The Issue of Rain Water Catchment

Hardly a week goes by without someone suggesting that I set up some rain barrels and capture some rain water. I had a similar notion when I first got the land last year, but I’ve since discarded it as being mostly unfeasible. But, since it keeps coming up, I figured I’d write a post describing why it’s probably not worth the trouble, at least for now.

At first glance, capturing rain water seems like a simple and obvious idea, given my lack of any other local water source. The area I’m in gets over 30 inches of precipitation a year, mostly between the months of October and April. During the warmer months, though, it’s generally very dry. This year has been a bit of an exception, with two very heavy days of rain so far already, but the average precipitation for the whole month of August is less than a third of an inch (although, I suspect the median rainfall for the month is more like zero, with exceptions every few years bringing up the mean).

So, what’s wrong with rain water catchment? The main problem is that most of the precipitation comes down during the colder months, and when I say colder months, I mean freezing months. Last year, lows in November were already falling to the low 20s F, and during the winter months, single digit lows are a regular occurrence. Last winter, it apparently got cold enough that a bottle of soda I’d left in the utility trailer had exploded, and some of my 2.5 gallon water containers had also been damaged. So, freezing weather creates, as far as I can foresee, two problems.

The first problem is that whatever container I collect water in has to be able to withstand freezing. The rain catcher I ended up using for my water tower specifically says that it needs to be emptied before frost. Other rain barrels and water tanks might be sturdier, but even if the container can contain freezing water without bursting, there’s still the fact that big chunks of ice could be difficult to work with if I wanted to use that water during the winter. One possible solution would be bury the water containers below the frostline, but that really complicates what should be a simple solution.

The second problem is that much of the precipitation comes down as snow. While rain can be captured off of my hut roof fairly easily, snow might be trickier since it obviously doesn’t flow the way water does. It’ll first accumulate on my roof, compact, maybe even freeze into ice, then eventually slide off in big heavy clumps. These clumps could come off the roof with sufficient force to either tear off the gutters, or fly right over them. I could create a surface with a nice gentle grade where snow can accumulate and stay without falling off as it gradually melts, but that still leaves the aforementioned issue of the water having to be stored somewhere where it won’t freeze.

These problems (and possible solutions) are further complicated by the amount of water I’d need to make the whole solution worthwhile. This summer, my garden used at least 25 gallons of water a week, and I used another 10 or so for drinking and bathing, for a total of about 35 gallons a week. If we say the dry season lasts 6 months (which is being generous), that’s 26 weeks X 35 gallons = 910 gallons. And trying to bury a 1000 gallon tank, even partially, is no easy task. Besides, a tank of that capacity isn’t exactly cheap; rule of thumb is roughly $1 per gallon for a good tank. On top of that, if I need to build a separate water catchment surface other than my roof, I’d need a surface over 80 square ft in area assuming I manage to capture 20 inches of precipitation, which is probably optimistic (the math: 20 inches ~= 50.8cm, which means 5.08 liters per 100 square cm, or 508 liters per square meter, so to get 1000 gallons or 3785 liters, I’d need 3785/508 ~= 7.45 square meters ~= 80 square feet). And that’s just to barely cover my current needs, which are pretty minimal. I guess I don’t have to try and cover all my needs this way, but seeing how little work it currently is for me to haul water from town, I’d want a replacement to be significantly less work to justify the up-front cost.

Of course, compared to digging a well, which could cost me over $10k, a 1000+ gallon water catchment solution could still be cheaper. So I wouldn’t dismiss the idea entirely, but nonetheless, I don’t think it’s quite as simple as most people seem to think it is. Or maybe I’m over-thinking this. Has anyone successfully setup water catchers in similar climates?

19 thoughts on “The Issue of Rain Water Catchment

  1. With just 1/4-inch of rain, we are able to capture 220 gallons of water, and possibly more, but that is all of the storage capacity we currently have.

    How deep is your water table there? Hand digging a well isn’t that hard to do if you have the time to do it. Of course, if the water table is more than 25 or 30 feet deep, then I wouldn’t recommend it.

    • That’s pretty impressive. What kind of climate are you in? I don’t have good data on the water table, but the nearest well that I know of is a mile or two away, and I heard theirs is 150 ft deep.

      • I wouldn’t rule out hand digging/drilling a well just because a neighbor has a deep one. From my understanding, well companies like to drill at least 100′ deep to lessen the chance of an aquifier running dry, or becoming polluted from surface runoff. I (in Michigan) have had neighbors 1/4 mile away hire a company to drill a well and they went down over 300′. My well is just over 20′, and another neighbor who did it himself is only at 17′.

        • I’ve heard from someone who digs wells that you want to be careful with anything above 50′ because it could be contaminated by surface run-off. Is that something you’ve had to worry about? Or do you just filter/sanitize the water you get?

      • I have been living here for two years, and had it tested before I moved in. I drink it right from the tap without filtering and have not had any problem with the water. I prefer it to city water. The area is fairly rural so there is no industrial pollution, and we do have sewer so I don’t have to worry about septic tank seepage.

  2. Yeah, we encountered similar questions – and I still dabble in thinking about them. But the fact of the matter is – with the well I do have a rainwater catchment, but it is an aquifer I don’t have to fuss with. During the winter, we have more water than we could ever use and during the summer – well, it would be hard to store any meaningful amount of water. Drinking maybe – but watering crops isn’t going to happen, even feeding animals might be a stretch. Consider the well – there’s more than one way to skin a cat there, you can try putting in the well yourself by hammering sections of steel pipe with a bore bit at the tip. Once you get the well installed, a solar or wind powered pump will allow you to have so much water that you could profitably build a cistern and store as much as you’d like with overflow any point in the year. Rainwater seems nice, and I’ve seen some people do it, but it just doesn’t seem sustainable for me, not when wells are a viable option.

  3. I just skimmed your article so forgive me if I miss somthing you’ve allready said. BUT we have rain barrels in the Mtns of Washington State. They have weathered 3 winters and freeze every year without damage. They are the white potable 55 gallon barrels. I turn off the valve and disconnect the hose for winter and the top of the barrel has a 8″ hole in it for the gutter. I believe they are fine because as the water freezes and expands it can go up and out the top if it needs to.

    And even if they do crazy or one does they only cost $20. They are great 3 seasons of the year. Don’t over think it.

      • thats your needs for the entire year? you wouldnt ever need that in one place at one time. besides, you could get like five barrels for a hundred dollars and see how you go. five is more than zero, it’s a start.

  4. meant to type : And even if they do FREEZE or one does they only cost $20. They are great 3 seasons of the year. Don’t over think it.

  5. http://www.youtube.com/user/london1817#p/search/2/Hwy8qdpPY6Y

    I subscribed to this guys youtube feed. He has some interesting videos that really spark my creative side.

    I also read someplace where a guy set up a simple structure like a carport type of a thing, just a roof with supports. I’m sure you could think of something that needs a cover anyway, right? He built it with a slight incline and added a gutter and water catchment barrels to it. His were simple gravity feed, but no reason you couldn’t so a pump of some sort. He had several constructed at different strategic locations around his farmstead. Some near the animal pens, some nearer gardens, etc…

    I’m not sure how practical this would be, and I’m not very familiar with how they are built or how they work, but when I was a kid we had a cistern. It was underground near the back of the house and all the rainwater was funneled into it.

    It was cement, best I remember, and the water filtered into it through different layers of things: graded rock, and eventually a layer off charcoal. It eventually fed into the well. I wish I knew how it was all set up. I don’t remember. It just wasn’t important to me at the time. We used it as long as we lived there and as far as I know it never gave us any trouble.

  6. Sorry to post again… I found this picture, and I think it’s similar to the cistern we had, only ours wasn’t quite so ‘fancy’. I think on ours the rain went directly into the cistern (which is what they are calling a filter in this diagram) and then into a well (or a tank, if that’s what you opt to do). Thought it might help.

  7. Since you have lots of space and an incline, you could use the terrain to collect and funnel down rain and snow. There’s a little lake near where I’m building my cabin (in the mountains around L.A.) that’s fed by melting snow from the hills. The climate is pretty simple: 2-4 days of rain in nov-dec, maybe 2″ to 4″, followed by snow in dec-jan which stays until may then melts, and there’s basically no rain for half of the year and the rocky ground doesn’t retain water. None the less, the water trickles down and forms a little lake that lasts all summer (gets to about 95f) and only dries up a month or so before the rains.

    I think if you used the terrain to your advantage, you could easily collect water as it flows downhill and into some sort of container and use it for the garden with minimal filtering. If it’s below ground, you could actually just make a cistern with concrete blocks, some clay or cement to seal the gaps and some non toxic paint to retain the water. Cheap, but not necessarily easy. Still, in your case, water = growing food, and having it there means you don’t have to drive every time.

    • I was thinking something similar. Use the watershed of your whole property (or a large exapanse, anyway) and filter toward a simple pond. use garden-pond liner on your dame (which could simply be earthern, covered by liner, and probably rocks over that). pond liner “in front” of dam will reduce loss through seepage.

      Start small to try it out. If it works in theory, it’s worth scaling up next year.

  8. One thing I think you are having a problem with is committing to a single source of water, and the difficulty therein. Don’t plan on rainwater as your *single* source of water or you will be in serious trouble, both in terms of the costs necessary for everything needed, but also when you hit a bad month or so and you are in trouble. Instead, look at rainwater as *one* of your water sources. Figure out the optimal balance of cost of equipment, storage, and returns in water. If you can get a small system up for only $100 or so, and it can give you 20% of your total water, you are probably good. Maybe it gives you more in certain months, but that’s fine. If you know in the winter you need 1/4 of the trips to fetch water, in the snow that’s fine.

    Don’t depend on a single source, and work with the dynamics of what’s around you.

  9. Interesting. I was searching for a cheap rainwater collection surface to use for a snow-capable collection system partly spurred by this post.

    I searched “rainwater catchment surface non toxic”, and here was this page in the search results on the first page, which I had already seen and read and incidentally has nothing to do with what I searched. You haven’t been pulling and strings lately to up the ole’ pagerank, hm? kidding, kidding.

    Anyway you can see the approach I’m taking on my blog soon when I post it.

    But you make it sound a lot harder than it is even so. Especially when you compare it with actually hauling in >900 gallons of water!

    You can insulate the tank, and with a few sq meter solar heater like the one on my blog (“4kWh per sq meter of thermal energy on a sunny day.

    Also, btw, I made a typo on one of my previous comments here, when I mentioned the efficiency of AC, it’s the reverse, with AC being higher loss. But I read your reply and yes I agree it’s sort of a wash either way of you are 100 ft away.

    Aslo, while I am writing, you might want to check with some trig and a spreadsheet and solar position calculations to see how much extra electricity you can get from you solar panels with a reflector on the ground below it, and maybe another at the appropriate angle above. I think it would be substantial.

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