: 357.6

357.4

357.2

357.0

356.8

356.6 :; @ r 356.4 ~ 3' 356.2

356.0

355.8 Jan-1958 Jul-1958 Jan-1959 Jul-1959 -- 82795 from 01-Jan-1958 00:00:00 to 31-Dec-1959 00:00:00

Figure 9.3: Lake Taupo levels 1958·1959

1400 Lake "Ii upo Daily Mean Inflows Drawn on 28-Jul-2005 17:

1200

1000

800

" 600 ~ 3 ~ 400

200

o Jan-1958 Jul-1958 Jan-1959 Jul-1959 -- 2790 from 01-Jan-1958 00:00:00 to 31-Dec-1959 00:00:00 Figure 9.4: Lake Taupo inflows 1958 .. 1959

9.3 Waihi foreshore Walzl [#E1, para 173-179] covers requests for foreshore protection work in 1986. The following graph taken from Freestone [#H29] shows that the controlled level was higher (yet within the MeL) for an extended period in 1985 and 1986 compared with what the natural lake level would have been.. High winds from the north to east direction at this time could well have resulted in erosion over this pedod. There are other periods in the record where the erosion will have been less than it would have

David Hamilton & Associates Ltd Page 45 of 61 1 August 2005 Lake Taupo Review been naturally as the lake has not reached the pre-control gate highest levels since 1941. 358.,.. ------'---+------"'-\--'---'-----1-

.35.5 ""'="""'"'"''=""-----t=-:-=------i==;-----__+. 01;JAN;aS ~AN'6B~N-91 ~ - Lake Taupocontrolle(:i'level(m) ...... lake Taupo uncontrolled leve(.(fu). (simUlated aftElr 1941)

Figure 9.5: Actual versus simulated Lake Taupo levels 1985-1992 [#H29]

9.4 Taupo township foreshore and Tauhara springs The average lake level since the control gate structure was commissioned has been 356.737 or 0.047m higher than the 1905-1941 (pre control gate) mean lake level of ( 356.69m.

The maximum lake level since the control gate was installed has been 357.634m which is similar to the level reached by the lake in 1926 and lower than the maximum for the entire record of 357.723m in 1909.

The lake level has averaged about O.lm higher over the December to April period since the control gates were installed. The level that is exceeded 10% of the time for the post control gate period averages 357.21m compared with 357.12m pre-control gates. This is an 0.09m increase. When combined with the tectonic subsidence the effect is now about 0.2m and this could impair gravity drainage outfall sufficient to { reduce land use options. This is a combined effect.

The minimum lake level has been lower than was recorded pre-control gates. This now generally occurs in May rather than April for the pre-control gate monthly pattern. The minimum level since 1941 has been 355.772m that is 0.183m lower than the minimum of 355.955m between 1905 and 1941.

Lakeshore erosion will be most pronounced with a combination of strong winds and high lake levels. Hicks [#H32, Section 2] fairly describes the processes and relative

David Hamilton & Associates Ltd Page 46 of 61 1 August 2005 Lake Taupo Review impacts for the period 1979 to 1998 that he studied. Over this period the overall impact of the lake control has been similar but slightly less than it would have been under a natural situation. An appraisal of the plot of actual (controlled) versus uncontrolled lake levels does indicate that the period from 1941 to 1958 included some years with high lake levels where erosion of the shoreline may well have been greater due to lake control.

The geothermal resource use in the Taupo township area is likely to have affected springs along the shore. Studies may already have been carried out relating to this. The relative impact of lake levels compared with this resource use on the Tauhara springs is not clear.

10. Consent Monitoring Conditions The Mighty River Power consents require certain monitoring to be undertaken. They require a monitoring programme to be prepared and submitted to Environment Waikato. They also require annual data analysis to compare how the consents have been operated against the consent conditions. A Panel comprising at least three members is to be appointed to assess the effectiveness of the monitoring programme and results. The 3-page section of the decision relating to monitoring is attached as appendix. [H28].

In essence the type of monitoring required in relation to Lake Taupo includes: (i) recording of water levels within Lake Taupo at Acacia Bay (ii) Recording the outflow from the Taupo gates as the rolling 30 minute average of total gate flows (iii) Representative profiling of beaches and river mouths around lake Taupo on an annual basis

The monitoring programme is to assess the effects of the on-going operation of the Waikato hydro system, and in partiCUlar to compare those effects with those anticipated and authorised by the grant of the consents, is to be designed by the consent holder. Matters to be included: • River, lake and bank erosion • The ecosystem of Lake Taupo

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• Specification and protection of areas of significance to Maori

Results to be forwarded to Environment Waikato at agreed times, but at least annually, and shall include: • A review of all data collected under the monitoring programme • A summary ofthe monitoring results and a critical analysis of that information • A comparison of the data with previously collected data • Recommendations on alterations to the monitoring programme • Any other issue considered important by the consent holder

The Genesis consents are also likely to have monitoring in relation to the Tongariro River.

The detail of the approved monitoring programme has not been sighted. The nature ( of the monitoring proposed appears to be satisfactory. However for me to draw definite conclusions the detail of the sites and frequency of monitoring would need to be known. It is assumed that Environment Waikato would make the monitoring information available to interested members of the public.

11. Additional Information, Research or Analysis With the current consents, and the way they are now operated, the monitoring provisions that are currently in place are likely to be adequate.

In terms of quantifying impacts relating to the first 30 years of operation prior to the TPD commissioning, when the lake was held high for extended periods, further ( survey, or analysis of existing information, is needed on: a. Ground levels that are below 1180 feet (358.3m) and may have been affected directly by flooding from the lake, or by flooding in the lower reaches of the rivers and streams entering the lake. b. the likely impact on groundwater levels of the extended high lake levels within say 2 km of the lake shore at the southern end of the lake.

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c. the likely extent that sedimentation in the lower reaches of rivers and streams occurred, that would lead to flooding from those watercourses even when the lake level was at more normal levels. d. the impact on the hot springs at Waihi of high and low lake levels. e. The impact of geothermal water use in the Taupo township area on the Tauhara springs.

END

Glossary Bibliography Appendix: Might River Power Consent Monitoring provisions

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Glossary

The following definitions have been compiled from a number of sources, primarily: "Freshwaters of New Zealand" Published by New Zealand Hydrological Society Inc. and New Zealand Limnological Society Inc. 2004

Annual Exceedance Probability (AEP) the probability of exceedance of a given flood flow in any year

Annual Maximum (Minimum) Series extreme-value series with largest (smallest) annual values

Annual runoff (annual flow) total volume of water that flows during a year from a ( drainage basin

Average recurrence interval (ARI) synonymous to return period; defined as the reciprocal of the annual exceedance probability (AEP) for floods

Catchment the drainage basin or watershed

Cross section section of a watercourse at right angles to the main (average) direction of flow

Cumec a measure of discharge. Abbreviated from cubic metres per second. Also ( written as m3/s

Design flood flood hydro graph or instantaneous peak: discharge adopted for the design of a hydraulic structure or river control work

Discharge volume of water transported per unit time. Frequently calculated from a

2 cross sectional area of a channel (square metres, m ) multiplied by a current velocity (metres per second, mls) to give discharge m3/s.

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Duration Curve graph representing the time during which the value of a given parameter, e.g. water level, is equalled or exceeded, regardless of the continuity of time

Evapotranspiration the combined loss of water by evaporation from a free water surface, and the water evaporating from the leaves of plants (transpiration)

Fetch area in which ocean, lake and reservoir waves are generated by the wind. The length of fetch area is measured in the direction of the wind

Flood rise in water level to exceed channel capacity, followed by recession. The water pulse is illustrated on a hydrograph as the rising limb, peak, and falling limb over time

Flood frequency number of times a flood above a given discharge or stage is likely to occur over a given number of years

Floodplain temporarily inundated lateral river flats, usually of lowland rivers

Flood routing technique used to compute the movement and shape of a flood wave moving through a river reach or a lake or reservoir

Flow-duration curve curve showing the percentage of time during which the flow of a stream is equal to or greater than given amounts, regardless of chronological order

Frequency analysis procedure for interpreting a past record of hydrological events, in terms of future probabilities of occurrence

Hydrograph plot of discharge or water level (stage) against time. Depending on the time scale, this shows the shape of a flood pulse in response to storms (days) or shows the flow or level regime of a river or lake over decades.

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Hydrological cycle the circulation of water between ocean, atmosphere, and land via evaporation, precipitation, and flow through and over the land.

Hydrology the study of the mechanics of surface and subsurface water and flow. Sometimes used loosely to describe the water regime.

Hydrometric station station at which data on water in rivers, lakes and reservoirs are obtained.

Infiltration capacity maximum rate at which water can be absorbed by a given soil per unit area under given conditions

Interbasin transfer artificial movement of water via channels or pipes from one ( catchment to another

Interception process by which precipitation is caught and held by vegetation, then may be lost by evaporation without reaching the ground.

Interflow that portion of the precipitation which has not passed down to the water table, but is discharged from the area as subsurface flow into watercourses.

Isohyet line joining the points where the amount of precipitation in a given period is the same.

Littoral zone edge or shore region where the water is shallow enough for continuous ( , mixing

Live storage volume of a lake or reservoir between the maximum and minimum operating levels

Mean average of a series of values

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Mean annual flood arithmetic mean of all the individual annual flood peaks in a period of record

Mean monthly discharge arithmetic mean of all the individual monthly mean discharges for a named month in a period of record

Mean monthly level arithmetic mean of all the individual monthly mean levels for a named month in a period of record

Median the mid point of a series of values where half lie above and half lie below the median value

Peak flow maximum instantaneous flow or discharge of a given hydro graph

Rating curve relation between stage (level) and discharge (flow) at a measuring point

Sediment material usually inorganic transported by water. In watercourses, sediment is the alluvial material carried in suspension or as a bed load

Stage river or lake height, usually as measured at a water level recording site

Stage-discharge relation relation between stage (level) and discharge at a river cross section, expressed as a curve, table, or equation

Storage impounding of water in surface or underground reservoirs for future use; the volume of water stored.

Thermal spring groundwater-fed stream with water temperature above the mean annual air temperature

Throughfall part of rainfall that reaches the ground directly through the vegetative canopy, through interplant spaces in the canopy, and as drip from the vegetation

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Travel time time elapsed for the passage of a water parcel, e.g. a flood wave, between a given point and another point downstream.

Water balance inventory of water based on the principle that during a certain time interval the total water gain to a given catchment area of water body must equal the total water loss plus the net change in storage.

Watershed the boundary of a catchment

Water table the interface between groundwater and the soil substrate or air

Wetland permanently or intermittently wet areas, shallow water or lamd/water ( margins that support a natural ecosystem of plants and animals that are adapted to living in wet conditions

Yield quantity of water that can be collected for a given use from surface or groundwater sources in a basin in a given time interval. Also, the quantity of water derived from a unit area of a drainage basin in a given time interval.

(

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Bibliography

1. Evidence Presented to the Waitangi Tribunal l}Dr Kirkpatricket ai, 'Land based Cult'ural.Resources& Walerways & Environmental Impa'dts (RotoruEI, Taupo & Kaingaroa) 1840 """' 2000', Wai 1200, Ea.

ii) Tony Walzl, 'Hydro Electricity. Issues: The Waikato River Hydro Scheme', Wai 12"00, 1:1; supporting papers, Wai 120tJE1(a); sumrnary,Wai1200 E1(b)

Jii)TonyWalz!, 'Hydro Electricity Is~ues: The Tongatito DeveloptrtentSchefne', Wai 1200, E2.

iv) Crown, "Lake Taupo Compensation Clams Act 1947" E52 and "Lake Levels" E52(ct)

v) Tangata whenug briefs of evidence: - David Crystal E44,and H15 .,. Rangikapo Payne E41 - H~tni (Jim) 8i~dle Eaa - Stephen Asher e45and E45(a) - George Asher E39and H14 - CharlotteSev.erne E7 - Ngapl;l Otiniigeothermal brief E16(a) - Emily Rameka D26 - Chula Wall D18 - Blanche Kapua D24 - M Nepia E5, E5(a} andE5(b) - Arthur Grace E26 . - Winifred McKenzie 027 vi) Crown documents referred to in crosswexamination of Dr Kirkpatrick:

) - Te Ohaaki Marae Working Party Report, September 2004, together with a one-page report.of Huion 12 February 2005; VVai 1200, H2; - Agreement and Memorandum of Lease between Ngati TahLl Tribal Trust and Contact Energy Limited dated 15 March 1999; Wai 1200, H2(a); - NIWA Report prepared for Environment Waikato entitled "The Higher Lower Tongariro"; author GraemeSmart; Wai 1200, H2(1l) - Letter dated 27 May 1998from the Ngati Tahu Tribal Trust to the Minister of

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Finance: Wai t200.H2(C}; and - Le1terda~~g 1JUne4(ilfJ!j#omEt1vitolirn~n.tW~i.k~~~),toA~$istantC.rown qq\Jnsef~ridithe '~uhd[e0f QQcuments.encloslng"a.hundle ofdo'clJli1ents H2(d) . - Me:tnotoR,PrQffit~ S·IFPwldsTeTqngarifoRiver- Crown Law & Waitangi Trii;)unal, 31 Ma.y.oS H2(~) - ,'Memo to Taupo Uaison. SubcorriliiitteeBealJfill re PrqjectWatarshed

Community MeetihgS 1 15 Nov 01 H2'(f) - "Protecting Lake Taupo "Our decisiOn Making Process". Mar 04 H2(g) - Reporito policy & Strategy-committee, ~9Apr05 H2(h) - "WaikafoRegi6nal Polic;Y Statement - Proposed Change No.1 : Geothermal Section, 12 Jun 04H2(1) - j'ProposedWaikato Regional Plan: Proposed Varia~ion No.2: Geothermal Module", 12 JunQ4 H2Q) - Appendix 1: Parties notified of proposed changes togeothl?rmal policy H2(k)

vii) Environment Waikato: ( - B Peploe, Evidence (EnvironmentWaikato) ra: allegations made on flood & rivermanagementbyEW, 6 Jul 05 andappendicesfl25 and H2S(a) - M Bro.ckefsby, Evidence (EnVironmetit Waikato) teallegations & iSSUeS raised onperforman98ofEW,pJuJ,05 ahd appendiq(3sH26 ,md H26(a) - R Pefch, Evidenoe (Environment Waikato) reallegations on nitrate emissionsinto Lake Taupo, 6 JU/ 05~nd appendices H27 and H27(a) - Environment Waikato, "Mighty River PoWerTaupo.;Waikato Consents Decision Report""H28

viii) Mighty River Power:

- H Freestone, Evidence (Hydrologist) re TaupoJWaikato hydro system H29 - M Webby, Evidence (Hydrologist) re Taupo/Waikato hydro system, H30 - G Hancox, Evidence' (Hydrblqgist) re TalJPolV\(aikato, hydro system, H31 - D Hicks, Evidence (HydrQlogist) re WaikatolTaupohydrosystem. H32 - J McConchie, ~vidence (Hydrol?gist) re\IYaikato/Taupo hydro system, H33 ( C Bromley, EVidence (Hydrologist) re Walkato/Taupo hydro system, H34

vix) Scientific Paper as Evidence

Eser P, Rosen MR (2000) Effects of artificially controlling levels of Lake Taupo, North Island, New Zealand on the Stump Bay wetland. New Zealand Journal of Marine and Freshwater Research, 2000. Vo1.34: 217-230. 111

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2. References Acheson A R, (1968) River Control and Drainage in New Zealand, Ministry of Works

Cheal Hindess Battersby & Norrie Limited (1995): Lake Taupo Flood Hazard Study­ A report reviewing aspects of past compensation claims and potential problems.

Deed of Agreement. Tongariro Power Development Offset Agreement - Crown, WVA, Counties & Drainage Boards. 24 March 1977.

Devgun,M.S.,Waugh,lR.,Freestone,H.l(1999) Waikato catchment hydrological overview. Opus International Consultants Ltd

Furey, L.(1998) Impact of hydro-electric operations on archaeological sites adjacent to the Waikato River and Lake Taupo. Report to Electricity Corporation of New Zealand.

, Genesis Power Limited. Tongariro Power Development - Resource Consent Applications and Assessment of Environmental Effects. July 2000. (~650pp)

Hamilton, D l, Waikato Project Watershed Contributor - Hydrology Background Technical Paper. May 2001

Hicks,M.,McKerchar,A.,O 'Brien,R.(2000) Lakeshore geomorphic processes, Lake Taupo. NIWA.

James,M.,Boubee,J.,Davies,M.,Champion,P.,Hawes,I.,O 'Brien,R.,Rae,R.,Rowe,D.,Sa gar,P.,Schwarz,A.,Shankar,U.(2000) Taupo levels ecological study: assessment of effects. NIWA

James,M.,Champion,P.,Hawes,I.,Macky,G.,Rowe,D.,Sagar,P.,Schwarz,A.,Sutherland, D.,Weatherhead,M.(2000) Taupo levels ecological study: descriptive report. NIWA.

Kirk R M, Single M B (2000) Shoreline Management Lake Taupo. Report to Mighty River Power. Land and Water Studies [International] Ltd

Frampton, M and Lew, D D, Hydrological Effects of Tongariro Power Development on the Waikato River Catchment. Wellington, Opus International Consultants Ltd. DRAFT. (1998)

McConchie lA, Waikato River Geomorphic Processes. Earth Sciences,Victoria University of Wellington for Mighty River Power. (2001).

Mighty River Power, Taupo Waikato Resource Consents Project AEE Discussion Draft. MRP (November 2000)

Mighty River Power, Taupo Waikato Resource Consents Assessment of Environmental Effects. MRP (March 2001)

N.Z. Hydrological Society, 1992. Waters of New Zealand. Ed. M Paul Mosley.

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N.Z. Hydrological Society, 1997. Floods and Droughts: the New Zealand Experience. Ed. M Paul Mosley and Charles P Pearson.

Selby, M 1 1972. The relationships between land use and erosion in the Central North Island, New Zealand. Journal of Hydrology (N.Z.) 11: 73-85.

Waugh,lR.,Lew,D.D.,Frampton,M.(1999) Waikato catchment floods and flooding history. Opus International Consultants Ltd.

Webby,M.G.,Su-Wuen,O.,Currie,B.H., Roberts,C.l, Effects on water levels and flows in the Waikato River of proposed future operation of the Waikato hydro system. Opus International Consultants Ltd. (2002)

Webby,M.G.,Walsh,lM.,Mackay,C.A.(1999). Lake Taupo and Waikato River levels and flows. Opus International Consultants Ltd.

(

(

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Appendix Extract from EW Mighty River Power Decision on Consents [H28] C..MQ,nito:ring 'and RepQrtin'g

Peer Review

6.1 Th~ consent. holder~hanengage,~t its, own., cost, a Panalof at least three indlvldu.als Who betwe,en them can. d,ernonstrateprOVen expertise In all matters covered by tbemonitorlng required by, the conditions of this consent.

6.2 The consent holder shall norrlil18teindivlduals to the Waikato Regional Council for approval <1smembers of the Panel.

'6.3 Extra membersrnaybe,added to the Panel from time ,to time, following approval from the WElik~toRe9ional CounciL Merribers qflhePanE)Fmay b.e removecJ from the Panel only following writtenapPTovalfrom the Waikato. Regional Council.

6,4 All Gosts Incurred by the Panel shall be met by the consent holder.

'6:5 Terms of ReferehcetbgUi(j~a,?ddjr:ect tne P,,!nel shall be established by the oonsenfholder in consultation With thl3WaikatbRegional Council.

6.6 The duties of the Panel· shall Include at least the folloWing:

• To revi~w. prior to Its iniplementation, themonlforlng plan prepared by the consent holder as {equired bytha conditions ofthls· consent

• To review the resullsofthe monitoring uliderf;:iken by the consent holder, arid to report itsfir'\dings on those resUlts to the Wajkato Regional Council, along with its recommendations as to possible changes to the monitoring programme or actions' which might be taken as a result of the>findings of thOse programme.

• To provide its expert opinion as to the relative role that operation of the Waikato hydro system plays in any positiveand/oradverse ecological effects. that are identified by the monitoring programmes Which the Panel is required to review. .

• To provideauthorit~tivE! opinion relative to the effects that operation of the Waikato Hydro System is having on customary Maori interests, both ecological and cultural, In the Waikato catchment.

• To reporl at leastannlially to the Walkato RegIonal CounCil and to the consent holder on all onhe activitY undertaken by the Panel in relation to Its role Ihrespe:ct 6fthis consent.

• Any other function or task agreed between the Waikato Regional Council and the consent holder.

The consent holder may request the Panel to undertake any other task It chooses, including acting in a similar review role for the "Waikato Catchment Ecological Enhancement Trust".

6.7 The consent holder shall provide the Panel with reasonable access to records, plans, sites etc, as required to undertake its functions.

David Hamilton & Associates Ltd Page 59 of 61 1 August 2005 Lake Taupo Review

6:800e or more ;indivldu~1 rnerrib$r:$of thf,i .P(lhelmay b¢[equ~$teq to,u!'lc!~rta~e ~peoi~Ust t$.Sk$withih the' overall ,fl:mclidn 'of the: Panel, ,but thecorriplete P~nel ttl!.l,stbe:year. prQ~ieleg" With the, PPPQrt,\.Ini1;yt()lJIe,et" C)sa ,groUp; ~tl$!3stonee leach

.M<)liitorin~ Pr'o'gl'am:m:~ 6:9 The consenJ holder shall design a monitoring programme, for the purpose of a,ssessingthe. eff~cts Qft~e onwgoing op,eratiqn QHhe YVaik~to IlYd,ro sys~em,and in particular to compare those effects With those an~iclp'atedand authorised by thegraritof thee;¢ ~()nsents'With respect to thef61lowifig rhatters: '

• river, lake and reservoir bank erosion,

-the eCOe;ystemsof L.a~e Taupo aodthe, Waikato River (including the hydro :reservdlrs, the riverine sections between Taupbal1'd Karapiro" and .the river downstream of Karapiro). '

- riverbed level changes below Karapiro, at least as far doWnstream as Ngaruawahia, (1 specification arid protection of areas, of significan~ to Maori;

'6.1 b With it) six months, of thecotnmenc~m.ent ofthis consent; the Qonl?€lnt ho!dElr!?hali forward·to. ttie Waikato Regiolii,lI Council a peer revieWed monitoring plan Which shall d€).EiGrib€) thE! propo~ed monitoring prqgramme develope¢Jto meet the rs'quiremeritsbfconditidn6.9 above. TM programme shl:lll include a$s.cciat€ld quality control· .and quality ·assurance procedures, arid reporting procedures. Qnce the monitoring prqgramm€) has beel1appmved py fhi:} W(likatoRegionaJ CounCil, the cOhsent hblder shall impJemeritthe apprbvedprogtamlj1e,butll'1ay implement ch6!nges to the programme subject to approval of those changes by the Waikato Regibnai Ctlu!icil.

6.11 The monitoring proQramme will include a~ a minimum:

i. Recording of water levels within Lake Taupo ano the Waikato hydro reservoirs in accorowith conditions. 2;2 and 3.2 ofthis consent.

Ii. Recordi09 the outflow from the Taupo gates as the rolling 30 minute average ohotal gate. outflows.

iii. Representative profiling of beaches ,and river mouths around Lake Taupo ( 6n an annual basis.

iv. A 5-:yearly geomorphologic survey to determine the amount and to investigate' causes of aCtive river and reservoir .edgeerosion in the fbllowingareas:

.. The Waikato River between the Taupo gates and the Ohakuri reservoir

• The shorelines of each of the Waikato hydro reservoirs.

• The Waikato River between Karapiro dam and Ngaruawahia

David Hamilton & Associates Ltd Page 60 of 61 1 August 2005 Lake Taupo Review

v. A5-yearly'.surVey cif ecdsystehiihdicatorsinthe Waikato hydro reservoirs .ahd Jivedn$s$c~lon$. betw.ee.n the TaUpoSaJ!3s: and Ohak~ritQ.petetmine any cnanges:irftbenaWteand.behavldUr:of theecosysterm arising from the operation.oflheWaikato.hydro.sY$iem, indruQing; .

• RiYer!he sections (Taupqgaies '100hal

,. HyC\ro reservol17s - cOJ'flPositlcm. habit"ltzonationanq epdentin relationtd water levelfluctlJatibns of wefl1:md, VariaJ.and submerged macrophyte.spebies.

• Tailraces - populations and distriblltion of Caddis in ·the tailraces· of the Aratiatia and Arapuni power statiOns.

vi. A 5~yearJy sUrvey of riverbed IEWels below Karapiroasfar as Ngaruawahia.

vii. River bed cross sections in the vicirlitydf the; Hamilton Traffic Bridge, Of the Fakfield8ri~gej an~1 oUhe subfluvial water supply maih to Hamilton East from the Hamilton Water Treatment Station. Thesearet6. be_ located and ) measured in a manner sufficient to demonstrate anY changes in bed I(;wel which maythreatenthe.structural. irifegriiy oflhese facilities.'

viiL Routlnesurveillance for the existence of blue-green algal spedies in the hydro reserVoirs. This shall compfise.as a.mihitiium,morithly monitoring of the tail.race. water from Qbakurl, Maraetai 8, and Karapiro, between the mOrithsof November·April.inClusive.. Results front. this h1otlitoring shall be provided to Waikato Regional COllncil as soon as 'available;: but at: least within orie. week cifsampllng. If counts at anyone site exceed 5,000 cell$/rr\I~ then the monitoring frequenc~andassoCiated repoitingat all :sites shalL increase to weekly until all sites show re.sults less than5,OOOcells/ml. or as otherwise agreed with Waikato Regional Council .

.Should monitoring results demonstrate that it would be in the public interest to do so, Waikato Regional CoUncll may require an increase in monitoring frequency for a temporary perioq. Thisrequirement must bernade in writing to the consent holder.

Ix. PrOVision for revision of the monitoring programme on a regular basis.

6.12 The results. of the monitoring programme shall be forwarded to the Waikato RegioMI Council at agreed times, but atleast annually, and .shall include:

• A review of all data collected under the monitoring programme.

• A summary of the monitoring results and a critical analysis of that information.

• A comparison of the data with previously collected data identifying any emerging trends.

• Recommendations on alterations to the monitoring programme.

• Any other issue considered important by the consent holder.

David Hamilton & Associates Ltd Page 61 of61 1 August 2005 ,I

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