Need Help Coming up with a rainwater collection system

A lot of people who go into permaculture are very creative and technically minded. I, unfortunately, am not one of those people.

It’s come to my attention that I really need to install some rainwater collection cisterns on my farm. Our region has a dry season and a wet season, and while I’m hoping that my system will be able to make it from spring to wall without supplemental watering, it’s probably wise to plan on at least some irrigation. My land is flat, which rules out swales for slowing down runoff. I basically have a flat six acre field that I am planting into a food forest. I’m building hugels in it to conserve water, and I’m mulching as much as I reasonably can (which so far is the hugels and in the vicinity of the trees themselves).

What I would like to do is to come up with a system of raised concrete rainwater tanks that could store water collected off of my buildings. I would like to be able to gravity feed from these via hose to my field. I’m thinking about building some sheds out in my field anyway, and was planning on collecting rainwater off of that. I also have a garage and a barn that currently have metal roofs.

Does this seem doable? Does anyone have advice or recommendations? I’m hoping to avoid plastic due to leaching and such.

James Landreth wrote:

What I would like to do is to come up with a system of raised concrete rainwater tanks that could store water collected off of my buildings.

Does this seem doable? Does anyone have advice or recommendations? I’m hoping to avoid plastic due to leaching and such.

Aren't concrete tanks an awfully expensive way to collect/store rainwater?

I've heard of some people, like the Bullock brothers on Orcas Island, use papercrete which might be cheaper. I'm open to materials suggestions, even plastic if it's very inert. I'd just prefer to avoid it if possible

I have written extensively on this site about collection of rainwater. A search for it will answer many questions and deal with naysayers.
Where are you located?
If in North America, there are plenty of tank suppliers, study the installation requirements and purchase the biggest tank you can afford [22.000 litre], because the bigger tanks are better valued for capacity cost and allow time
for the water to settle and keep extra healthy.
Small tanks don't allow enough settlement and oxygenation time, because the water is passing thru too quickly

As John suggested, I'd check with the agricultural dealers/stores in your area about catchment tanks. They come in all sizes and materials. They could also provide installation and maintenance information.

Collecting off of metal roofs is fine. Gutters and pipes to the tank does the trick.

Hi John,
I'm in Washington state in the USA. I've read through some of your material. I'll be sure to try to take another look at it more in depth. A lot of the suppliers around here offer plastic only. I've heard mixed things about leaching and different kinds of plastic.

Thanks, Su Ba. I'll try asking at some of the local feed stores if they know of suppliers.

I am wanting to expand our water catchment also and have been concerned about plastic leaching nasty chemicals.

I've been thinking a lot about this as well for my property and done some pricing.  Old fashioned wooden water tanks surprised me with the cost/longevity advantages.  I've built a lot of large concrete tanks and they almost always require epoxy coating inside or tile, plus there have been cracks.  In the end, I think I will go with something like a shotcrete swimming pool with a cover.  Tank capacity is really something where you can see the benefits of exponential growth.  Double the size, quadruple the capacity kind of thing.  I think 2 good sized tanks would be ideal so you could do maintenance/cleaning on 1 periodically.    

Thanks, Myrth. I'm glad you understand my concern.

Daniel, why shotcrete? Do you think it would have fewer problems with cracking? I hadn't thought about wooden tanks. I wonder if old fashioned wooden water towers would be an option.

James,
Definitely do look into the wooden tanks, I have an HOA(even out in the country) that wouldn't go for one.  All of the shotcrete that I have seen applied had fewer cracks than a traditional poured wall and gunite is probably even better.  Gunite is mixed at the spray tip, whereas shotcrete is mixed before and pumped.  A poured wall can be done right, but you have to have a good mix design for whatever concrete you use.  The biggest advantage to the shotcrete is that you can get nice double curved shapes which do strengthen things.  I am kind of split on a couple options though to tell the truth.

I have done ponds that were large and decorative but only consisted of a simple 4' tall wall on a strip footing.  There was no concrete bottom to these, only a foot of specialized sand on top of a pond liner(for ballast and protection) that ran up the concrete wall.  Yes, the liner was some kind of rubber, but I know that they make some that are safe for drinking.  The advantage to this design is that the depth of water is only 4' and doesn't put as much pressure at the base and we used like $20000 in materials to hold 240,000 gallons of water.  The disadvantage is that it will require more space and doesn't have a cover, which I will need, to prevent evaporation and help keep the water clean and algae free.  The cover might even be used to collect rain.  If you excavated properly, you might even be able to forgo the concrete entirely.  I think I've convinced myself ha!  I would get a smaller tank to hold the potable water after treatment, but for plants and livestock the pond would be good enough.
 

James, check the facts about plastic tanks.
I doubt people who talk about supposed dangers have actually studied the issue.
Here they are made of food grade material, are used extensively and there has not been a record problem with them.
You do not need to drain then yearly to clean them, I have not cleaned tanks in 20 years, but if you want to clean them a syphon system can be built
that cause the inserted 90mm pipes on the floor of the tank to suck the floor clean when ever the tank overflows.
Its a very clever concept. I will look it up if you cannot find the details.

Also if you are talking larger than 20,000L tanks huge ones are built with steel and have a loose plastic liner. I have one 200,000 L
This may be of interest as well
Windmills for pumping water

once youve identifyed what it is that you need (water collection and containment). set about with the meterials and cost. i would start with how much can you afford to spend on this project, whats your budget. plenty of cash makes this easy . go get what you need and build it as big as you like , better still pay someone else to do it for you. but whos got money for that . you wouldnt be here if you could. so im thinking your budget would be as low as it can be. whats the soil like . if you have clay you could build with that and a digger to make something to slow down the water long enough it lasts you though the dry season .
if you want this done fast it would cost more , more time to build this would mean you could do it yourself . say use a shovel , rather then hire a digger. longer , but cheaper.
if i was to have a stab at a design . i would go for one made of plastic and concrete. bigger for the same price of plastic tanks.
dig a whole . layer the sides and bottem with plastic (my first choise would be black bin liners glued over each over to form a barrier. then a layer of concrete over that . cover it in a simple manner(tarps are realy cheap). compact the earth before the plastic would help slow down the leaks later. it would leak after time . but the amount of water you have would be more then enough with leakage.hell sounds like it would be a nice job on summer to jump in and seal up the cracks.
bury the whole thing deep . put a solid roof on and grow veg on top of it.
i know you wanted gravity feed . but i fear gravity fed make it more exspencive if built above ground . below ground , you can use the ground itsself to suport the walls , useing less concrete then if you build about ground as the concrete would need to be thicker or use bricks.
you have wind , use that to pump the water up to a smaller holding tank if you want your gravity fed system.
i cant think of a better meterial. you never know what you can find that others are throwing away that could change this build. but i think this is not perfict salution , it will leak after time. but you will have so much water contained for so cheap a cost , you should spare some water to leaks.
or just get some plastic tanks like what he said above. would be easyer. i realy would ask myself , just how much water do you need.
well good or bad , thats my take on the matter in my half assed manner.

You cannot afford to have any leaks. Even a msall drip will drain a large tank fairly quickly

Thanks for the advice, everyone.

Whatever material I go with I would like it to be gravity fed. I live in a country whose infrastructure is aging; in a lot of places blackouts are becoming more and more frequent, and in my state a lot of our dams have not been maintained properly. Many have cracks, including a local one (Riffe Lake) which was largely drained due to earthquake hazard. Whatever your politics, the United States has not had a government which has been responsible about infrastructure maintenance in a long time. I don’t feel secure relying on grid electricity anymore.

As to solar panels or wind generation:
A friend of mine uses solar panels on her farm, and they’re vital to the maintenance of her aquaponics. Her panels stopped working this year and, with solar technology evolving rapidly, she wasn’t able to find parts compatible and tried to replace them. Because of the trade war it was hard for her to afford to due to the tariffs. I don’t care about the trade war or politics here--my point is simply that relying on electricity, whether home generated or based on the grid, seems to me to be an insecure way of setting up your farm. The trade war could have just as easily been a recession compromising her income and ability to afford solar panels. Both on grid and off grid electricity seem to be reliant on the wider industrial economy, and as that is largely unstable these days, I would prefer to have a gravity fed water system.


Example of the dam hazards that I’m talking about:
http://www.chronline.com/news/earthquake-fears-tacoma-power-plans-prolonged-low-levels-at-riffe/article_b34e4642-f452-11e6-a01f-9bda5b04f57b.html

https://www.nbcnews.com/news/us-news/65-foot-long-crack-washington-dam-repairs-itself-n45606

you say you want gravity fed system , but you live on flat ground all around . if i understand rightly. you have what ever the hight of the catchment is i.e. you roof and the ground where the plants are . thats what you have to play with . in order to store the potential energy in the water , it would need to be stored above ground. as the water levels drops in what ever you choose to contain it in the power to push it around your property drops. so the hight up you store it , the more energy it will have to go horizontal. how far away do you need to get the water from the place you catch in from?
i realy would store it underground and have a smaller tank above ground driven by the wind . you should get a lot of wind if you live in a flat part of the world. you wont need to use all the water at the same time . so the wind could just top the tank off all the time and fill it after its been used.

This green oasis is a drought-proof village in Rajasthan, India