By Susan Harris*
Back in the day, my first real job was as a government scientist in the Water and Soil Division of the Ministry of Works and Development (MWD). We scientists collaborated with dam engineers from Power Division to plan new hydro power developments. The scientists worked on the water supply modelling, environmental, and social impacts of projects, while the engineers worked out how to build a safe dam and deliver power to the national grid.
Now, as everyone knows, hydro power stations need water to generate electricity. The ultimate source of the water supply to Lake Onslow 2.0 will be snowmelt from Mount Brewster and its surrounding mountain terrain and glaciers in Mount Aspiring National Park. Snowmelt water flows from the mountains into Lakes Wakatipu, Wanaka, and Hawea and then down the Clutha/Mata-Au River to Lake Onslow 1.0.
The Clutha/Mata-Au catchment is the biggest in New Zealand. Snow and ice melt comprises at least 75% of its water supply (ORC 2023). We learn from Taylor Bardley 2019 in their paper: A Hydrological Drought Index for the Clutha catchment, New Zealand that:
“It has a large seasonal flow variability with large spring and summer flows and very low flows in winter. ….The mountainous South Island topography to the west means that a large part of the catchment is in a rain shadow and is regularly subject to long periods without any significant precipitation, similar to many other rain shadow catchments globally….The main part of the catchment, from the outflow of the lakes to Roxburgh, is in a rain shadow with rainfall as low as 325 mm per annum [almost desert levels] in the Springvale area near Alexandra…..”
The authors’ upper and mid-Clutha drought index from 1930-2014 shows us that only three years – 1979, 1980, 1983 – were classified as ‘wet’ years. Out of the total 84-year record, 47 years (56%) experienced mild to extreme drought conditions. So we know there is already a drought problem in the catchment, and that it is already highly modified by competing water uses including irrigation takes, rural and domestic water supply takes, and other major hydro dam developments.
In addition, over the past ten years there have been an increasing number of alarming reports about the scale and speed of glacier melt and snow and ice retreat from New Zealand mountains, in common with similar mountain environments around the world. A media article last week reported on NIWA's 2022 preliminary findings that snowmelt and glacier retreat is accelerating in New Zealand. The Brewster Glacier in particular is disappearing fast.
The volume lost from Brewster during 2016-2019 was about equal to the basic drinking water requirements for all New Zealanders for those three years NIWA 2020. That’s a phenomenal amount of water that won’t be coming back. The Brewster Glacier may be gone completely inside the next decade or two. Indeed, based on current trends, almost all of New Zealand's glaciers could be gone by the end of this century. And that means way less water supply for the nation.
So I searched through the public information provided by the Ministry of Business, Innovation and Employment to see if I could find proof that there will be enough future water supply to fill and operate the dam. One would think that this would be the first step with any 21st Century hydro power development, especially one dependent on water supply from disappearing glaciers. All I could find was a presentation outlining project phases. None of the phases appeared to address this fundamental question.
Then I was provided with the 429-page business case for Lake Onslow 2.0 - New Zealand Battery Project: Progressing to the Next Phase (MBIE 31 March 2023). Looking at the Executive Summary, security of future water supply is not mentioned, nor is it included in the 12-point Multicriteria Analysis used for the Treasury’s critical success factors framework. The ‘dry year’ problem discussed briefly does not include a note on existing drought problems nor a trend analysis of future required water supply volumes for the dam.
In fact in the entire 429-page tome, there are only three small sections in Appendix E totalling 246 wordsthat addressinflow assumptions and future climate change effects on Lake Onslow 2.0. These sections contain five fundamental errors and omissions:
1) Forecasts for future flows are based on back-casting historical flows from 1932, which means the project proponents assume future flows will remain the same as they were since 1932
2) Climate change is not regarded at all seriously with the comment: “While the climate probably has changed since the 1930s, and will change further going forward, we used the full range of inflow sequences back to 1932….”
3) Climate change impacts on flows are predicted using an estimate of a 25% reduction in snowmelt to 2050, when NIWA measurements indicate that a 50% estimate is probably more appropriate. The observed acceleration in climate change impacts on glacier systems reported by NIWA is not mentioned at all
4) Remarkably, large increases in hydropower lake storage levels and spill are projected between 2020 and 2050, 17% at Lake Hawea (Clutha/Mata-Au), which doesn’t make sense when the headwaters – 75% of supply – are melting away at pace
5) No historical flow trend analysis is presented (are river flows decreasing over time?), neither are any snow and ice mass balance calculations (how much water is gone and won’t be coming back?), nor annual hydrological modelling that includes drought indexing and the future demands of other users of water in the catchment.
This report would not have passed muster at MWD. These issues need to be urgently addressed before another $70 million is spent on the project. What assurance do tax payers have that Lake Onslow 2.0 won't end up like Lake Mead, built using data from an unusually high flow year, on an assumption that the past predicts the future, ending up with storage levels too low for power generation, or worse, a screamingly expensive 1.5km-long dry hole in the ground by the end of the century?
Where are the numbers to assure ordinary tax payers that Lake Onslow 2.0 won't become a casualty of climate change? The presented modelling work has academic assumptions and real world data gaps that are too broad to be acceptable for a project with this huge price tag. The project proponents need to get out there and actually measure reality.
And where is the forward planning to make sure all our mountain-fed hydro power schemes will be secure throughout the rest of this century? Otherwise as a nation we'd better look to switching to more solar, wind, and geothermal power. After all, $16 billion is enough to retrofit every house in New Zealand with solar panels.
And what about New Zealand's water futures? Who is looking into that? This is something that the Climate Change Commission and Parliamentary Commissioner for the Environment could be tackling on behalf of us all. The trends are obvious and very alarming according to NIWA's glacier monitoring data. New Zealand needs to act now to secure its water futures into the 21st Century.
*Susan Harris is Principal Scientist at GreenXperts Limited, a New Zealand-based sustainability consultancy involved in numerous carbon and land management projects. Susan was on the science team that helped the New Zealand Government create the New Zealand Emissions Trading Scheme. Susan worked on emission factors with other colleagues at that time.
58 Comments
Yes , we could retrofit every house in NZ with solar panels ... or we could spend that $ 16 billion on a single project , Lake Onslow ... based on a MBIE report with numerous errors & omissions ...
... one can only pray Labour lose on October 14 or Onslowbuild will be the track taken ...
Gummy if every NZ household had a solar panel then in summer this would produce twice as much electricity as winter because summer days are twice as long as winter days. Yet peak demand for electricity in NZ is in winter. So how would all that solar help? And what would we do with all the surplus electricity in summer?
Even in summer, peak electricity demand is morning and evening, when very little is happening on your panels.
To make it a fair comparison you'd need to spend at least as much on storage, and besides being in huge demand, lithium batteries have a short and fixed life span.
I think that is the whole point of pumped storage. It creates a place to store all that excess green energy which is by it's nature irregular and unpredictable, and then allows us to draw down this energy when we need it and our conventional green generation sources are not producing much.
Having said that, this talk of pumped storage is irrelevant with the current structure of our power system. It would be relevant if significant amounts of renewable power was wasted. But is this the case? I think that wasted renewable energy principally takes the form of opening the spillway gates at the Dams. This should only happen very infrequently when we face the threat of flooding. So essentially most if not just about all renewable energy is usefully used. (If it isn't then the first and most urgent thing to do is to make sure that is manged this way) We have about 20% of our electricity generated from non renewable fossil fuels. The variation in the difference between supply and demand is smoothed out by modulating the fossil fuel generated electricity varying the amount of hydro electricity geration.
In my mind pumped storage only becomes relevant when we have a lot more renewable energy by way of solar and wind, and we exceed the capacity of the hydro storage lakes to store sufficient energy to smooth out the short term and long term variation between supply and demand.
At some point in the future this will all become relevant I hope, so it is important to think about it now as these sorts of projects have very long lead times.
What I haven't seen and I think is crucially important, is modeling to predict how the current system can be managed and optimized so that non renewable generation can be significantly ramped down, replaced by wind and solar, and the existing hydro system used to act as the temporary battery. (similarly managing the charging of EV car batteries) We should also be seriously thinking about adding more hydro generation, eg upper and lower Clutha plus the lower Waitaki. Probably lower cost than Onslow and provide significant extra power as opposed to just storing it. The point when this sort of arrangement cannot cope with the volatility is the point when we need Pumped storage.
The removal of the generation assets from government control and turning them over to a "competitive" market system (sick joke) has made any rational development of the generation system as above, a nearly impossible nightmare. The government has totally squandered it's opportunity to return these assets to state control with any hope of rational development.
There is currently more emphasis on new battery technologies being made by many of the OECD countries around the world than on water storage as a means to store energy.
So why should we waste money on such a scheme. Just but new battery technology in 5 - 10 years to solve the energy storage issue, and put the batteries near where they are needed (Auckland/Hamilton etc). Remember 25% of our electricity energy is lost in transmission lines. So a 100MW system in central Otago will lose 25MW getting the power to Auckland.
Does this make economic sense?
I was just reiterating the point made by the author ... demonstrating the scale of the money about to be wasted on the Onslow2 project ...
... personally , I'd sooner see our geothermal power production ramped up by multiples ...
Plus , get back into Nat Gas exploration ...
Gummy
You are just like one of the knockers back in the days of Muldoon's Think Big who reckoned it was cheaper to put LPG/CNG in every car than build those really expensive energy plants such as synthetic-petrol plant at Motuni, the methanol plant at Waitara, and the expansion of the Marsden Point Oil Refinery. But, no; "these will provide ongoing assurance of our energy for ever, ever more" said Muldoon and Bill Birch.
So, um, um . . . yes. OK, then. Now all closed. Yes, it would have been cheaper and better to put those LPG/CNG units in. :(
Onslow 2 is a dog of an idea ... the same $ 16 billion could be diversified around solar / wind / and new geothermal plants to give us far far better bang for our buck ...
...can't follow all that other stuff you're referencing ... it's nothing to do with me ... I was just a kid then , find an adult to blame ...
Retrofit and include battery storage to sell excess power into to be purchsed back if needed at same cost no need to dig hole on mountain when we can engineer batteries to be installed near where power use exceeds production.
Also think about 10years time how much better will battery tech have evolved.
Disappearing glaciers does not necessarily mean the volume of water flowing down rivers decreases. What it means is less precipitation is snow and less precipitation is stored in the higher elevated parts of water catchments in the form of ice (glaciers).
Disappearing glaciers will therefore increase the variability of water flows. So the likelihood of hydro dams both having to spill water during floods and having insufficient water flow to generate electricity during 'dry periods' will probably increase.
If the Onslow scheme does proceed these factors will not affect its operations. The amount of water it takes from the Clutha to pump up to the Onslow storage dam is only a small fraction of Clutha's water flow.
Also, the Onslow scheme would only take water from the Clutha to pump up to Lake Onslow when wholesale electricity prices are low, which is likely be when hydro generators are producing electricity i.e. during high flow periods. The scheme would then release the water back down to the Clutha to generate electricity when electricity prices are high, which is likely be during low flow periods. So Onslow would have a moderate evening out of the lower Clutha's river flow rate.
It is best to think of Onslow as a very large long lasting battery (or even the electricity equivalent of our ancestors storing food and wood for a possible harsh winter) rather than a standard NZ hydro dam like what MoW built in the past.
In some ways Onslow is similar to glaciers - it being a store of water high up in the water catchment which therefor has high potential energy. But in Onslow's case it takes energy to lift the water (unlike rain and snow) and for Onslow we get to choose when to release the potential energy rather than being dependent on natural cycles of rainfall, freezing and melting.
If Onslow or any other pump hydro scheme is 80% efficient this means it needs to buy electricity for pumping duties at a low price x. Then after it has stored the water at an elevated height - when it generates electricity - it must sell this generation for a higher price of x plus 25% just to break even from a efficiency loss operating cost perspective. It could recoup other operating costs (which are minimal) and capital costs by having a greater price spread, or it could recoup the capital costs by a security of supply line charge (or the government could subsidise the scheme).
NZ's wholesale electricity prices over time vary by much more than 25%, so pumped hydro only being 80% efficient is not a deal breaker. High capital costs as discussed below is an issue though...
Thanks for the sensible comment. If there is going to be climate change then we will have to find ways to mitigate it- for any project that is built going forward.
If we are going to tackle carbon emissions we will have to electrify as many of our machines and transport vehicles as possible and provide an adequate and continuous supply of electricity for these machines and vehicles. Putting solar panels on every roof in NZ is a good idea to increase electrical output but not sufficient to ensure an uninterrupted supply. So some form of storage capacity is needed.
What I see in this article is a lot of misleading figures as a reason for why we can't do something as a nation, but no genuine solution to replace the proposed project.
If we don't do anything to solve the problems that we face as a nation, rather spend large amounts of money on consultants in a never ending talkfest, then we will end up with no money, few problems solved and a rich bureaucratic elite strangling the lifeblood out of the nation.
As the rich bureaucratic elite gets more and more money and less is spent on essential infrastructure you eventually end up like South Africa with load -shedding, industry that can't get sufficient electricity to run factories and a politically astute but technically incompetent elite that refuses to do anything practical because they don't know how to make anything work anymore.
The problem with Onslow is not that it can be easily replaced with overbuilding geothermal, wind or solar as the author and others say (I don't think there are 1000MW geothermal schemes ready to be developed as Gummy thinks there is). NZ does though have lots of largescale consented yet unbuilt wind farms. The problem is the market structure (Bradford reforms) does not give a monetary value to security of supply - in fact it does the opposite. The big generators who have the consents are incentivised to keep the market undersupplied so they can profiteer from corning the market. Ensuring the dry-year risk continues - where hydro that typically supplies 57% of the market - periodically has to reduce supply is an important part of their pricing (profiteering) strategy.
When Onslow was first proposed a few years ago it made perfect sense. Government agencies could borrow cheaply - lets say 1% and the scheme looked like it could be done for $5bn. So the debt costs would have been $50m a year. Divide that by 2m households and it would have been an extra $25 a year added to the power bill. Which would have gauranteed security of supply and prevented the large generators from continuing with their strategy of undersupplying the market. So the cost was quite small compared to the benefits.
But the scheme when investigated more thoroughly will now cost three times the original guesstimate and more importantly government borrowing costs is now five times greater. So the debt cost is not $25 per year per household. It could be something like $375.
There is an alternative to Onslow that the NZ Battery project could consider that wasn't available a few years ago. That the government uses Huntly to burn carbon neutral biofuel as a 'battery' when hydro cannot supply its usual amount of generation. There has been considerable advances with the likes of torrefied wood pellets which indicates this could be viable. If the government was worried about security of electricity supply (which I think is the rationale for the NZ Battery Project) and wanted to prevent the large generators from cornering the market it could have a strategic biofuel supply - both in the form of finished pellets, but also in the form of standing forests that in times of need - felling, processing into pellets, and transport can be ramped up. It is possible the capital and operating costs of this option could be less expensive than Onslow.
Looking further ahead. It looks like NZ can burn biofuel and sequester CO2 down in geothermal fields which should make the economics of biofuel much more affordable and create another route to NZ decarbonising its economy.
Regardless of the merits of Onslow Susan is right with respect to the data as it appears to be woefully deficient for a project of this scope
To many policy wonks and treasury "experts" involved and not enough scientific analysis being undertaken -which is all part of a trend and shows up as time and cost overruns along with white elephants
and reports being prepared for ministers or bureaucrats should be available in real time for everybody - it could improve the decision making immensely
Yet Susan is part of the Wellington consultancy gravy train and her scientific and technical understanding of the proposed Onslow scheme as demonstrated by this article is poor.
The overall generation capacity of a normal hydro scheme is not related to snow melt from glaciers as Susan claims. It is related to the annual rainfall rate of the catchment area above the hydro scheme. This is likely to change due to climate change but not necessarily related to dissapearing glaciers. It is quite possible in the future climate change means the Southern Alps has more rain, less snow, smaller glaciers, and an overall increase in river flows. It is also possible climate change increases rainfall (due to an increase in extreme rainfall events) and there is an increase in the frequency and severity of dry hydro periods - which is the problem Onslow is trying to solve.
Regardless of if rainfall increases or decreases, Onslow is not a normal hydro scheme - it is a storage scheme which can double the stored energy of the rest of the hydro network from 6 to 12 weeks - meaning NZ will not have to cut electricity demand or find additional generation capacity when we have a periodic supply constraint from the a dry hydro year. Because Onslow is a storage scheme that takes water from the Clutha near Roxborough and returns the water to the Clutha, and the Clutha is NZ's highest water volume river, and the Onslow scheme requires relatively little water (the stored energy is coming more from the height drop rather than the water flow volume) so the possibility of Onslow facing a Lake Mead situation of insufficient water for storage duties is basically zero. Susan for some reason is trying to scare readers on an issue that has no evidence basis.
.Surely nobody believes the cost estimate. Were it ever built, it would cost many times more than the current figure.
As has been suggested elsewhere, in terms of bang for bucks, getting every home properly insulated would deliver economic, social and health benefits for a fraction of the cost.
I still find it hard to believe just how incompetent this bunch really are.
Except for the initial fill to raise Lake Onslow, Onslow pumped storage would not be a consumer of water from the Clutha River other than an on-going evaporation loss of about 1 cumec. Given that we know the Clutha is New Zealand's largest by discharge, it is not about to disappear any time soon and should be easily able to handle the 1 cumec loss. As others have mentioned, pumping will tend to be at times of higher flow, with generating at times of low flow. So Onslow in operation will to some extent offset future periods of low Clutha flows.
I agree Earl. Clutha river is sourced in the Southern Alps, with many metres of rain a year, not in the area of the Onslow catchment, which is indeed a dry area. Changes to snowpack only redistribute the water in the river between seasons, they don't reduce the amount of annual water in the river. Glaciers only contribute a tiny amount of annual flow into the Clutha catchment (don't know what "ORC 2023" is). The Clutha river flow is projected to get higher over the next few decades, with no change in dry periods (Purdie, J. (2022) Modelling climate change impacts on inflows, lake storage and spill in snow-fed hydroelectric power catchments, Southern Alps, New Zealand. Journal of Hydrology (NZ) 61 (2): 151-178, Collins, Daniel 2020: New Zealand River Hydrology under Late 21st Century Climate Change, Water 2020, 12, 2175; doi:10.3390/w12082175) - Dr Jen Purdie, Climate and Energy researcher, University of Otago.
Not to nit pick too much. I have a problem with this statement
"The scientists worked on the water supply modelling, environmental, and social impacts of projects, while the engineers worked out how to build a safe dam and deliver power to the national grid."
To my mind the nearly all the input is from engineers. Water supply modelling, predominantly engineering. Environmental, largely engineering.
Social impact, very unlikely engineers.
Very little input from scientists, except social sciences.
"I was provided with the 429-page business case for Lake Onslow 2.0 - New Zealand Battery Project"
This must have been an OIA request. A case of on the need to know basis and the public don't need to know. I searched the NZ Battery project website and can't locate the project report. I expected it to be on the front page as a downloadable pdf
Key point made in many posts simplified, onslow is not using any extra water.
I think Onslow should be built, but maybe not to the scale planned. Have any studies been done on different size dams ? Too many eggs in one basket for my liking. And I'd like to see more study into west coast river catchments, pumped to east coast storage.
My understanding of the decline in water levels at Lake Mead is that it is mainly due to excessive and increasing drainoff by the big water users (mainly California), rather than low inflows in the catchments. A similar situation to groundwater on the Canterbury plains.
The official drought map seems to confirm this
I've been watching lake Mead levels on and off for the last year. What is usually glossed over is the increase in agriculture demand and population growth over about 80 years ago.
MSM conveniently blame CC. Lake Shasta a Californian reservoir/dam/lake whatever you like to call it has filled to about 80% over the last month or so.
Now the floods and heavy rain also blamed on CC resulting in a number of Californian water storage facilities being filled up
Its a win-win for CC because you can blame it on droughts or floods, even if the actual evidence points to predominantly natural variability.
I have searched the report "new-zealand-battery-project-indicative-business-case-v1-10-and-appendices-february-2023" with the keyword iwi. Have got to pdf pg 58 and so far without mentioning co-governance, the document is full of it. Quite blatant kow-towing to Maori.
One of the sentences, "Many of these schemes were developed in a way that is inconsistent with tikanga,
such as the mixing of waters from different rivers for the Tongariro Power Scheme."
Sorcery/witchcraft that has no place in the modern world.
But economics is entirely acceptable. Hahaha.
Before I knew anything about Tikanga I remember as a kid hearing about the shifting of water from the Whanganui to Waikato and while as an engineering feat I thought awesome, it left a hollow feeling. That's a massive ecosystem change. The hydro project based around Ruahihi in the lower kaimai is similar but the negative effects on the river systems is obvious and massive.
Yet another ill thought out and indeed hiding the facts of a scheme that has a very dubious outcome.
We have become accustomed to the shear waste that this government is guilty of and it sis time all of their capital expenditure projects were frozen until the outcome of the election is known.
What are we now -up to $80billion borrowed and no clear pathway to paying it back - but it will surly shackle the next government.
Like Susan I'm concerned about ongoing ablation of New Zealand's glaciers and the true merits of the proposed Lake Onslow stored energy scheme.
However the reference to the Brewster Glacier to further this argument is spurious. While the Brewster Glacier is indeed located within Mt Aspiring National Park, the meltwater from the glacier flows west down Pyke Creek, then joins the Haast River which flows northwest to meet the Tasman Sea at Haast. No part of the Brewster Glacier ever flows down the Clutha River, and hence is not available to become part of the Lake Onslow scheme.
The argument may be reasonable, but the example given is a poor choice!
Looking at Google road photos over the years, doesn't seem to be a huge runoff anyway. Mostly be rain on that side I would say. Could be worth pumping over Haast pass into lake hawea.not sure on the rules been a national park, but they put a highway through there.
There are many problems with the Onslow project such as efficiency losses and evaporation losses. However my principal reservation is that the electricity market will have to be redesigned to make the project possible.
If the project needs to buy the electricity necessary to fill the reservoir, it will be a demand that by market design will increase the local price meaning the electricity will be more expensive than in the counterfactual case. When the reservoir is producing electricity it will be a supply that reduces the local price . That is, the very existence of the project will deeply reduce its viability as a result of the commercial interaction with the current market. Where is the analysis of commercial viability after modelling to include these market interaction effects?.
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