Make My Garden Grow ... in a drought year!

February 8, 2009 8:25 PM

Rainwater collection, on the cheap, in a rental?

I live in a rental house without gutters. I would love to collect rainwater this summer (what little rainwater is expected) to water my garden, but I can't put up permanent structures nor can I attach anything to the house.

Given that we've had pretty much no rain so far this year, I'm guessing that we'll be on watering restrictions in summertime. Anyone with a big bushy produce-forest in the backyard will be suspect and subject to being ticketed. I'm already planning to conserve gray-water wherever possible, and I've planted drought resistant plants, but I still would like to gain some fruits for all my labor. That means I'll need more water than I may able to reasonably supply from the usual sources.

Has anyone seen any good ideas for portable, collapsible rainwater collection? Bonus points if I can make them for free or cheap; double bonus points for ideas that don't require a huge cash outlay.

posted by SpecialK to home & garden (15 answers total)

Why not use 33 gallon trash cans? They are definitely not permanent structures.
posted by The Light Fantastic at 8:42 PM on February 8, 2009

Tarp that drains into a trashcan.
posted by fshgrl at 8:50 PM on February 8, 2009

A 55 gallon plastic food-grade drum wouldn't be permanent, plus you can find them used for about $20. Not sure how you will be able to collect the runoff from your roof if there is no gutter, though. Does it tend to pour off of one section, more or less? You need a way to direct it to the collector, either with some pipe or maybe a tarp if the runoff is more spread out. Got any photos of the house exterior?
posted by orme at 8:55 PM on February 8, 2009

I would need to somehow set up a tarp in the yard on a frame, or some other sort of collection system. That's my main hurdle.

There really aren't any roof valleys I can use (think bungalow structure) and I can't attach anything to the house, so no eyehooks or anything to hang a tarp from.

The other challenge is that we tend to get very strong wind gusts when it does rain; I'd need to be able to weight the tarp down and/or the frame would need to be *very* sturdy and able to be anchored securely to the ground, which is conflicting with my desire to be able to furl and unfurl it quickly. I'm hoping that someone's got a great design that's already engineered around these issues that's designed to be deployed in a underdeveloped country or in an emergency situation.
posted by SpecialK at 9:38 PM on February 8, 2009

Can you create a channel on the ground under the eaves to catch the runoff? if so then a cistern down grade could be fashioned by burying a 55 gal Drum horizontally.
posted by hortense at 10:04 PM on February 8, 2009

What about the gutter system? Is it aluminum or something magnets will stick to? If it's magnet friendly, you could use neodymium magnets to anchor a small tarp to it without damaging it... neodymium permanent magnets can be extremely strong. Here's a place selling them built into hooks, which might work well for you. Two or three of the $8 variety should be more than enough holding power to hang a 4x6 tarp from, and this meets your "break down in a hurry" criteria as well since all you'd need to do is unhook the tarp and roll it up.
posted by barc0001 at 10:28 PM on February 8, 2009

Two thought:

1. You can buy long thin tarps and set them up about 1-2 feet above the ground where they will catch the rain coming off the roof and funnel it into a bucket. You'll have to drive some stakes into the ground but taking advantage of the roof's surface area is the only way you're going to get a significant amount of water. Leave the stakes in between rainstorms and set-up with some paracord should take 10-15 minutes.

2. Trees actually evolved to direct rain water down from their branches to their trunks. If you place a skirt around the bottom of one you can take advantage of their surface area. However, you'll be stealing water from the tree and if it's really dry you may kill it.
posted by 517 at 10:32 PM on February 8, 2009

How much rain do you get in the spring and summer? You're going to need to collect the equivalent of approximately 60-90 gallons per dry week for the average water uses of a 10x10' garden. (Rule of thumb is an inch to an inch and a half of water needed per week*; one inch of rainfall is .62 gallons per square foot). So if you get a storm that drops 2-3 inches twice a month, you'll need a 10x10' collecting surface and storage space for 60-90 gallons for a 10x10' garden. Less frequent rain= larger storage capacity. Less rainfall per storm= larger collection area.

* extremely variable depending on plants, weather, soil, delivery system.
posted by oneirodynia at 10:48 PM on February 8, 2009

less frequent rain= greater need for storage capacity. Less rainfall per storm= greater need for a larger collection area. Sorry to be unclear.
posted by oneirodynia at 10:52 PM on February 8, 2009

Barc: There is no gutter system at all... otherwise I'd just tie in to downspouts.

Also, no trees.

oneirodynia: Ooh, thanks, that gives me some interesting information that I didn't have before about what the need actually is. Our average annual rainfall is 39 inches. So far this year, we've had less than .25 of an inch. My garden is 8' by 8' and 20" deep. Thanks for the numbers!
posted by SpecialK at 10:59 PM on February 8, 2009

What if you got something like this pop-up tent for your yard and modified it so that the point was inverted like a giant funnel. Cut a hole in the point and weight it so that the water could run into a barrel underneath. I think it could be put up pretty quickly and staked into the ground, then fold up and stored afterwards.
posted by lunaazul at 11:00 PM on February 8, 2009

oops, folded up
posted by lunaazul at 11:03 PM on February 8, 2009

Oh, and if you could place it so that one edge is underneath the roof line, that would be even better.
posted by lunaazul at 11:07 PM on February 8, 2009

Whatever you do, definitely make use of the roof as a part of the system, because this is the only way you can make your collector small, which in turn is probably the best way to make it cheap and quick to set up and take down. If storms predictably come in from a particular direction, put the collector on that side of the house.

You need about 40 gallons a week for a garden of that size, maybe more when extreme heat increases the rate of evaporation.

If the soil there is sandy and drains quickly, you should incorporate as much water-holding organic material as possible into the garden soil. It looks as if July is your driest month, during which you'd need to roughly double the amount of water the garden gets directly from rain. Depending on how often it rains, you might need a couple of 55-gallon drums for storage. I'd set the drums directly under the edge of the roof and build some sort of funnel arrangement directly over them to minimize the space taken up by the apparatus, and to avoid the need to pump water up from a ground-level collector.

Also, I'd ask the city whether the watering restrictions might allow the use of drip irrigation.
posted by jon1270 at 5:07 AM on February 9, 2009

Build something next to the house. Get a couple pieces of the V shaped material used to seal the roof ridge of steel sided barns and the like and make a couple sets of legs, place that under your eaves like a gutter and have those drain off into your rain barrel.
posted by Kid Charlemagne at 5:30 AM on February 9, 2009