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How much rainfall?  RSS feed

 
Tom Connolly
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I am looking at a piece of land - high plains desert - that gets about 8 inches of rainfall a year. I want to put a small house on it that will usually have no more than 3 people living in it. Is it feasible to design a rainwater catchment system for this property for under $2,500? The rain falls on 91 days per year, mostly between October and March. Wells are hit and miss in this area. I have better than basic carpentry skills and am willing to learn more skills in order to save money.
 
Dale Hodgins
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Location: Victoria British Columbia-Canada
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How much acreage and are there any steep areas? Are there laws which would prevent you from trapping water?

The cheapest structure for water catchment is sloped rock. I would choose a site that is 80% rock over a flat piece of very dry soil. The flat surface would have to rely on man made structures for water catchment.

Acute water shortage should make land very cheap. Shortages of land near cities can drive prices far beyond what could be harvested from the land over several decades. A few years ago, I looked at some dry land in the interior of BC. A speculative market had driven the price of one parcel to the point where we calculated the payback from grazing cattle at 800 years. It was dry scrub. Other parts of the country had land with trees, rivers and houses selling for less.
 
John Wolfram
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Location: Lafayette, Indiana
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Typical water usage is 80-100 gallons per day, but let's assume that you use half as much water as the average person (50 gallons a day for easy math). If you are planning on irrigating a garden for your house, you may want to up that number to the full 80-100 gallons. Assuming no rain February through November, you would need 45,000 gallons stored up as winter is beginning to end, that's a pretty big/expensive tank. You'll also need more than 12,000 square feet of water collection surface. Overall, I would guess that unless some of the infrastructure is already in place it will be very difficult to put in an adequate system for less than $2,500.
 
Tom Connolly
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Thanks! The numbers are very useful. I will have a choice of lots...some are sloped, some are not....and then again, I may just pass this up. It would not be my primary dwelling.
 
Brett Andrzejewski
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Hello Tom,

I have some Permaculture friends living in a mountain high desert environment. They average about 10" rain a year. They have several 3000 gallon water tanks. They even built an additional structure, roof with supports and two walls at the moment, just to capture additional rain. I would say that most of their designs plans are around water and are willing to pay extra to have the tanks. They are extremely frugal with water use and average 5 to 7 gallons of water a day. They live off-grid and don't have utility connections.

They have a metered showers
All grey water is recycled/reused
They try not to use water for cooking, mostly solar ovens
clothes washing is by hand
composting toilets

In a really bad drought year they will have purchase water and have it trucked in.
 
Tom Connolly
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So it seems that the more extreme the environment you live in, the more WE have to adapt to the land.
 
Jennifer Wadsworth
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Location: Phoenix, AZ (9b)
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Hi Tom:

Those of us with little water do plan EVERYTHING around it. You might play around with water harvesting guru, Brad Lancaster's water budget calculator. When I teach my PDC - I spend 10-12 hours on water, including teaching water budget and how to get the most use out of the water you've collected.

If you're up for a challenge, it sounds like a great spot. If not, look for land elsewhere. It can be done, but it will take longer to "green" than other places that don't have similar challenges.

Brad's site has lot's of great advice on it so poke around a bit.
 
John Polk
steward
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Location: Currently in Lake Stevens, WA. Home in Spokane
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A very handy number to remember is 1.6

Divide the square footage of roof/catchment area by 1.6, and the results will be the gallons collected for each inch of rain.

A 1,600 sq. ft. house will collect 1,000 gallons for each inch of rain.
A 160 sq. ft. chicken coop will collect 100 gallons from that same inch of rain.

 
Tom Connolly
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John Polk wrote:A very handy number to remember is 1.6

Divide the square footage of roof/catchment area by 1.6, and the results will be the gallons collected for each inch of rain.

A 1,600 sq. ft. house will collect 1,000 gallons for each inch of rain.
A 160 sq. ft. chicken coop will collect 100 gallons from that same inch of rain.


That is a helpful number. So a 1,600 square foot home is going to collect 16,000 gallons of water with 10" of rain a year, or almost a third of the suggested needs for a year. I was looking at closer to a thousand square feet, but also have plans for a greenhouse, garage and a small utility building/barn. A large water tank (sounds like I would need one) would be a useful catchment source, so I will likely have 3,000 sq. ft of roof to work with. I am fine with using compost toilets, reclaiming greywater (I have not yet built the house so intend to plumb it accordingly). Probably a good place to start is to map out what I would like to do with the land, project that into water requirements and then go from there. I would also need to develop a rather disciplined mindset about life before I seriously entertain this idea.
 
John Polk
steward
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Location: Currently in Lake Stevens, WA. Home in Spokane
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With that little rainfall, rain gutters on any possible collection area are in order.

(Hint: you might save a ton of money if you shop at Habitat for Humanity for used rain gutter parts.)

I keep hearing people complain about having to carry buckets of water out to the chicken coop every day.
Rain gutters and a barrel would probably eliminate that chore, although, you would probably still need to carry a bucket to bring the eggs home. LOL
 
Tom Connolly
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Snowfall...the area I am looking in gets 30" of snow a year, which means about another 3" of water. It would be more if I had a roof slanted at 45 degrees or so because it would collect more snow. Is there some way to use solar energy to melt the snow on a roof so that it would drain into my gutters, rather than sliding off the roof once the lowest layer has melted, forming a "slip and slide" for the snow on top of it?
 
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