By Jay Lund
Imagine capturing some of the heavy rain that has been draining off Northern California roofs lately to water yards this summer, for what will likely be a fourth year of drought.
The drought has generated interest in household cisterns commonly known as “rain barrels” that collect and store rooftop runoff for when it is most needed – during the dry season – to irrigate landscapes and replenish community groundwater supplies. Advocates of these rainwater collectors point to their prevalence in Australia following its decade-long Millennium Drought.
But how cost-effective are rain barrels for individual home and business owners, compared with the more communal approach of adding storage capacity behind a dam upstream?
Here are some back-of-the-envelope calculations:
The cost of household cisterns includes the storage tank, installation and connection to a roof, maintenance and the value of land for the cistern’s footprint. A 50-gallon rain barrel costs about $100, and a 300-gallon tank runs about $600.
The cost of the storage tank or barrel alone amounts to $652,000 an acre-foot of storage capacity (summed over many households). This compares with about $2,000 an acre-foot for expanding storage capacity at large upstream dams.
But storage capacity for water supply is useful only to the extent water is available to capture. Most recent proposals for expanding upstream reservoirs in California yield annual water deliveries of only 5 to 20 percent of the additional storage capacity. In California’s climate, the additional storage space can refill only every few years, implying water delivery costs of $500 to $2,000 per acre-foot of water delivered (annualizing the initial cost at a 5 percent interest rate).
Rainwater cisterns in California might be drained several times during the wet season to replenish groundwater or even out stormwater flows, and once or twice during the spring for landscape irrigation.
For a typical home in coastal California, the annual pattern of storms might allow filling and emptying a 50-gallon cistern one to three times (with considerable overflow possible each time), yielding 50 to 150 gallons a year – less than 0.1 percent of a household’s annual water use in California. For inland homes, the actual water produced would be much less because the rain barrel is capturing runoff that likely would have been used by others downstream anyway.
Indeed, if a rain barrel’s installation removes 8 square feet of a highly watered lawn (1 to 2 acre-feet a year), the gallons saved from reducing the irrigated area would be similar to the water provided by the rain barrel.
So the cost of water supplied by household cisterns in California for landscape irrigation or groundwater recharge could be $11,000 to $32,600 an acre-foot. This is 10 to 20 times the wholesale cost of water in Southern California and 5 to 10 times the cost of desalinating seawater.
While the economics of household cisterns for water supply in California are unattractive, cistern collection systems do provide some environmental benefits. Evening out stormwater flows reduces the costs of managing it downstream. And the prominent display of rain barrels at homes and businesses serves as a constant reminder of the scarcity of water in California, perhaps increasing water conservation more generally.
Jay Lund is a professor of civil and environmental engineering and director of the Center for Watershed Sciences at UC Davis.
Portland’s Regional Water Providers Consortium has a nice primer on rain barrels
American Rainwater Catchment Systems Association has a large collection of additional information.
San Diego posts a Rainwater Harvesting Guide for homeowners.
Alliance for Water Efficiency provides an overview on the history and effectiveness of rain barrels and other useful resources, including:
- Harvesting, storing and treating rainwater for domestic indoor use (Texas Commission on Environmental Quality, 2007)
- A review of applicable policies and permitting requirements for non-potable use of cisterns (University of Florida IFAS Extension, 2007)
- The Value of Green Infrastructure: A Guide to Recognizing Its Economic, Environmental and Social Benefits (Center for Neighborhood Technology, 2010)
Jay, aren’t you forgetting to amortize the costs of a rain harvesting system over their lifetime of use? Then there’s the personal satisfaction that comes from taking action and seeing an immediate beneficial result.
I live in rural southern Humboldt County where rainwater harvesting or winter water storage (filling tanks only during winter) is becoming essential in salmon habitat watersheds impacted by summer withdrawals for cannabis irrigation from springs and small creeks that feed the nursery creeks for coho and steelhead trout. A few model growers have been able to show that it’s not necessary to withdraw any water from their water sources during the summer by using rain catcher tanks, water bladders and small lined ponds.
Different water storage solutions than those of urban and suburban dwellers I know, but one that needs support in northwestern California and other areas where the cultivation of cannabis is impacting summer stream flows.
What about the dust that has accumulated on the roof over a dry spell? The particulate matter, which may include toxic substances, certainly would degrade the value of the saved water and limit its possible uses.
The first rains of the season flush roofs and gutters and there are devices to flush the first rain. After that the water is fine for household irrigation uses, but could also be filtered and sanitized for drinking water.
We have a 100,000 litre rainwater tank (yes, I am in Australia) and have no such problem. Our water is filtered at the kitchen tap. It is used for absolutely everything including shower and laundry. We have no other water. I think people need to see water as absolutely precious. Our grey water from the laundry is treated and sprayed onto the lawn. When you are responsible for (even part) of your water supply it makes you think differently which is a good thing. I am sure California could benefit from people at least trying to gather some water for themselves. 🙂
The other important consideration is that climate models are predicting that precipitation in Fall will arrive later and in Spring will cease earlier. So our past normal four month rain season could shrink to just two months. This means that the wet season is considerably shorter during which cisterns would be valuable “to replenish groundwater or even out stormwater flows”. In contrast, the dry season is longer during which irrigation water is needed and thus the ability of cisterns to provide all that supply is decreased.
The analysis of cost seems a bit too theoretical and not grounded in reality on at least one count. It’s not like people bought that land (cistern’s footprint) to put barrels on. It’s merely that people are making use of that tiny fraction of their residential property that otherwise was effectively going unused or was previously unproductive. I’m not sure there is any opportunity cost there that warrants being calculated into the equation.
Another minor point. . .rainwater is full of nutrients that plants respond well to, whereas the treated crap you get from the tap running from reservoirs does little else but keep plants from drying up.
And what about the cost in energy and externalities (pollution) required to treat and deliver that reservoir water to one’s home?
On a practical level, rather than the professorial theoretical level, the economic cost of my rain barrels consisted of the purchase price of the containers. That’s it! All nutrient rich rainwater was delivered free of charge, no resources used for treatment or delivery, and most of which would have otherwise flowed into the storm drains here in Santa Barbara, collected pollution and toxins a,long the way, and then run into the ocean, exacerbating the fouling of local creeks (home to critically endangered southern steelhead) and ocean waters which sicken and kill wildlife and sicken ocean goers like myself.
None of that water would have ever had any chance of flowing into a communal reservoir upstream.
50-100 gallon rain barrels do not address the issue. How do the numbers look with a 5000 gall tank? That is closer to the Australian norm.
Yes. With a 5,000 gallon tank, you can catch much ore of the roof runoff, and reduce much of the stormwater flow. Some of the “first flush” you might want to let go, as mentioned above. But the large tank will be more expensive and take more space. These things can be penciled out locally to see if they make sense.
Jay, a typical 5,000 or 5,300 gallon polyethylene water tank occupies the same footprint as a 1,600 or 2,500 gallon tanks = 102 inches in diameter, the difference being tank height. Price per gallon of storage drops with bigger tanks.
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I bought four 275-gallon used, stackable “totes” for $500. Let’s say I spent another $500 on materials to connect the downspout to the storage system. I now go into the dry season with more than 1,000 gallons for summer watering. If I operate the system for 25 years, cost is <$80/AF. I have also mitigated my rooftop's contribution to overwhelming the local creek's capacity (if only slightly).
Why does Prof. Lund put out information seemingly intended to argue against doing the right thing? Small scale water storage is an important part of the solution no matter the cost, same as solar water heating and PV for the rooftop. If you can afford them, you should invest in these technologies to save our aquatic habitats and slow climate change.
If it is in a dam, then some radical environmentalist, because we all are environmentalists to some degree, will steal it to feed their ichthyphilia. If it is in my backyard, it is mine and provided it is legal, I can use it without being fined. I lived in California during my childhood and remember using bathwater to flush the toilet. My friend, who unfortunately still resides there, is nervous about overusing water and getting dinged even when there isn’t a drought. Hell, if local officials weren’t so nutty about gray water, it wouldn’t be an issue.
Rain barrels are a money wasting diversion from real conservation. They might work in an environment where summer rains deliver water at the time of peak need, but in California with its winter rains, they are an unsightly nonstarters. The cost is close to $1 million per acre-foot (AF) installed which is a little more than Dr. Lund’s number. That is 50 times more expensive than desal water ($20K/AF of capacity). Please, let’s have water districts concentrate their conservation funding on effective programs. Every dollar spent purchasing or installing a rain barrel is not spent where it can do far more good at $100-300 per AF saved.
Are you looking at the life span of a rain barrel. There are no costs after the initial purchase. Desalination and public water treatment has costs per gallon of water the you pay for every time you use water.
Another aspect to consider is the educational or behavior modification benefit of using rain water stored on site. Someone who has installed storage and is collecting rain water, may tend to use that water more judiciously. Decisions about what to plant, and how much to water and when may be made with a different mindset when the water is coming out of a limited cistern, rather than the “unlimited” tap.
it is not unlimited/free. We pay for it. So we are careful not to be wasteful and spend needlessly.
There are many benefits to distributed water storage systems, particularly when managing for “black swan” perturbations to our system. Our Roundtable produced a nice report on this subject: http://aginnovations.org/images/uploads/CRWFS_Storage_FINAL.pdf
Part of a distributed system should probably include household, farm, or neighborhood scale water catchment and storage systems, and it’d be neat to see some analyses of the economics of different scales of systems (e.g., small backyard cisterns to ponds and very large subterranean tanks). I agree that there needs to be a deeper analysis of true opportunity costs, amortization, and ecosystem service benefits (e.g., reduced stormwater peak runoff).
Lastly, I’ll just mention that my family has ridden out numerous droughts in central Texas relying solely on rainwater for all household water use and some livestock needs. There are a number of interesting “case studies” out there which can be analyzed in a more systematic manner.
I was amazed when visiting Jordan how common it was for households to have rainwater cisterns, some quite large. Like California, their climate is wetter in winter and dry in summer, so I expected rainwater capture to be unsuitable for the place – since you could only get one refill per year for the cistern. Three factors seemed to overcome this problem: a) there was not much other water, with municipal water systems being fairly unreliable (so household water storage was used almost every week), b) the rainwater is much softer than the municipal well-water (and was especially prized for making tea; using rainwater cisterns for potable water would cause much discomfort for American public health officials – and perhaps discomfort for water users as well), and c) overall household water demands were very low (perhaps 10 gallons/capita/day), so a little water goes a long way.
Reading this Swiss cheese-like article from the perspective of a rainwater harvesting professional was a disappointing experience for me. So may holes in it! Beginning with the assumption that all rainwater systems cost as much per gallon as 50 gallon or 300 gallon tanks is itself a red herring and the article goes downhill from there. What is not even mentioned is that currently the Sierra Nevadas are at 30% of normal snowpack and the high mountains of Colorado and New Mexico which feed the Colorado River from which California (as well as Nevada and Arizona) draw much of its water are currently at 60 to 80% of average. Governments can build aqueducts and dams all year long but if there is no water to fill them, dams are not (pardon the pun) worth a damn. Water conservative states such as my own (New Mexico) as well as Arizona and now Texas are beginning to emphasize rainwater catchment, collection, and harvesting as viable options in a time period where droughts appear to have become the new norm. Articles like this pooh-pooh rainwater systems and will discourage people based upon mistaken arguments and assumptions. This is not the right way to go and this entire subject of rainwater harvesting in California deserves a much better and well thought out assessment.
The author brings up good point to why rain barrels are a feel good solution to alternative water sources. They do not hold enough water to be effective during dry seasons, but comparing it to whole sale costs is irrelevant, because the customer are paying and that is where the economic case is made. Water is under priced in many places and the economic case is hard to sell. There is a positive lifecycle cost, but ROI can be 10-20 years. Another factor is the loss of water through evaporation in RHS is negligible when compared to traditional reservoirs.
I see the problem with the rain barrel programs I have seen is they do not seem to teach the people how much water they really are using and it is sold as a cheap solution further depreciating the true cost of water. Have the attendees bring a water bill to the workshop. Most people I talk to about rainwater harvesting use rain barrels as a cheap solution to investing in a true rainwater system which could decrease the domestic water use. They spend extra time cleaning out their systems every year and use chemicals to treat the mosquito problems. A properly designed rainwater system should produce potable water out of the tank. http://www.therainsaver.com/?p=182 Another issue is the loss of revenue for utilities if wide range RH was implements as was done in Australia due to drought. A solution for that is: http://www.therainsaver.com/?p=453
For more information on rainwater harvesting go to http://arcsa.org American Rainwater Catchment Systems Association and my website http://therainsaver.com
Engineers should become involved with ARCSA and take their classes. The design principles and the products their vendor members sell have been used for decades in other parts of the world.
Very interesting to see other types of water collection systems and the pros and cons of said system.
I find the math questionable. I’m sorry.
Yields are far greater than suggested: one thousand square feet of roof yield an average of 8,000 gallons per year in Southern California.
Your math is correct that this much water is often available off of a roof annually, but the article’s math is correct that much less can be captured in a 50-gallon rain barrel.
I don’t see how the math is remotely correct. Please explain. Here is an excerpt;
” For a typical home in coastal California, the annual pattern of storms might allow filling and emptying a 50-gallon cistern one to three times (with considerable overflow possible each time), yielding 50 to 150 gallons a year – ”
A typical home being 1,800 square feet is yielding 1,123.20 gallons per inch of rain ( square footage x .624 ).
The average rainfall in California is 12″ which equals a yield of 13,478.40 gallons per year, on average.
Assume for a moment we have a raging drought and w only get 25% of normal rain.
That is still 3,396.60 gallons in a year.
Assume again that we are collecting1/4 of a typical house in a horrible drought year where 1/4 of the normal rainfall happens….
That’s still 849.15 gallons per year, not the 100-150 gallons the article suggests.
That’s why I say, I don’t get this article at all. It seems to be almost intentionally misleading and I don’t understand why that would be.
As Jay mentioned his statistics are for what “can be captured in a 50-gallon rain barrel”. To save your 849.15 gallons you would have to fill and empty that one barrel 17 times. If you could do that over a whole year that would require one cycle every three weeks. That would be possible if you lived on the east coast where it rains all year long. In California there is typically no rain in the Summer or early Fall to fill your barrel. In the Winter it rains every week or so and thus it is pointless to empty your barrel for irrigation since the ground is still wet or soon will be with the next storm. So maybe there is six weeks in the late Fall and also April and May in the Spring when you can try to fill-empty that barrel. On average you might be able to do that fill-empty cycle three times and thereby save Jay’s 150 gallons.
Your savings of 850 gallons is only possible if you bought a 300 gallon barrel and then fill-empty that three times. But such a barrel will be much more expensive and harder to find a location large enough for installation.
Your math is great, but what Jay is saying is that 50 gallon pickle barrels aren’t going to make a difference. If you’re using the harvested rain in the summer for landscape irrigation and you only have one to three barrels for a typical suburban lot, then your irrigation needs far outstrip your storage. For individual rain water collection to work we need real cisterns, not pickle barrels. Cisterns cost a lot of money. But if you have a big enough back yard you can buy a cheap above ground pool and really make a difference. For example a 5,000 gallon pool costs about $300 online plus freight and a 15,000 gallon pool costs around $900. Cover it with an opaque tarp to suppress algae growth and you can meet your landscaping irrigation needs for the year. They’re kind of ugly, but so is a dead yard.
The above ground pool idea for cheap irrigation water storage is not new, it goes back to the 1980’s in Humboldt County when pot farmers were hiding their plants in the shade of trees to avoid detection by the annual CAMP helicopters who were spotting gardens from the air and drug agents who would walk the creeks looking for the ubiquitous black poly pipe lines that would lead them to the marijuana gardens. The pools could be camouflaged, filled from the creeks and then the water lines rolled up. These guerilla tactics by the pot growers kept 90% of the plants from being eradicated. If a pool got discovered and destroyed, usually the agents just slashed the liner, it was no big loss to the growers because the wholesale price of marijuana was around $3,000 a pound in those days and a new pool would be back in action by the next growing season.
We’re in a severe drought and some old pot grower guerilla tactics by suburban homeowners could save a lot of water, unfortunately it’s almost March and we likely won’t get enough rain to fill storage, so these ideas won’t help much for this summer, but what about getting ready and having a storage system ready for next fall when the rains come back?
I’m a firm believer in rain harvesting and I live in Humboldt County. Despite being the wettest spot in California our creeks where salmon spawn have been drying up in summer due to drought and excessive water withdrawals by green rush marijuana farmers, killing young steelhead and coho. I have a 47,000 gallon rain catcher tank at the top of our ridge that cost $24,000 to install, which was a long range solution for our water storage and keeping our property salmon-friendly. It’s almost full from rain alone and can be topped off from our spring before May.
Although I agree that 55 gallon drums are almost always inadequate by any measure for rainwater catchment systems, where the math is wrong is what the costs are for both these containers and other containers as written into the article. Used blue 55 gallon drums can be found easily in the $10 to $20 range, and new potable grade 300 gallon containers for under $400, which is substantially different than the numbers quoted in the article. Not mentioned is the fact that water tanks larger than 1200 gallons up to 3000 gallons are often priced in the $0.50 per gallon range, and it is these larger storage tanks which need to be placed for an effective system. The bottom line becomes this: water is clearly a precious resource that will be increasingly scarce in California and much of the remainder of the Western USA due to drought and demand. It makes much more sense to promote any type of conservation measure than it does to criticize peoples’ efforts with negativity. Perhaps pointing out that instead of 55 gallon drums, a better idea would have been to encourage people set up systems based upon the square footage of roof areas, proper guttering, and appreciation of aesthetics than to denigrate the entire rainwater harvesting idea. Ironically, the American Rainwater Catchment Systems Association (ARCSA http://www.arcsa.org) is conducting a rainwater harvesting class in Davis, CA from 3-3 through 3-4, 2015. It might behoove the author to find out more about what is being done across the country and in CA so as to gain a larger perspective on what is involved in rainwater collection and how it truly can be both a cost effective and useful means of storing and using water.
One non-economical aspect of rain barrels which should be taken into account but is completely irrelevant to their cost-effectiveness is the value they have on an individual homeowner’s psyche by making them feel that they are “doing their part” to fight California’s drought.
I love the title, the romance thing 🙂 . By the way, how much is the cost for that of rain barrels?
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Thank you for this. It’s nice to have a balanced, data-driven article about the cost effectiveness of rain barrels out there for everyone to see. Plus, I love the title – the romance of rain barrels indeed! <3
Interesting and insightful article. In our coastal area of CA, I calculated the value of the water collected in each 55 gal barrel at about $2.25, based upon total water costs for tap water including sewer and taxes (although roof water is not potable unless treated, it does some benefits for plants.. so maybe it is a wash in terms of value). We don”t get frequent rain (there hasn’t been any significant rain in 6-8 months even after a record snow pack winter) and rain comes in a few major events. So if I get 4 fills, I have saved about $9 per barrel/year for my effort at best. However, I don’t need the water for plants when it is raining in the winter, so hopefully I can make use of the water in between the rains or I will have to forego some of the potential re-fills from rain events that are too close together.
The typical plans for barrels, stands and plumbing start at about $50 and go up from there…including the decorative barrels which go for about $90 just for the water receptacle alone. I figure my B/E on a relatively simple system with my free barrels would be about 6 years assuming we get sufficient rainfall, but since our local water isn’t collected and runs to the ocean it would be a net gain in terms of water conservation for the general good. With that in mind, I’m building a system, but trying to keep the costs down, while making it aesthetic enough not to irritate my wife or my neighbors.
You just need to be mindful and realistic about the economic aspects of rainwater collection for your particular location. Most parts of CA don’t get much rainfall except for a few major winter storms (which is why we need water the rest of the year when it is hot and dry). So, while rain collection is helpful, it is not necessarily a year-round solution in CA like additional storage capacity for the snow pack in the Sierras might be. As others have stated, if you can use larger storage vessels, you can probably improve on some aspects of the economics (but they also may require more engineering and construction costs and large scale systems may not be feasible for the typical residential homeowner here in CA),