Colorado rain barrels

Bad Mom Good Mom sent me a link to an article on rain barrel legislation in Colorado. It's a quick but balanced perspective.


Full URL below:
https://blog.yourwatercolorado.org/2016/06/17/rainbarrels-and-rainwater-harvesting-for-water-conservation-and-stormwater-management/



- Posted using BlogPress from my iPhone

Rainwater Colander

Here's a "rainwater colander", an inline downspout rainwater diverter, a product I first stumbled across at my Home Depot while looking for a downspout extender to better direct rainwater into my garden. It snaps in to your existing gutter downspout (provided you use one that is sized for your downspout). It's "designed to filter out debris in rainwater collection barrels and systems" including surge tanks and "can connect to a garden hose to water plants directly".

The image shown is Amerimax brand, available at Orchard Supply Hardware and elsewhere for around $10 or less.  This seems to be the least expensive that's readily available.

Rain barrels in other places

I saw a rain barrel a week ago that appeared to be completely justified by local weather and usage patterns.

Surge tanks vs. rain barrels IV

I'm sure I left you dangling in a previous installment with the question of how rainfall intensity affects the usability of surge tanks.  I talked about rainfall intensity without actually answering the question, but we can now get to the answer that I am sure you've been waiting for.

A recent discussion on radio station KPCC asked rain barrel owners what they would do with ALL THAT WATER.  The answer was that their tanks were overflowing, they were too heavy to move, and no one knew what to do with the water.  They were talking as if they were going to hoard it for a hot summer day!  It was a gigantic Duh moment, but they were too blinded by ALL THAT WATER  - all 55 gallons of it - to take a leap to the most logical place which is to reject rain barrels and embrace surge tanks.

Meanwhile, a friend who is an actual meteorologist stopped an earlier post in this blog by to say that most 30 minute southern California rain bands could be accommodated by a surge tank.  That's really the bottom line, isn't it? If you can't flow rain water directly from your gutters to some place where it will infiltrate, then it might pay to have a surge tank type of set up. Let's see if she's right with a little garden engineering. 

It's also nice to make some estimates, since the possibility is that surge tanks needn't be gigantic 55 gallon drums and therefore might be more seemly in the garden.

This post is again mostly stream-of-consciousness garden engineering, which I am pretty sure has a limited appeal.  It may also be wrong.  Therefore you may find this analysis simple or simple-minded.

Surge tanks vs. rain barrels III - storm intensity

In order to answer questions that I have about how large a surge tank is needed to accommodate a certain number of local storms, we need to know about rainfall intensity.  Intensity tells us how much rain we get in a unit of time.

Intensity has a simple answer when considering the duration of a storm as your time interval.  If a storm lasts T hours and it drops 1" of rain, then 1"/ T is the average rate of rainfall.  However, real storms of consequence don't behave like that.  Typically they start out slowly, have a peak rate of rainfall, and then taper off.  From what I've been able to tell, there are two main ways to estimate storm intensity: Using a model hyetograph or using Intensity Duration Frequency (IDF) graphs.

Surge tanks vs. rain barrels II

In this post I'm trying to estimate the usefulness of a rain barrel operated as surge tank. 

The valve is open all the time when a rain barrel is used as a surge tank.

This is a bit stream-of-consciousness, and engineering-estimate-like so just skip it if that bothers you.  It could very well be wrong too.  I'm not paid in anything other than pride for this writing gig, so fact cross-checking sometimes gets short shrift.  A little Googling provided the information used herein, and I'm sure you can find similar numbers for your area if you care to.

The first question I asked was how big must a surge tank be to capture rainfall effectively in a downpour?

Surge tanks vs. rain barrels I

 I received a few electronic solicitations to get a free rain barrel from my local water district which I promptly ignored.  As I've noted before, they aren't a particularly good investment for southern California.

However, there are a couple specific exceptions to normal situations in which a rain barrel might be a good use of resources in our climate.  One of those is when it's used as a surge tank.  Surge tanks might sound complicated, but the concept of operations for a rain barrel used as a surge tank is not that different than a rain barrel used as a reservoir.

What can we say about Los Angeles area rainfall this winter?

I've received 8.35" of rain in my back yard this year.  Since I have a few years worth of data on rainfall in my back yard, and decades of data from the nearby Los Angeles area, I feel that I can draw a few conclusions.

1. Rain barrels still suck.  I've said this before and here's a short synopsis of why with the caveats.  This last winter we had 17 storms come through that dropped measurable precipitation.  That's 17 opportunities to catch rain water.  The typical home rain water harvesting setup involves 50 to 100 gallons of storage.  So that's perhaps 1700 gallons of rain water you could have saved and used after the storm has passed.  Go figure out how much that actually saved in money versus the cost of the installation.  I've done that already for you, and it's not worth it.  Wouldn't you like to use that water during the summer on your vegetables?  Don't bother, you can't realistically save 50 to 100 gallons for that long.

Caveats: When storage is abundant (several times the amount of rain that your roof sheds in one storm) then it might make sense.  There are under-house bladders and cisterns that seem to meet that criterion.  When storm frequency is greater then it might make sense.  When storm season is longer it might make sense. If you have occasional summer storms then it might make sense.  The climatic conditions aren't likely to change enough in California even in the face of  global climate change.  Really, don't bother with a mere barrel or two.

2. Rain water retention still makes sense.  When you are storing the rain in the ground (eliminating run off using swales, or rain gardens, or permeable hardscape, or however you do it) then it's easy to store large amounts and you don't have to fuss with infrastructure costs or maintenance other than your garden.

3. This winter was typical for Los Angeles.  Everyone's crying drought, but the native plants living locally got a normal amount of rain.  Do you think this is surprising?  The most frequent amount of rainfall that the greater Los Angeles area gets is 8-10 inches per year.  Over the past decades of rainfall data that I've analyzed, we received 8-10 inches of rain in 16 of them.  For comparison, we received 6-8 inches of rain in 8 years, and 10-12 inches of rain in 9 years.  Folks, the LA area is RIGHT ON TARGET for the rain we received this year.  It's dry here, but for our native plants THIS WAS A NORMAL YEAR.  Let's not try to make Los Angeles a subtropical paradise by importing water and concentrate instead on showcasing our California paradise.

Rain catcher design proves too costly

I'm looking at arbor / pergola and trellis designs that I like and collecting them over on Pinterest.

Follow Brent's board Arbors and Trellises on Pinterest.

This one from Lowes caught my eye because it is simple and has a number of design elements that I might like to consider.  It also has a bill of materials and costs for each part of the construction.  Overall, this is just the sort of useful garden construction advice that I like to see online.  Bravo to Lowes.

However, one of the design features of the arbor is a "rain catcher" which is a section of 6" PVC pipe stood on end and fed by a downspout.  Go to the article linked above to see the construction details or just take my word for it. The BOM is reproduced below showing a total price of $125!!

Rain barrels schmain barrels

Someone else has cottoned to the fact that rain barrels are a gyp. Though I've not previously heard of Owen Dell, he seems to be a well-respected enviro-writer who is "master of the craft: Landscape architect, educator, and author". Thanks to Emily Green (previous link) I became aware of some of his recent writing where he calls bullshit on the cult of the rain barrel, using the generally-higher-rainfall-than-Los Angeles area of Santa Barbara as his point of reference.

Of course my reader already knows that rain barrels don't get the job done due to my insightful series of articles on the cult of the rain barrel.

Go and read Owen's blog and skip to the part where he writes rain barrel suppliers for more information:

Hello,

I have a 7,500 square foot lot, and I use about 140,000 gallons of water per year for landscape irrigation. A single 60-gallon rain barrel will supply 0.00043 of my annual water needs, making it necessary for me to have 2,333 barrels to meet those needs. They will fill almost a quarter of an acre of land if placed side-by-side. My lot is only about .17 acres, and the house and garden take it all up. Do you have any suggestions? Thank you.

The responses are illuminating.

Worldwide cost of tap water

Water is too cheap!

A little further down in the blog when I conclude that rain barrels are only the leading edge of a water public relations campaign and that they only make sense if they are given away free, I made a casual comment that water is cheap. "Tap water costs next to nothing" is the exact quote from my most recent Rain barrel vs. soil rant. A comment from Diane of Food, Fun and Life in the Charente was that tap water was too expensive to see extensive outdoor use in France and the UK.

Wikipedia supports this, citing 6% of total residential water used outdoors (lawn watering and washing cars) in France. This is much lower than California (The Metropolitan Water District of Southern California estimates that, "in hot, dry areas, landscape irrigation can account for as much as 70 percent of the summer water use in single-family homes."  This is probably a histrionic upper limit for PR purposes, but it can still serve as a point of comparison: 6% is a factor of 10 less than 70% so the real numbers are probably not in alignment either.) But is it really a cost issue that keeps outdoor water use in France much lower than in southern California or is it a cultural and horticultural issue?

Rain barrel vs. soil

You are a rain barrel stud, but you're beginning to feel a slight unease. Your sense of equanimity is a little disturbed because you've been reading this blog. You figured out that tap water costs next to nothing, so the $500 you spent on rain barrels is beginning to chafe in your tender areas - not only is there no benefit during the majority of the year when we have no rain in our Mediterranean climate, but the barrels aren't the most aesthetic or space-efficient addition to your yard. You want to do the right thing for the environment and a casual survey of your yard during the last rain storm suggested that next to the quantity of rain running off your driveway and out to the street, your rain barrels were looking a little...paltry.

Magical rain barrels versus the world

I've previously talked about the kind of collection efficiencies that rain barrel users can expect.  They are typically dismal unless you have a very large barrel or the right kind of rainfall pattern.  Collection efficiency depends on the rainfall pattern since one large storm would overwhelm most storage systems, thereby wasting the majority of the rainfall whereas a large number of small storms might never once overflow a typical barrel system. In the latter case efficiency would be 100%.

Based on typical southern California rainfall patterns I estimate a typical rain barrel collection efficiency at 10-20%. This is based on my previous analysis after throwing out the highest and lowest rainfall years and applying a factor of two reduction in efficiency, since the numbers I calculated were best case, and nobody is that diligent. Susan Carpenter of the LA Times spent $500 on two rain barrels and received a third for free.  If the roof area she captured rain from was 1500 sq ft, then her cost per square foot would be $0.33 for 10-20% efficiency. She was happy to pay it, and I guess that speaks to the psychological impact of having a seemingly large amount of water deposited, as if by magic, in your barrel.

But is 100% efficiency achievable and cost effective? Yes, just about.

Magical rain barrel psychology

In earlier posts I first exposed the cult of the rain barrel as a marginally efficient sop to green guilt but then had an Ah Ha moment in the second post when I related the prevailing theory of how unengaged people will become engaged people through the magic of rain barrels.

The magical rain barrel theory says that Flo and Joe Sixpack will suddenly throw off years of disengagement and disregard for the environment after receiving a free rain barrel from the City of LA(1) After work Joe will park his 4WD full sized truck in the lot-length driveway of their 50's era SFR, amble over to the rain barrel, and switch on the irrigation for his organic free-range tomatoes. He'll share the tomatoes down at the local VFW Hall and, over cold Budweiser, tell the story of the enabling technology of the rain barrel. In doing so he will spread the true gospel. It'll be viral!

FAT CHANCE.

This theory only works on people that are already on the cusp of wanting to do something green. Among LA's west side population I'll take a guess that fraction is at most 5% of households. So if you want to make inroads in 5% of households, go ahead and give out free rain barrels. Heck, I'll take one, though even on my somewhat capacious lot I don't know where I would conveniently keep it. On second thought, cancel my rain barrel. Just send me a crew of workers for a weekend to redo the drainage in my yard to more effectively infiltrate water on site.

What sorts of efficiencies push people's buttons and get them excited and engaged? Hardnosed reporter Susan Carpenter, the Realist/Idealist of LA Times was so thrilled with her $500 investment in 3 rain barrels that she put it at number three on her top list of green innovations. She lived with them for the past two to three years and based on my guess that her roof was larger than 600 square feet, she was probably getting rainwater collection efficiencies no better than I cite in my first blog post - 20% to 47% (her roof is larger but her total barrel size is larger too so these numbers are educated guesses for sake of discussion). But because no one is as efficient as the hypothetical water stud in that post, let's assume Susan had an actual 10% to 24% efficiency out of her rain barrels. She says that it lasted her a month into summer.

And she got excited! So here's a person with green tendencies, presumably somewhat skeptical (she is a Realist, after all) getting excited over an outlay of $500 that netted one less month of watering their fruit trees in summer.

I guess magic does happen.

---

1. "The City of Los Angeles, Department of Public Works, Bureau of Sanitation, Watershed Protection Division (Stormwater Program) rolled out the City’s first free Rainwater Harvesting pilot program in July 2009.
Residents that sign up for the program will be eligible for complimentary installations of (1) rain barrels (2) downspout disconnections, or (3) custom-made planter boxes for businesses. The captured rainwater will then be either routed to pervious surfaces or used for on-site irrigation."

Rain barrels redux or Why I can now live in the same world as rain barrels

In a previous post I calculated some optimum efficicencies for rain barrels in sizes of 55 gallons and 110 gallons  in support of my feeling that I don't really care for rain barrels.  After I had calculated their efficiencies I still wasn't convinced they were a good idea.  Today I had the opportunity to ask a garden professional about rain storage and rain barrels when I attended an Ocean Friendly Gardens Hands On Workshop.  More on the HOW later, since I know you are all so interested in this garden professional's opinion on rain barrels.

She said, "Rain barrels are the gateway drug to an ocean friendly garden", as near as I can recall.  Just as I already knew, just as I already calculated, and just as the workshop today taught, soil is the preferred method of water catchment.  But for those who live in blissful ignorance of their impact on downstream flow, rainbarrels raise awareness in an effective way.  The rain barrel owners get engaged and that engagement leads to even more effective changes on their properties.  Oh, and if you have a vegetable garden or some area that needs a bit more water like fruit trees then by all means use a rain barrel if it meets your space and aesthetic requirements, They do after all provide soft water for free (ignoring the initial costs).  But don't look to even a couple 55 gallon barrels as your primary line of defense in a water wise garden.


That was the gist of the insight that I received today, which was well worth the price of admission (several hours of my time plus I learned a few other things).  Ahhh...Finally, a rational thought on rain barrels.  Given all the hype, I was losing hope that it was out there, but was.

Why I don't think rain barrels are a good idea

You are a rainwater stud or studette! You are such a rainwater stud that you operate your rain barrel in a way that any time there's a day of rainfall you have an empty barrel ready to capture your roof runoff. You feel proud because this is a highly efficient way to manage your rain water. In fact, it's nearly the most efficient way to use your rain barrel.  You're so good that even if we have several consecutive days of rain you manage to have an empty rain barrel at the start of each day. I don't know how you do it, but this is what makes you the rainwater stud. At the end of the wet season, how many gallons of runoff have you saved?

I'll try to answer this question and others as I dig into rain barrels in an effort to convince myself that they are a good idea.

There's good instructions on the web for sizing and building rainwater catchment systems. The more comprehensive ones have disclaimers such as, "However, rainwater harvesting for landscape irrigation may only be practical in locations where rainwater can be collected in sufficient quantities during the time that it is needed," which I pulled from the linked web page (from Texas).

Susan Carpenter, the Realist Idealist of the LA Times ranks her three rain barrels third on a list of good eco-innovations - right behind gray water and solar photovoltaic panels and ahead of earthworks (passive garden design to capture rainwater), the Australian waterwall (a narrow rectangular rain barrel that looks like a wall), edible landscapes, and composting toilets. See Composting toilets, backyard chickens and waterwalls: Susan Carpenter's eco-living experiment

She spent $500 ($300 for two rain barrels (a third was free from the city) and $200 for installation and parts) and writes of the rain barrel experiment,

I was a rain barrel skeptic before I joined L.A.'s rainwater harvesting pilot program last fall.... Though rainwater holds such enormous potential for supplementing Southern California's dwindling reserves of imported water, rain barrels seem like such thimbles. During a normal L.A. winter, my 1,500-square-foot roof generates 13,500 gallons of water — a tidal wave compared to what a little barrel can handle.

Which is my concern exactly, but I don't think that under most circumstances that it's best mitigated by her next observations:

Having lived with rain barrels for a year, I've learned that their small size makes them manageable and affordable. The water they catch isn't stored only for summer use. It can be drained in between rains to water nearby plants. An added perk: reducing storm-water runoff to the ocean.

...The 175 gallons they hold were a lot more useful than I'd expected for feeding my exceptionally thirsty fruit plants. The water they held lasted about a month into the summer.

Under certain circumstances (for instance, your roof drains to unavoidable hardscape and then directly off property) I can see a benefit of rain barrels, but for the vast majority of suburban homes I can't see the ecological benefit over garden infiltration.  There will almost NEVER be a cost savings if Ms. Carpenter's costs are typical: $500 for three unsightly barrels?



Let's try to put some numbers to my misgivings.

Let's assume that you, the rainwater stud, have 600 square feet of roof (half of a modest sized suburban home's roof area) and a 55 gallon rain barrel. Then it would take about 0.15" of rainfall to fill the barrel (using a conversion of 231 cu. in. per gallon). That means that after 0.15" of rainfall any additional rain is not captured!

Looking over the last six years of rainfall information in my own LA-area backyard (One of my not so private obsessions is rainfall statistics.  I'm using my daily records of rainfall to make the tables below.  You can do the same thing with a modicum of effort, an Excel spreadsheet, and the daily rainfall tallies for your area.  Note to Steve Libby: Naturally I predicted the statistical utility of this data years ago when I started recording rainfall :-)

I'm also assuming I made no mistakes with the analysis, something that has not always proven to be the case, but the numbers seem to be what I expected and time is growing short so with an arrogant tip of my nose I'll take the "meets my expectation" observation as confirmation that they are indeed correct. Most of LA and a wide area of coastal southern California should be similar to what I present below. In fact, the inclusion of our driest year (06-07) and our wettest year (04-05) probably bounds the calculation for most of southern California: you should have results no worse and no better than predicted in those years.

Finally, with caveats and rambling prose out of the way, I can make the assessment of the impact that a rain barrel would have had on the rainwater stud's runoff, had he or she sited it in my backyard in any of the preceding six years:

There are two cases below. They use identical rainfall patterns (that of my back yard for the given years) and identical roof area (600 square feet). They differ in the size of the rain barrel. [Note that the number of down spouts doesn't matter.  I assume ALL the rain from a 600 sq ft roof goes into the barrel or barrels.  I'm writing this parenthetical note in response to a comment I received elsewhere suggesting that I add downspouts.]  The upper table gives values for a 55 gallon rain barrel and the lower gives values for a 110 gallon rain barrel. In our recent wettest year, 2004-05, a 55 gallon rain barrel would only have been 11% efficient at capturing rainfall but would have been 65% efficient in our driest year (2006-07). For the case of the 110 gallon rain barrel the numbers are 19% and 99%, respectively. Average efficiencies are 0.47 for 110 gallon rain barrels and 0.29 for 55 gallon rain barrels.

55 gallon rain barrel, 600 sq ft of roof

110 gallon rain barrel, 600 sq. ft of roof

I have to admit that the efficiencies are surprisingly high, particularly with larger capacity barrels.  However, our assumptions tell us that our rainwater stud isn't always using the water when it's most needed in the garden, which is between storms.  Instead, over consecutive storm days that exceed capacity the barrel has to be drained to get the kind of efficiencies that you see here: you actually would have to water with your barrel while it was raining in many cases.  Consider also, that 600 sq ft of roof is only half of a small 50's era SFR roof.  For larger homes the runoff will increase in proportion to the roof area driving efficiencies down for the two cases set forth above.  I'll leave this post as it is now, with a high likelihood of a return visit to this topic later when I can stand to think about this again.

More locally-relevant information about rain barrels is contained in a fairly thorough document that does not address rain barrel efficiency at www.larainwaterharvesting.org.