Wednesday, 27 April 2022

Considering water use

In New Zealand, most councils have moved to a water metering system, using loggers on the mains supply where it enters the property. There is a certain amount of use which is considered the 'base line', then households are billed for what is used above that.

Our household water use has always been quite low. We have always planted low maintenance gardens because, basically, we can't be bothered faffing about watering plants. We plant natives, and they grow by themselves. The main consumer of water was always our vegetable garden, our washing machine, and our dishwasher. 

So when we built our own house way on a 10Ha block out in the country, one of the many things we considered was water. How we would get it, how we would store it, and how we would ensure that we had enough. We had long ago shifted to a front loader washing machine (because it used 66% less water than a top loader). I bought a Swedish dishwasher (washing up machine) that used less water than I would if I washed the dishes in the sink... and got them cleaner! That left us with pretty much only the vegetable garden as our largest water user, but as it fed us, it was a necessary use of water. The toilet moved up the list as a significant water consumer, so I bought dual flush toilets, and put a brick in each cistern to artificially reduce the water volume. Sorted.

In our planning process, we worked out how much roof space we had to collect rainwater, and how much tank volume we would need to store it. Then we could be sure that we could reasonably stay off a mains supply scheme. With 200 square metres of roof (sheds and house) and an average rainfall of .75m/annum, we put in 71,000 litres of storage tank capacity. We knew we had rain enough to fill the tank volume roughly four times each year. 

The trickiest part was working out how much water we used annually. We knew we did not use more than the base-line rating level, because we didn't get water bills in the city. In the end, we decided to suck it and see. Well, in 11 years, we only ran out of water once (when the builders were building the house, and emptied the tanks by accident). I now know that we use between 1,000 and 2,000 litres of water a week, INCLUDING our garden. That average weekly use works out to about 78,000 litres/annum. Our tanks are always full.

Now, we are not hairy-toed stinkies who never wash. While we mostly shower (and have a water-conserving shower head), I love running a bath in winter and having a lovely soak. I just don't do it all the time. We know that water is a valuable resource, and - as we have to collect it and look after it - we need to ensure that we have enough for any time of scarcity.

Recently I was watching a DW documentary (2021), looking at water use in Las Vegas. They examined how the city was conserving water, with household use having fallen by a third. It all sounded great until I realised that in 2018, Las Vegan (!) households used an average of 100,920 gallons (Mullenix, 2020); an appallingly high 382,023 litres/annum. And that was with a 33% reduction! I was gobsmacked. I still am.

We use 78,000 litres of water per year, and Las Vegans use five times more water per year than we do (and their consumption used to be almost six and a half times ours!). I am still staggered that this was considered to be 'good'. 

So I looked at what New Zealanders use on average. While not so ghastly as in Las Vegas, it is still high at 236,520 litres/year (2.7 people x 240L/day; Catley,  2017; Greater Wellington, 2011).

No wonder water is considered to be in short supply with use like that.


Sam

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