Our water supply on the quinta comes from a stream that runs through it, plus a couple of small springs. When we first moved onto the land we collected buckets from the waterfall, then graduated to hose-piping our water direct from the stream for household use and irrigation.
But 2012 changed all that. We had a very dry summer following 2 years of failure of the winter rains. After diminishing to a mere trickle in February, the water in the stream stopped altogether in late August (the village above us used it all), only starting again when the rains did. I installed a 1,000-litre plastic drinking water tank for our household needs, fed mostly by spring water, leaving the stream for limited irrigation. The vegetable garden coped surprisingly well thanks to a lot of mulch, but we lost all our water-hungry plants like squashes. It really focused my attention on how vulnerable we are to drought. Since then I’ve been planning to build in as much water storage as practicable, and collect water both from the stream and from roof rainwater catchment.
This summer, along with all the other projects under way, we’ve been putting in some water tanks. Work has been progressing on a small rainwater catchment system for the smaller of the two buildings here, and also on two much larger tanks which will form the main hubs of our water distribution network, supporting both domestic use and irrigation.
My thinking on the subject of water and its storage has been enormously influenced by the work of Viktor Schauberger. Schauberger’s insights about water are profound and far reaching. He observed that when water is exposed to light and warmed by the sun, it loses its vitality and becomes sluggish. Exposed for long enough, it dies. He meant this quite literally – in his view water is a living thing, the lifeblood of the planet, rather than just a simple inorganic compound of hydrogen and oxygen. It’s at its most vigorous and vital when close to its maximum density, ie. at 4°C, and in darkness. It needs freedom to move, to flow, to meander, to be in the way that it is, not forced into straight lines or contained by straight walls at right angles to each other. Straight lines and angles prevent the formation of the natural vortices and circulation patterns that are essential to maintaining water in its optimum state of aeration. Consequently it stagnates, and like anything else that’s died, decomposes and becomes a breeding ground for bacteria, moulds and algae, requiring filtration and chemical treatment to make it ‘drinkable’ again.
The optimum shape of container for water storage is, according to Schauberger, an egg shape. We could do this in ferrocement, but it was going to comfortably exceed our limited budget, so we’ve got as close as we can by using stacked pre-cast concrete rings to form these two tanks, curving and shaping the bottom of the tank to remove the right angle between the walls and the base. Schauberger would doubtless not approve of using concrete, but it was the only economically viable material I could consider for tanks of this size.
The first to be built, on the eastern side of the quinta, will hold around 6,000 litres when it’s finished and supply the smaller building (the ‘wee house’) plus the irrigation tanks and terraces below. Up until now, there’s been no water supply this side of the quinta at all.
The 6,000-litre tank is fed from a main tank of roughly double that capacity built into the remains of what was once the uppermost holding tank for irrigation water right next to the stream. The pipeline between these two tanks will also supply the 1,000-litre tank for the cob bathroom, currently on a hosepipe feed direct from the stream. The main tank will also feed the larger building on the west side of the quinta.
This is how we built them …
Although these tanks look enormous, the amount of water they hold is not a lot when considered in the context of irrigation requirements for a well-cultivated quinta. Together with our rainwater catchment capacity, both installed and planned, we’ll probably be storing no more than 30,000 litres in total (last year’s plans for a 33,000-litre ferrocement rainwater harvesting system have had to be changed due to budget constraints). The ponds, once completed, will keep another 10,000 litres or so on the quinta. But storing an entire summer’s irrigation requirements isn’t the intention. Once full, the tank system will be topped up daily for as long as the stream runs and if it does stop again in late August/early September, then we will hopefully have enough capacity to keep the vegetable garden on minimum maintenance watering until the winter rains come in.
Regardless, it will certainly be an improvement on what we had before.
Joao Miranda October 17, 2013
It looks like a great idea for a limited budget like in my case.
How much did you sent on it overall, i.e., including materials, specialized work (if any), etc ?
Also thanks for posting the pictures!
Quinta do Vale October 17, 2013
They’re probably the cheapest solution for the sort of volumes they contain, but they’re still not cheap. I can’t give you the answer to your question because the work isn’t finished yet. Also the volume of concrete required for the base will depend on your situation and how deep you need to dig to create a strong enough foundation to take the weight. The concrete rings themselves vary in price according to diameter. The 2m ones, for example, are €85 each (0.5m height) + IVA from our local supplier. You’d need to factor in the hire of a JCB and driver to offload the rings and lift them into place. The cement jacket that’s poured to surround the rings creates a few problems here in Portugal. In the UK, you can hire formwork specially for this, but we haven’t been able to find any here and had to improvise our own. The corrugated roofing sheets we used weren’t ideal, so we’ve ended up with an interesting shape to the first tank and the use of a lot more cement than was necessary :-)
Frank Antonson September 29, 2014
Your work amazes me!
But it looks expensive — not for what it actually is, but for an “average Joe”.
Whay aren’t there more comments about your projects? They are amazing.
Quinta do Vale September 29, 2014
I guess it depends on how you define ‘expensive’ and ‘average Joe’. And it also depends where in the world you live. As a general ballpark, 85% of the cost of any build is labour, so if you can afford the 15% material cost and have a few resourceful friends who are handy with stuff to help you out, then it doesn’t have to be particularly expensive. A lot of what we do here is with materials we source on-site or recycle from local dumps and scrap yards. I was lucky enough to have a small legacy to be able to pay some friends to help me out with this, but equally well we trade labour for labour on each other’s projects in times when there isn’t so much money to go around.
Prajna September 12, 2015
Hi Wendy, another option rather than a concrete jacket for the cylinders might be an Italian flexible cement based waterproofing compound called aquafix. It costs about €60 for enough to coat a 10,000 litre tank. You paint it on to smooth cement. I’m not sure how ecological it is but I have been told it is safe to use on drinking water tanks.
Quinta do Vale September 12, 2015
Hi Prajna. Yes some nearby friends used this, or something similar, on the inside of their concrete ring water tank (which they built after seeing these ones) rather than go through what we did with the concrete jackets. When I spoke to them about it last they weren’t yet ready to be 100% confident in it because the tank wasn’t long completed and there’d been one or two issues, but as far as I know it’s working fine.
It would certainly be a lot cheaper and far less hassle than a concrete jacket. Any ideas how long it’s supposed to last before needing another coat? And how smooth does the cement surface have to be? – ie. would you need to put a skim coat on the typical surface of a pre-cast concrete ring?