Lake Tekapo Research Articles

An assessment of the economic feasibility of the floating PV technology in Aotearoa–New Zealand

Electricity generation from utility-scale solar facilities is projected to grow to between 5 and 16 TWh by 2050 in Aotearoa–New Zealand. The floating photovoltaic (FPV) technology is considered a viable option for the country, because of the good solar resource at existing hydropower schemes. This paper aims to inform the understanding of the economic feasibility of FPV systems through the analysis of specific cases – Maraetai Dam and Lake Tekapo. To do so, the solar resource and FPV outputs are obtained through the modelling of Solargis and using industry standard technical specification. As well as the normal uncertainties associated with (potential) FPV performance evaluations, the influence of water temperature is also considered. The overall FPV output is estimated to be between 1,115 and 1,497 kWh/kWp. Using available Engineering, Procurement and Construction (EPC) costs, the levelized cost of energy (LCOE) metric, for a 10 MW installation, is determined to be between NZ$176 and NZ$237 per MWh, with total electricity generation over 25 years between 263 and 353 GWh. In order to reach the required LCOE value of less than NZ$100/MWh for utility scale generation, the EPC costs will have to be reduced by a factor of 2 to around NZ$1,500/kWp.

A model of ice-marginal sediment-landform development at Lake Tekapo, Southern Alps, New Zealand

ABSTRACT The extent of the Southern Alps icefield in New Zealand is well-constrained chronologically for the last glacial cycle. The sediment-landform imprint of this glacial system, however, offers insight into ice-marginal processes that chronological control cannot. We present the first detailed investigation of sediments along the southwestern shores of Lake Tekapo, South Island. We identify seven lithofacies, from which a five-stage palaeoglaciological reconstruction of depositional and glaciotectonic events is proposed: (i) ice-marginal advance and deposition of outwash gravels in lithofacies (LF) 1; (ii) ice-marginal recession and the development of an ice-contact lake, manifest in rhythmite deposition and iceberg rafting of dropstones (LF 2), followed by a depositional hiatus; (iii) ice-marginal recession recorded in ice-proximal aggradation of glaciofluvial hyperconcentrated flows (LFs 3, 4); (iv) ice-marginal advance documented by glaciotectonic disturbance and localized hydrofracturing, coeval with the deposition of delta foresets and a subglacial diamicton/till (LFs 5, 6); (v) final stages of ice-marginal recession and deposition of outwash gravels in LF 7. Two infrared stimulated luminescence ages were obtained from the glaciolacustrine sediments and, whilst the dating has some limitations, the sediments pre-date both the global and local Last Glacial Maximum. Overall, this sequence, consistent with sediment fills recorded elsewhere across South Island, suggests recurrence of processes from different glacial advances and the role of topographic constraints on maintaining lake positions.

St James and the Good Shepherd: windows on the landscape

Two New Zealand churches completed in the 1930s, St James' Church at Franz Josef/Waiau (James Stuart Turnbull and Percy Watts Rule, 1931) and the Church of the Good Shepherd on the shores of Lake Tekapo (Richard Strachan De Renzy Harman, 1935), feature large plate glass windows behind the altar, affording expansive views of the natural landscape beyond. This represented a significant departure from prevailing ecclesiastical design ideas of the time, with the interior of the churches being intimately connected to the landscape outside, rather than the usual largely internalized atmosphere with any sense of the surroundings limited to light coming through strategically placed decorative or stained-glass windows. It is, however, a design aesthetic that has seldom been utilized in New Zealand since. This paper traverses the history and design of the two churches and their relationships with the landscapes in which they are situated, and concludes that St James' Church provides a heightened religious experience and is a more successful metaphor for the Christian journey.

Seiche Effects in Lake Tekapo, New Zealand, in an Mw8.2 Alpine Fault Earthquake

This study investigates the potential for seismic seiches in Lake Tekapo, New Zealand, triggered by ground shaking from an Mw8.2 Alpine Fault earthquake. Synthetic ground motions are used as a forcing boundary to drive lake water motions by further developing a tsunami simulation model—COMCOT—and coupling it with earthquake simulation model outputs. Our modelling results reveal that lake water oscillations are mobilised immediately by the ground movement and further amplified by cross-lake seiches. Amplitudes of lake oscillations can reach up to 4.0 m in the lake’s narrow southern arm, over 1.0 m along the shore of Lake Tekapo township, and about 1.5–2.5 m along many other parts of the lake shore. Large-amplitude water oscillations quickly attenuate in the first 5–10 min after the earthquake due to their relatively short periods, while long-period oscillations continue for a long time, albeit with much smaller amplitudes. Spectral analysis clearly reveals that the ground motions trigger both fundamental and higher modes in the lake whose oscillation periods are consistent with theoretical estimates. We find that large-amplitude lake water oscillations are better correlated with low-frequency, less energetic ground motion content than with high-frequency large-amplitude ground motions. Ground motion-triggered lake oscillations are large enough to pose potential threat to tourists, residents, boats and infrastructure both in the lake water and onshore near the waterfront. In contrast, vertical co-seismic displacements in the lake area, the conventional mechanism for tsunami generation, are too small to trigger tsunami waves of concern.

The Tekapo Glacier, New Zealand, during the Last Glacial Maximum: An active temperate glacier influenced by intermittent surge activity

Quaternary glaciations have created impressive landform assemblages that can be used to understand palaeo-glacier extent, character and behaviour, and hence past global and local glacier forcings. However, in the southern hemisphere and especially in New Zealand, the Quaternary glacial landform record is relatively poorly investigated with regard to glaciological properties. In this study, a 1 m digital elevation model (DEM) was generated from airborne LiDAR data and supplemented with aerial imagery and field observations to analyse the exceptionally well-preserved glacial geomorphology surrounding Lake Tekapo, New Zealand. We describe a rich suite of Last Glacial Maximum (LGM) and recessional ice-marginal, subglacial, supraglacial, glaciofluvial and glaciolacustrine landform assemblages. These represent two landsystems comprising i) fluted till surfaces with low-relief push moraine ridges; and ii) crevasse-squeeze ridges, ‘zig-zag’ eskers and attenuated lineations. The former landsystem records the behaviour of an active temperate glacier and the latter landsystem, which is superimposed upon and inset within the former, strongly suggests intermittent surge phases. The two landsystem signatures indicate a sequential change in ice-marginal dynamics during recession that was likely to have been partially non-climatically driven. Overall, we present the first evidence of surge-type glacier behaviour in New Zealand.

Tsunami hazard from lacustrine mass wasting in Lake Tekapo, New Zealand

Abstract Lacustrine-tsunami risk from landslides can be significant yet for most locations globally the hazard remains unquantified. Lake Tekapo, in the tectonically active mountain belt of New Zealand's South Island, has been chosen to develop surveying and modelling techniques to assess the hazard from landslide tsunamis. Lake Tekapo is ideal for this study due to the high sedimentation rates, steep surrounds and the proximity to active faulting that indicate a high landslide potential. The shoreline tourist settlement and hydropower infrastructure mean the impact of any tsunami could be significant. In 2016 a survey was carried out to collect high-resolution (1 m grid) EM2040 multibeam bathymetry, high-resolution seismic reflection data (Boomer and chirp) and 6 m long sediment cores. These data reveal a diverse range of sedimentary processes in response to high sediment input and numerous landslides with varied styles of emplacement. For example, a one-off landslide initiated 40 m above the shoreline with debris deposits that have runout onto the lake floor to 100 m water depth contrasts with the Cass River delta on the western shore that has failed multiple times during the lake-basin infilling history. Landslide-generated tsunami scenarios are used to determine the relative hazard at different regions of the lake to guide development of a probabilistic tsunami model.

Hidden conservation vulnerability within a cryptic species complex: taxonomic revision of the spotted skink (Oligosoma lineoocellatum; Reptilia: Scincidae) <br />from New Zealand

The diverse skink fauna of New Zealand comprises 40 described species within the single genus Oligosoma Girard, 1857. Cryptic species are common among New Zealand skinks, leaving numerous species undescribed. We used molecular phylogeny together with morphological analyses to distinguish four species in the spotted skink, Oligosoma lineoocellatum (Duméril & Duméril 1851), species complex. These are O. lineoocellatum sensu stricto, which is confined to the centre of the South Island, O. prasinum sp. nov. from the Lake Tekapo region, O. elium sp. nov. from the northern half of the South Island, and O. kokowai sp. nov. from the northern South Island, Cook Strait, and the North Island. Despite significant genetic differences, the morphological similarity of these species made it challenging to resolve their taxonomic identity. Three of the four species previously recognised as a single, widespread taxon are now recognised as threatened with extinction by a combination of invasive predatory mammals and land use change.

Productivity and composition of perennial lupin pastures in response to six sowing rates, lime application and lupin type at Glenmore Station, Lake Tekapo

This study aims to identify the sowing rate necessary to produce lupin dominant and productive pastures in the New Zealand high country under low-moderate fertility, and a regime of late spring/early summer grazing. Blue and Russell lupin were sown on 12 December 2012 at rates of 2, 4, 8, 12, 16 and 32 kg/ha with cocksfoot at 2 kg/ha, and ± 3 t/ha lime. Low lupin sowing rates (

Mt John Observatory: the first 50 years

Mt John Observatory at Lake Tekapo is New Zealand’s only professional research observatory. It was founded in 1965 as a joint institution of the universities of Pennsylvania and Canterbury, though the American participation disappeared after 1980. Some of the successes of the past 50 years and also the numerous problems that arose are described here. Four telescopes have been established at Mt John, including the 1.8-m MOA telescope in 2004, dedicated to microlensing. Astro-tourism has flourished in the past decade.

Sheep performance on perennial lupins over three years at Sawdon Station, Lake Tekapo

A three-year trial compared the performance of Merino ewes grazing on a perennial lupin pasture with a control flock run predominantly on lucerne pastures at Sawdon Station, Lake Tekapo. At tailing in December, lambing averaged 111% and ewes averaged 58 kg for the lupin pasture, and 105% and 62 kg for the control flock, while lambs averaged 19 kg for both mobs. At weaning in February, ewes and lambs on the lupins averaged 58 kg and 28 kg compared with 63 kg and 31 kg for the control flock, and ewes gained 3.8 kg compared with 5.5 kg from March to mating in May. In September, wool averaged 4.62 kg/ewe for the lupin mob and 4.92 kg/ewe for the control flock, with a mean fibre diameter of 18.5 μm. The average herbage mass on the lupin pasture was 3.0 t dry matter (DM)/ha at the start of lambing in October, reached 7.8 t DM/ha in December and decreased to 3.5 t DM/ha in May. Results support the use of perennial lupins where lucerne fails to thrive on high country farms. Keywords: high country, liveweight gain, Lupinus polyphyllus, Merino

Perennial lupin establishment and yield when sown at five different rates at Glenmore Station, Lake Tekapo.

Abstract The potential for perennial lupins to underpin grass/ legume pastures was the subject of a research programme for merino farmers in areas where more conventional legumes struggle to thrive. A previously uncultivated pasture on an acidic soil, (pH 5.0; Al = 5 mg/kg), and dominated by browntop, sweet vernal and Kentucky bluegrass, was sprayed with herbicide, burnt and top-dressed with 3 t/ha lime on half the area in the autumn prior to direct drilling on 12 Dec 2012. A blue perennial lupin and a multi-coloured (Russell) lupin were sown at 2, 4, 8, 12, 16 and 32 kg/ha and cocksfoot at 2 kg/ha. Yield at four months after sowing had increased with the lupin sowing rate; up to 5.5 t dry matter (DM)/ha at 32 kg seed/ha. The annual yield for the following growth season was greater than 10 t DM/ ha with little response above 8 kg lupin seed/ha. There was a small but inconsistent response to the lime by the Russell lupin. Overall, lupin contributed 79% of annual yield and >90% of the spring yield at sowing rates >8 kg/ha. The sown cocksfoot and resident grasses showed a positive lime response at the lower lupin sowing rates. Key words: Lupinus perennis, L. polyphyllus

The rise to dominance over two decades of Lupinus polyphyllus among pasture mixtures in tussock grassland trials

Abstract In two trials near Lake Tekapo, one started from sown binary mixtures of 14 different legumes, of which Lupinus polyphyllus was one, was cross sown with 16 different grasses, while in the other trial L. polyphyllus and Trifolium hybridum were over-drilled across established swards of previous 25 different grass and legume species. In both L. polyphyllus persisted, increased and spread by seeding in the presence of repeated mob grazing by sheep to become the dominant species over two decades. Keywords: New Zealand, rangeland pasture development, Lupinus polyphyllus, Bromus inermis.

Over-Drilling New Zealand Tussock Rangeland with or without a Previous Legume Phase

A nineteen year trial at Lake Tekapo compared the longer term trends of over-drilling legume and grasses into either previous undeveloped tussock country or following a previous legume phase. Tall oat grass (from summer sowing) and cocksfoot (from spring sowing) were the most successful of the sown grasses. They remained a low proportion of the swards but greater with prior herbicide treatment, sown with an experimental drill giving partial cultivation and with starter nitrogen fertiliser. Perennial lupin became the main species in the previous undeveloped block and was increasing in the previous developed block. The analysis stage considered the inclusion of covariates for contoured location responses as well as treatment effects in such multi-plot field trials on uneven ground.

Effect of biennial spelling from grazing of a high country, moderate input, mixed pasture

A 18-year trial at Lake Tekapo compared changes in proportions of species in a common mixed species pasture under two mean grazing intensities, three seasons of grazing and spelled in alternate years or unspelled. The main species changes related to season of grazing, with the effect of biennial spelling being small and ambiguous, and that of mean grazing intensities slight. Keywords: New Zealand, high country, spelling, pasture development, perennial lupin, cocksfoot

Paleoseismicity and mass movements interpreted from seismic‐reflection data, Lake Tekapo, South Canterbury, New Zealand

A 61 km seismic survey of Lake Tekapo was shot in 2001 to identify tectonic features observed onshore. The survey revealed bedrock highs, lake‐floor offsets, and a series of mass movement deposits, all interpreted to result from tectonic uplift and paleoearthquake events. Fine‐grained sediment within the lake basin, imaged as uniform, regular‐spaced, laminated reflectors, is at least 145 m thick at the southeastern end of the lake. Bedrock highs (>70 m of relief) are found along‐strike of the Irishman Creek Fault and Forest Creek Faults, and are interpreted as long‐term features that are repeatedly raised in earthquakes and lowered by glaciers. Movement on them since the last glacial maximum has offset the lake floor by 10–20 m, consistent with estimated uplift rates on these faults from previous studies. The seismic reflection data suggest that both faults extend into the centre of the lake, terminating against a north‐south‐oriented structure, possibly the Tekapo River Fault. Mass movement deposits are observed within the sediment pile, and we attribute them to paleoearthquakes on local faults or the more distant plate boundary. Using a sedimentation rate of 8 mm/yr, we date two sets of mass movement deposits at 1720 ± 344 yr BP and 2810 ± 562 yr BP.

Reconnaissance sediment and microfossil analyses of a laminated short piston core from Lake Tekapo, South Island, New Zealand

A 2.2 m piston core from the main basin of Lake Tekapo comprises millimetre‐centimetre‐scale alternations of light and dark laminae. Two much thicker layers occur near the base of the core and are interpreted as major slump deposits. Light laminae are predominantly fine silts with low microfossil concentrations. Dark laminae have higher clay, mica, and microfossil content and higher planktic/benthic diatom ratios. These findings are consistent with light laminae being deposited during times of high river flow and high sediment input, the thickness and number forming a proxy for paleoclimate (rainfall, water inflow, and erosion rates), and the dark laminae being deposited by settling out of the water column during periods of low inflow. The distribution of pollen from plants introduced to New Zealand by Europeans, and the inconsistency of dominant pollen types between samples, suggests that the entire sequence is only c. 100 yr old and that couplets of light and dark laminae form more frequently than annually. With appropriate processing, diatoms, spores, and pollen are present in great enough numbers in the dark laminae to be used for paleoclimate reconstruction. Diatoms are predominantly planktic lacustrine forms with some benthic forms sourced from the lake margins. Pollen and spores are derived from local grasslands, montane forest, fell fields, and tussock lands, and from West Coast lowland forest. Palynomorphs are carried over the central Southern Alps by prevailing northwesterly winds, and are deposited in the lake. The presence of fresh‐looking Casuarina and possibly Banksia and Eucalyptus pollen shows that it is likely that some pollen came from Australia. It is believed that the presence and abundance of West Coast derived pollen, particularly Dacrydium cupressinum, and to a lesser extent Ascarina lucida, Nothofagus, and Podocarpus/Prumnopitys species, could be used as a proxy for the intensity and persistence of northwesterly winds.

Resisting Modernism or the Last Gasp of the Arts and Crafts?: Church Building in Canterbury and North Otago in the 'Thirties

The dominant historical narratives of twentieth-century architecture present the 1930s as the period during which Modernism's claim to be the architectural style of the century was consolidated and when the new architecture began to spread across the globe. In New Zealand, as in the rest of the world, this master narrative has tended to obscure the significance of buildings constructed in more traditional styles. The five New Zealand buildings included in the RIBA's Centennial Exhibition, International Architecture 1924-1934, were not, however, the latest examples of Modernism in this country, but relatively conservative designs, including Cecil Wood's Arts and Crafts inspired St Barnabas's Church at Woodend (1932). Wood's building forms part of an extensive group of small country churches built throughout Canterbury and North Otago during the 'thirties. These include Wood's St Paul's, Tai Tapu (1930-31) and Herbert Hall's St David's Memorial Church at Cave (1930), although by far the best know is RSD Harman's Church of the Good Shepherd at Lake Tekapo (1935). These small, unpretentious churches, many built with assistance from a government fund initiated to stimulate the construction industry, made use of modern materials, especially reinforced concrete, but their mode of expression remained conservative. They were often embellished with furnishings executed in the traditions of the Arts and Crafts movement. In most cases these churches were important statements of local identity while at the same time expressing the diverse cultural origins of those who built them. In style they were invariably Gothic yet within that dominant idiom considerable stylistic diversity was achieved. For both architects and their clients Modernism, with its emphasis on internationalism and the machine, was unable to express the rich veins of meaning which such buildings were required to embody. Yet as expressions of the uncertainties of the time, their conservative aesthetic values, their reassertion of pioneering roots and of an enduring local identity were as significant as Modernism's confident assertion of a better, essentially urban, future. At a time when the approaching Centennial events of 1940 was stimulating a reassessment of the country's past, these buildings also acted as powerful statements of consolidated achievements.

Enhanced dust deposition by trees recently established on degraded rangeland

Results from 2 years of dust deposition monitoring in a 10‐year‐old Pinus nigra plantation near Lake Tekapo are presented. They show that recently established plantations significantly enhance dust deposition rates. This could reverse a cycle of soil loss and enhance vertical accretion of soil, which would provide more options for future land use. However, observations indicate that even under such enhanced conditions for soil formation, it would take several thousand years to replace the soil lost to erosion since European farming practices were first introduced to the northern section of the Mackenzie Basin.

Observations of Anti-winds in a Deep Alpine Valley, Lake Tekapo, New Zealand

This paper presents observations of summertime anti-winds monitored under ideal conditions in the Lake Tekapo hydro-catchment situated in the central Southern Alps, New Zealand. Onset and cessation of anti-winds was observed to coincide with the change in phase of the surface limbs of thermally generated valley and mountain winds under settled anti-cyclonic conditions. Anti-winds were best developed in the early morning before surface heating and associated convective mixing of the valley atmosphere began to mask the boundaries between the surface based limb of the mountain-valley wind and the corresponding anti-wind. By mid-day, the anti-valley wind exceeded the height of the surrounding ridgeline and became embedded in the topographically channeled gradient wind. Observations presented here have both theoretical and applied implications with regard to the development of thermally generated wind systems in deep alpine valleys, and their role in the dispersion of air pollution.

Numerical simulations of wind and temperature structure within an Alpine lake basin, Lake Tekapo, New Zealand

High-resolution numerical model simulations have been used to study the local and mesoscale thermal circulations in an Alpine lake basin. The lake (87 km2) is situated in the Southern Alps, New Zealand and is located in a glacially excavated rock basin surrounded by mountain ranges that reach 3000 m in height. The mesoscale model used (RAMS) is a three-dimensional non-hydrostatic model with a level 2.5 turbulence closure scheme. The model demonstrates that thermal forcing at local (within the basin) and regional (coast-to-basin inflow) scales drive the observed boundary-layer airflow in the lake basin during clear anticyclonic summertime conditions. The results show that the lake can modify (perturb) both the local and regional wind systems. Following sunrise, local thermal circulations dominate, including a lake breeze component that becomes embedded within the background valley wind system. This results in a more divergent flow in the basin extending across the lake shoreline. However, a closed lake breeze circulation is neither observed nor modelled. Modelling results indicate that in the latter part of the day when the mesoscale (coast-to-basin) inflow occurs, the relatively cold pool of lake air in the basin can cause the intrusion to decouple from the surface. Measured data provide qualitative and quantitative support for the model results.