Auckland Dam Levels

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jpoc

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#2800119 23-Oct-2021 17:56

networkn:

Pictures I saw of the dams and the water levels in rivers and streams 6 months ago didn't look exagerated. We are at 94% now better and better by the day.

Just when I want a day of decent weather to do lawn maintenance.

Sure the low levels were honest but when this all kicked off (more than 6 months ago), they were low at the expected minimum part of the cycle and had always then been on a rising trend from that time of the year.

Suppose that we had no extra water from the Waikato, no water use restrictions and lower than normal rain, what would have happened?

The water levels in the dams would have risen. There was never a danger that the city would have run dry.

RunningMan

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#2800124 23-Oct-2021 18:05

jpoc:

Sure the low levels were honest but when this all kicked off (more than 6 months ago), they were low at the expected minimum part of the cycle and had always then been on a rising trend from that time of the year.

According to this, it's 17 months, and water levels were at a 25 year low. Suggests it was a lot more (less?) than a normal expected minimum level.

networkn

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#2801078 25-Oct-2021 21:47

jpoc:

Suppose that we had no extra water from the Waikato, no water use restrictions and lower than normal rain, what would have happened?

The water levels in the dams would have risen. There was never a danger that the city would have run dry.

Not sure I agree with your second comment, but the only way to know, was the reason I started the thread and was the original question of the topic.

I guess if you take the amount of water we have gotten from the Waikato over and above what we got before, and somehow could calculate water use normal vs restricted for the time the restrictions were in place, then you'd have the answer I guess, but I am going to hazard a guess it's a lot more than 10% which means, without the measures, we could have been in some trouble, especially since winter was predicted (and started) very very dry indeed.

Scott3

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#2801959 27-Oct-2021 13:44

In terms of the overall situation Auckland faced, in short faced an very high return period drought.. 35% of normal rainfall in key catchments.

Meteorological projections a the time, were predicting a 1 in 1000 year drought.

https://www.newshub.co.nz/home/new-zealand/2020/04/auckland-on-track-for-one-in-1000-year-drought.html

From an engineering perspective, There was little point in overbuilding our water supply infrastructure to handle a 1 in 1000 year event. Much more economical outcome to design for say 1 in 100, and just scramble to respond to more rare events as we have done (Build new capacity, use restrictions etc.)

Should note that Auckland is not especial short of water sources - evidenced by the fact we had decommissioned a bunch of smaller sources as it was more economic to use large scale one's. - these got re-commissioned over the last couple of years.

With regards to the Waikato take consents, there was a bit of an issue here - Auckland application had a many year old application that had yet to reach the top of the queue for processing. - I don't think the shortage was hyped to get the consent, but watercare did go ahead with the build of more treatment capacity without the consent, in order to put pressure on the authorities with this regard.

mattwnz:

SATTV:

.....

There is no need for there to be any water restrictions at the moment, but I still think that new builds should have 10 - 25000 liters of storm water storage, even if it is used to just flush the loo there is not the need to have chlorinated & fluoridated water go to the poo ponds.

Yes there would need to be a small electric pump and you could have a bypass should you run out of tank water.

We submitted this to our council as part of the district plan update when submissions were called. So all new houses being built must install a 10,000L underground tank for watering gardens and toilets. Some developments around NZ do require this. The council however weren't interested, despite having water shortages and restrictions each year, and a rapidly growing towns. Councils just don't seem to want to be proactive in NZ.

There are good reasons that Auckland dos not mandate 10,000L rain water harvesting tanks for new builds:

Costs $$$ - The tank alone is about $11k Example. Plus Civil works, pump, plumbing (incl dual plumbing systems in house), electrical etc... Auckland already has a housing affordability issue which this would worsen.
In line with the above, generally ROI isn't great. Note that in Auckland wastewater makes up the majority of most people's water bills. For last month mine was $47.77 for fresh water, $85.49 for wastewater. (note that wastewater use is calculated off fresh water use, so people with rain water harvesting systems wither need to go on the un-metered plan ($63.08 a month, or have a meter on the discharge of their rain water system).
A key cost parameter of the system is maximum treatment plant throughput - to deal with high demand in the hottest, dries time of year. - rain water harvesting systems most likely will have run dry then, so contribute nothing in terms of decreasing this peak, but while decreasing demand at times where treatment capacity is plentiful, and hence financial contribution to the system.

As a side note, many new builds already have storm water detention tanks. (to allow a higher percentage of non permeable surfaces & hence denser development than would otherwise be allowed to avoid overloading the storm water network. These need to sit empty (or at least the detention portion of a combined storm water detention / rainwater harvesting system) so that they have capacity available to buffer rainfall. generally they are fully passive systems - rain water in the top, and a skinny pipe that will mean it takes several hours to drain the full tank.

qwertee

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#2801965 27-Oct-2021 14:15

@networkn

When I initially read your topic I thought you were cussing the Covid lockdown levels in Auckland 😀

mattwnz

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#2802025 27-Oct-2021 14:37

Scott3:

In terms of the overall situation Auckland faced, in short faced an very high return period drought.. 35% of normal rainfall in key catchments.

Meteorological projections a the time, were predicting a 1 in 1000 year drought.

https://www.newshub.co.nz/home/new-zealand/2020/04/auckland-on-track-for-one-in-1000-year-drought.html

From an engineering perspective, There was little point in overbuilding our water supply infrastructure to handle a 1 in 1000 year event. Much more economical outcome to design for say 1 in 100, and just scramble to respond to more rare events as we have done (Build new capacity, use restrictions etc.)

Should note that Auckland is not especial short of water sources - evidenced by the fact we had decommissioned a bunch of smaller sources as it was more economic to use large scale one's. - these got re-commissioned over the last couple of years.

With regards to the Waikato take consents, there was a bit of an issue here - Auckland application had a many year old application that had yet to reach the top of the queue for processing. - I don't think the shortage was hyped to get the consent, but watercare did go ahead with the build of more treatment capacity without the consent, in order to put pressure on the authorities with this regard.

There are good reasons that Auckland dos not mandate 10,000L rain water harvesting tanks for new builds:

Costs $$$ - The tank alone is about $11k Example. Plus Civil works, pump, plumbing (incl dual plumbing systems in house), electrical etc... Auckland already has a housing affordability issue which this would worsen.
In line with the above, generally ROI isn't great. Note that in Auckland wastewater makes up the majority of most people's water bills. For last month mine was $47.77 for fresh water, $85.49 for wastewater. (note that wastewater use is calculated off fresh water use, so people with rain water harvesting systems wither need to go on the un-metered plan ($63.08 a month, or have a meter on the discharge of their rain water system).
A key cost parameter of the system is maximum treatment plant throughput - to deal with high demand in the hottest, dries time of year. - rain water harvesting systems most likely will have run dry then, so contribute nothing in terms of decreasing this peak, but while decreasing demand at times where treatment capacity is plentiful, and hence financial contribution to the system.
As a side note, many new builds already have storm water detention tanks. (to allow a higher percentage of non permeable surfaces & hence denser development than would otherwise be allowed to avoid overloading the storm water network. These need to sit empty (or at least the detention portion of a combined storm water detention / rainwater harvesting system) so that they have capacity available to buffer rainfall. generally they are fully passive systems - rain water in the top, and a skinny pipe that will mean it takes several hours to drain the full tank.

That is a minimum of 10,000L, so may make more financial sense to go bigger. Considering most new build are are probably the best part of a million with land, probably a lot more in Auckland, even $10k is probably less than 1% of the cost. There are new subdivisions that already require them. If building in a earthquake area, there are often extra build costs for deeper piles etc that can exceed this too. In Australia I have seen them build the tanks into the facade of the house, to make better use of space.

I wasn't aware of councils charging for wastewater, as isn't that what the rates are for? But probably makes sense in Auckland where you can have a lot of people living in single dwelling or apartments. But basing it off fresh water use isn't great, because many people use water for watering their garden so it never goes into the waste water system.

neb

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#2802049 27-Oct-2021 15:12

mattwnz:
That is a minimum of 10,000L, so may make more financial sense to go bigger. Considering most new build are are probably the best part of a million with land, probably a lot more in Auckland, even $10k is probably less than 1% of the cost.

That leads to another problem: Size. A 10,000L tank is enormous, and since pretty much every new build has nothing more than a slim mowing strip between your bedroom window and the neighbour's living room window so they can cram as much as possible into as little space as possible, where would you fit all of these giant tanks? We put a 2,000L under the house as part of the rebuild (slimline up against the walls) and that's already a fairly big thing, but once you get to putting water storage into spaces where it'll fit you're looking at 1,000L tanks at most. We vaguely considered burying a 1,000L under the path that comes down to the house but that's going to be a ridiculous cost for a relatively small amount of storage.

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mattwnz

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#2802062 27-Oct-2021 15:41

neb:
mattwnz:

That is a minimum of 10,000L, so may make more financial sense to go bigger. Considering most new build are are probably the best part of a million with land, probably a lot more in Auckland, even $10k is probably less than 1% of the cost.

That leads to another problem: Size. A 10,000L tank is enormous, and since pretty much every new build has nothing more than a slim mowing strip between your bedroom window and the neighbour's living room window so they can cram as much as possible into as little space as possible, where would you fit all of these giant tanks? We put a 2,000L under the house as part of the rebuild (slimline up against the walls) and that's already a fairly big thing, but once you get to putting water storage into spaces where it'll fit you're looking at 1,000L tanks at most. We vaguely considered burying a 1,000L under the path that comes down to the house but that's going to be a ridiculous cost for a relatively small amount of storage.

The problem with the way some urban intensification is occurring, green spaces are limited. The governments changes probably make this worse. In some cities in NZ, they require a minimum circular diameter of space for outdoor living, which potentially could be used for an underground concrete tank. A 10,000L underground tank is about 2.4 metre diameter, we got one installed for gardening as it was a requirement on the covenant . It has never run dry yet. It was a couple of years ago but was well under $10,000 all installed. Also roof tanks and wall tanks are possible with the right sorts of tanks. This is a house using tanks to the extreme. https://www.architectureanddesign.com.au/news/how-far-would-you-go-for-sustainability-water-tank

Scott3

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#2802115 27-Oct-2021 17:19

mattwnz:

That is a minimum of 10,000L, so may make more financial sense to go bigger. Considering most new build are are probably the best part of a million with land, probably a lot more in Auckland, even $10k is probably less than 1% of the cost. There are new subdivisions that already require them. If building in a earthquake area, there are often extra build costs for deeper piles etc that can exceed this too. In Australia I have seen them build the tanks into the facade of the house, to make better use of space.

I wasn't aware of councils charging for wastewater, as isn't that what the rates are for? But probably makes sense in Auckland where you can have a lot of people living in single dwelling or apartments. But basing it off fresh water use isn't great, because many people use water for watering their garden so it never goes into the waste water system.

We would need to consider what the actual goal of mandating something is.

If people purchasing a new home of the plans want a rain water harvesting system, they can simply specify one be included. (say for economic, or self sufficiency reasons) - I know somebody that has a system, primary to avoid staining on toilet's which occurs due to the mineral content in bore sourced drinking water in the area...

If they are a selling point worth the cost developers would likely start including them by default...

In term's of economic's, If $20 of my $47.70 monthly fresh water bill (we are quite high users), could be non potable, and whole setup was $15k worth, payback time (assuming zero maintenance) would be 62 years.... Pretty uneconomic in my book.

In terms of environmental, the impact of individual systems (500 kg odd plastic tank, pumps, extra plumbing etc), would have to be weighted against the impact of a large scale system (incl treatment chemicals).

I don't see any of the above as reasons to mandate, individuals can weigh that stuff up themselves.

One reason that such tech could be mandated is to improve security of supply of the water system, but I don't think this would be the case in Auckland. We have near infinite water (relive to Auckland usage) available in the Waikato river. Only supply issue we have is the amount of infrastructure we have to treat it. In the event that rain water harvesting systems were common, we would still be building to suit a drought return period (say 1 in 100 or 1 in 200 years), so while we would need less throughput capacity, risk profile would be the same.

In locations where clean water resources are scarce, the security of supply equation might work out differently.

In terms of billing for waste water in Auckland, a fixed percentage (78.5%) of fresh water is used to accommodate water that gets drunk, used on garden etc. It's an imperfect system for obvious reasons, but in absence of cost effective, residential scale waste water meters, it is the best proxy for waste water use I can think of. No, it is not included in rates. Waste water services are expensive to provide, and many councils have historic worryingly low levels of investment in this area. Mostly just wanted to get the point across that fresh water is cheap compared to waste water disposal in Auckland.

In terms of the cost's being a small percentage of purchase price, I argue:

We should be comparing to the build cost, and not include the value of land. Build cost the key factor that makes building homes viable, something we need more of in a housing shortage.
A 15k system would be 3% of the build cost of a $500k build... Quite material in my book.
We need a really strong justification before making anything compulsory. I don't think we have it.
Slippery slope argument. If we mandated the following on all new builds, you would stuggle to buy a new home for under $1.5m...:Large $50k solar & battery systems, tripple glazed window's, off street car parks to be the number of bedrooms + offices + 1, EV chargers for every carpark space, heat pumps for every room, 300L heat pump hot water, 4x cat6 networking drops to every room, power outlets on every wall of every room, balanced pressure ventilation system's with hepa filtration, minimum 40m^2 garden, central vacuum system. Sure the dwellings would be super nice, but you have just made lower cost new builds unavailable.

I think the comparison to unavoidable costs like earthquake appropriate construction is a red hearing

Should note that a decent chunk of kiwibuild style new builds in Auckland are extremely space constrained, and many already have stormwater dentition tanks due to high site coverage. For some such developments the need for 10m^3 rain water harvesting storage would make them nonviable, or lessen the density that can be achieved. Clasing with our need for more housing.

As an interesting case study there was in stonefeild's auckland, a third pipe "non potable" water supply was included to all the new houses (early 2000's). In sort, $7m was spend on this system in the name of sustainability. Water care ended up taking the system over (prior to completion) as part of the supercity merge. They crunched the numbers and found it was going to cost 5x to run this system compared to just feeding it with normal treated water.

I have absolutely no issue with people that get rain water harvesting systems for any reason, but think there is a strong argument against mandating something so expensive and large in a city like auckland.

neb

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#2802203 27-Oct-2021 19:16

Scott3:
I don't see any of the above as reasons to mandate, individuals can weigh that stuff up themselves.

They do, the equation is quite simple:

Cost of not putting in a tank: $0

Cost of putting in a tank: Much more than $0.

So it's a very straightforward decision for 99.95% of the population, and doesn't take more than a second to resolve.

We don't need a mandate, what we need is incentivisation like a rates rebate or cheaper water in order to get people to actually think about putting in a tank, and what the advantages could be.

Scott3

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#2802274 27-Oct-2021 21:03

neb: They do, the equation is quite simple: Cost of not putting in a tank: $0 Cost of putting in a tank: Much more than $0. So it's a very straightforward decision for 99.95% of the population, and doesn't take more than a second to resolve.

And I would respect their decision to not have a rain water harvesting system bundled with their house, especially given the poor return on investment.

neb: We don't need a mandate, what we need is incentivisation like a rates rebate or cheaper water in order to get people to actually think about putting in a tank, and what the advantages could be.

Not sure what if any benefit is provided to justify any incentive. Cheaper water would be partially perverse. Discounting customers who are more expensive to serve (there demand spikes at dry times when their rain water tank runs dry and falls over to towns water).

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