Wednesday, June 17, 2015

Planning for water scarcity

It is winter, the rainwater tanks are about 80% full, and I'm planning for summer. I know that, for our water to last through summer, we need to gather every drop possible, and then conserve it throughout the dry months. It can be dry from November to May some years, and when this is combined with hot weather, lack of water can be difficult. Wikipedia puts it well: "Nine of Adelaide's ten warmest years ever recorded have occurred in the last decade: from 2002 to 2014. Summer 2013-14 was the hottest summer on record, with a record number of 13 days exceeding 40 °C (104 °F), while Autumn 2014 was the warmest autumn ever recorded in Adelaide's history.[48 The following summer, in January 2015, bushfires burned out of control after days of extreme heat conditions in Sampson Flat, South Australia which then spread towards the outer northern suburbs of Adelaide, toward Greenwith and Golden Grove.[49] The heatwave and fires caused widespread destruction, health problems and fatalities. The number of heat-related deaths in Adelaide is expected to more than double by 2030."
In other words, summers are hot and dry, they are getting hotter and drier, and this trend will continue.

I've written other articles about our water collection and storage:
Rainwater modelling (assess sufficiency of storage against historical meteorological data for Adelaide)
Water at my house: rainwater
Progress report on water systems

Grey water

Last summer I caught our washing machine water in a wheelie bin and bucketed it onto the garden to reduce the watering load. That's a lot of work, and I don't think it's sustainable (for my body!) -- I get plenty of exercise, and don't need more. I wanted to set up a greywater system to save me work.

There are some good online resources about greywater systems:
Art Ludwig has fabulous diy info for greywater on his website. I spent quite a bit of time reading his site, and have understood that:
  • pumps are to be avoided
  • use gravity to get the water where it's wanted
  • keep the system simple
The basic principle is that the washing machine puts the water into a white bucket, from which it drains through a black pipe, to our front yard. That pipe finished underground (about 200 mm  deep) within an upside-down plastic plant pot with holes drilled in the sides. That water then falls on the ground there, and the whole thing is covered in mulch.

The bucket. The washing machine outlet is visible behind (grey corrogated pipe), and the exiting black pipe goes to the front yard. This bucket exists to protect the washing machine pump -- if it was connected directly to the black pipe and there was a blockage, it could burn out the pump. The white bucket has an overflow hole on the other side (below the grey water inlet). If the water is not draining, it will exit through that hole (to protect the pump)

The side of the house, showing the pipe. I have tried to make the pipe gently slope down right along the length of the house so that there are no "local minima" in the pipe (places for crud to accumulate and block the pipe). You can also see a heap of broken concrete. This is concrete that I've dug up elsewhere, but I don't want to put it in landfill, so am looking for another use for it -- maybe shoved down the sides of a hole to hold in a post...

Here's where it terminates in the front yard. I've put the bamboo on top, because I don't want someone walking on it and breaking it.
The idea is that there is a large mulch pit where the pipe terminates, so that the grey water can diffuse through the mulch and generally wet the area. Plants will get their roots into the mulch, but because the water falls from the pipe and there is an air gap, plants won't get their roots into the pipe and block it. (fingers crossed).
Instead of digging a circular bed, I've dug a spade-width trench over to a couple of other trees. I've filled this trench with mulch. Probably the trench is currently too small to accept all the grey water, so I'll need to dig some more -- other trees can then access the water which will be good. I've got two citrus and a white sapote near here, so the water will be appreciated.

I've used 1 inch pipe, which is narrower than recommended (from memory, Art Ludwig recommended 40 mm pipe), so I expect it will get blocked from time to time. My plan is to put the hose in at the white-bucket end, and just blast it through. I hope it works!

Salt build-up

This is always a concern with grey water. Adelaide town water is very salty, so we're ahead here (because we run on rainwater), but we use low-salt soap in the washing machine, and we use it very sparingly.

The front garden

I thought I'd include a few photos of the front garden. We've been here about 18 months and the entire garden was couch grass when we moved in. All the grass is now gone, and there is an average of 150 mm of mulch across the yard with about 12 trees planted.

Mandarin -- this tree has been in the ground for ~21 months, and seems very happy

Almond tree -- this tree has grown amazingly (~21 months in the ground) -- we even had some almonds in April! You can also see the rainwater tank (top left). We had a few discussions about whether it was aesthetically ok to put a rainwater tank in the front yard. I've wrapped wire around the tank and we're growing a passionfruit vine up it. I see us as trailblazing a new garden aesthetic! ;-)

Orange tree -- has a few oranges on it (also in the ground for ~21 months)
I was a bit hesitant as to whether I should let the citrus trees fruit, but I decided to just let them. I guess it's possible they won't fruit next year (because of the stress). Time will tell...

There's lots more work to do here. I want to plant at least another 6 trees this winter. I'm thinking another lemon, and some more nut trees, an avocado (our last one died). Any other suggestions? Out the back we've got apples, pears, nectarines, peaches, plums, walnut, fig...


  1. Hi Angus,
    Top work! I'll drop a longer comment over the next two days, but wanted to say how good the place is looking and also keeping the systems simple is the best way to ensure they stay working and pumps and sludge don't really mix well- I spotted a recent article about handiwipes of some sort which is bringing the New York sewer system to its knees. Your almond tree is growing faster than the ones here - they like a drink over summer. And, just out of interest, why is the northern-ish (?) house wall rendered, but not the other side? Oh yeah, the mulch is an exceptionally good idea to reduce the salt and build the soil at the same time. Very excellent work. Cheers. Chris

  2. Hi Chris, thanks. Yeah, the almond and apricot have gone (um) bananas ;-) They're clearly both very happy and it's nice when that happens. We've got a peach out the back that is the same -- it has gone from a foot-long stick to a 2m tree in 24 months.
    The trees I showed you are in our front yard, which is South-facing. The Southern, Eastern and Western walls of the house are rendered. At the back (Northern side) is a lean-to, and that is bare brick. It works quite well, because the Northern wall gets winter sun, but the Eastern and Western walls keep cooler in summer. We haven't changed this at all -- I think the rendering might be original.
    I didn't know mulch helped reduce salt in the soil -- is that effectively by dilution?
    The washing machine seems to be draining fine so far, so hopefully it stays happy :-)

    Cheers, Angus

  3. Hi Angus. Very amusing! You could probably just about do bananas in your part of the world if they were really sheltered from the winds. I've seen them growing in Melbourne. Fresh peaches off the tree are a true summer delight. I've got an Anzac peach here that hasn't gone deciduous yet.
    Thanks for the correction about the wall orientation. Perhaps it is dilution and that would certainly be a factor, but all I've read is that healthy soil, with lots of soil life and plant roots seems to be an effective counter balance to the salt - you also want to reduce the evaporation as that process leaves the crystals behind. If there is a build up of salt that you are worried about, you will certainly be able to see the crystals.
    I'm sure it will stay happy and be grateful for the extra water over summer.
    I forgot to ask whether your wife enjoyed the PDC?
    PS: I enjoyed the overshoot blog too.


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