Rainwater harvesting: to require or not to require
This week, the DJC ran an excellent article from Arthur H. Rotstein with the Associated Press called “Commercial projects in Tucscon must start harvesting rainwater.” The article says that the Arizona city has enacted the nation’s first municipal rainwater harvesting ordinance for commercial projects. The ordinance requires developers building new business, corporate or commercial structures to supply half of the water needed for landscaping from harvested rainwater starting next year.
Apparently, landscaping accounts for about 40 percent of water use in commercial
development and for 45 percent of household water consumption in Tucson. That. Is. Crazy.
The article also mentions that a half-dozen other communities in Arizona are looking at replicating the approach, and that rural Santa Fe County in New Mexico has required harvesting using cisterns or similar structures for commercial and residential development since last year.
Which brings me to the next question: why isn’t this a requirement everywhere? Water is cheap, yes. But even though it is cheap, it still costs money. If Tucscon - which the article says gets 12 inches of rain a year - requires rainwater harvesting, why don’t we? (Other than little details like the state owning the rain that drops down from the sky….)
Now I know Tucson and Seattle are very different. I know Tucson uses so much water on landscaping because the city is in a desert, which means for most anything to grow, it is going to need extra water. But the underlying principal is the same. Water is a free resource. When water falls on the ground, it flows along roadways, picking up dirty icky things like metals and nutrients, eventually ending up in a water body like the Puget Sound, where it
does real damage or at a treatment plant, where it goes through an extensive process to get clean. So why don’t we, as a country, require that at least some of that water is captured and used for something productive?
It just seems like a really wasted resource.
Where am I wrong here? Please tell me why this would not work.
By the way, water is going to become an even greater issue of importance as more people move to the Pacific Northwest. I wrote this article a couple weeks ago that discusses the challenges between the desire to get off the water grid and traditional infrastructure.
In that story, a number of experts from our region discussed where we are going with water treatment and the difficulties that lie ahead. It covers a range of opinions but all speakers could agree on one thing: water needs to be more expensive for change to happen.
Kurt Unger of the Department of Ecology pretty much spoke for the crowd when he said “Water is too damn cheap… We need to assess a fee on water to enable so many more things to happen.”
Tags: Seattle, Washington State Department of Ecology, Water, water efficiency
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July 17th, 2009 at 10:18 am
you say:
“Water is cheap, yes. But even though it is cheap, it still costs money. If Tucscon - which the article says gets 12 inches of rain a year - requires rainwater harvesting, why don’t we?”
One answer to this is, that rainwater is not free. Rainwater harvesting systems cost money, and strictly in terms of financial criteria like payback period, such systems do not presently pay for themselves given what we pay for water here.
A second partial answer here, is that we have a rainwater and snow-harvesting system already, which is our municipal water from the Cedar and S Fk Tolt watersheds. For maybe 9 months of the year those systems have more water than they know what to do with, which is to say, they spill far more water downstream than they divert into our municipal consumption.
The big question, then is, what does that rainwater cistern do for you during the ~3 droughty months of the year, when our municipal systems are basically functioning on stored water drawing down the cedar and tolt reservoirs? The answer is, for a reasonable-sized 5000-gal residential cistern, that it will be exhausted–completely drawn down–in one month. So you still have two droughty months where you have to irrigate with city water.
A better solution is simply to not water your garden–to plant natives that are adapted to our climate. And let your grass get brown.
Just as the cleanest form of “clean energy” is conservation, the cleanest (and far the cheapest) form of domestic water is conservation.
July 17th, 2009 at 11:39 am
There is some excellent reasoning above, but don’t forget that all the water we flush, wash our clothes with, and irrigate with from the city system had to go through the whole treatment process, which is fairly energy intensive. So even during the rainy months, if you can use collected rainwater instead of city water, there is a net benefit.
July 17th, 2009 at 12:43 pm
You both have great points. Kevin, I was waiting for somebody to bring up the cost of rainwater systems from their own perspective, so thanks for doing that. The snow-harvesting system is also an interesting point. And yes, native platns, not watering your lawn and letting it get brown is a great answer. But while this region has a lot of environmentally-minded people, it’s also got a lot of gardeners. Somehow I doubt the brown lawns will work for them.
And Nate - you also have a great point. Water treatment is an intensive process, especially considering that much of the water in Seattle that we use for relatively clean functions like washing clothes, dishes etc…. gets dumped into the same system our sewage does after we have used it, requiring even more energy to clean it. One would think there would be some way to capture and re-use that water locally without adding major new infrastructure.
July 17th, 2009 at 1:31 pm
re nate’s comment:
yeah, I think I’d agree that there is a public benefit there. And one might also argue also that if there were a lot of these cisterns out there they would reduce peak urban runoff. We know that built-up areas lose the sponge-like properties of more natural areas and they have flashy runoff, and urban storm runoff is hard to treat and full of contaminants. So the tank on the roof would to some extent compensate for all the asphalt and impermeable surfaces which have destroyed natural water storage.
I think that in our climate you have to argue for some benefits in the rainy season to make this attractive. And uses tied to things like washing or toilet flushing, which are not seasonal. If your argument is irrigation, then your benefit is like one month a year–you’re not going to be irrigating in the 9 months where there’s plenty of rainfall, and in 2/3 of the dry months your cistern will be empty.
I think also that if you do not irrigate–that if you’re talking only non-potable domestic uses–you could probably last through the whole dry season without running a reasonable-sized tank dry. It’s just the usage pattern of irrigation–maximum demand when there is naturally the least water–is by its nature really expensive and high-imact, since storage is expensive in multiple ways.
July 18th, 2009 at 10:04 pm
So. . .in the greenwood area impervious surfaces are reducing the groundwater level in the former bog which has a tangible effect on the home/business owners who are seeing their structures settle.
It is my understanding that SEPA’s are now required for new construction to show how the new construction won’t further lower the water table. At least in this area it would make sense to harvest water either through cisterns, detention basins, or some other means to help infiltration.
July 20th, 2009 at 11:05 am
I will agree that the main reason you do not see more rainwater harvesting in the northwest is that water is to cheap. But there are other factors. A big one is the legal issue. The current laws on the books regarding who owns the water, what is beneficial use, and what constitutes consumptive use are vauge and confusing. The result is that many large scale rainwater harvesting systems do not even get off the drawing board due to fear of legal action or a long drawn out permitting process.
Storing and delivering potable water to a site takes a lot of energy. In order to store it, keep it clean, and convey it to a particular location at the volumes that municipalities deal with uses enormous amounts of energy. If we can reduce the amount of potable water we use……We reduce the amount of energy we use…..Which then reduces greenhouse gas emissions…..Well, you get the idea. It is all connected
In regards to the irrigation issue. Even native plants need supplemental water in our northwest summers for establishment. If you want your garden to be green, irrigation is crucial. A 5,000 gallon tank combined with a drought tolerant planting design (with very little lawn) can last most of the summer. It does not necessarily empty in one month as mentioned above. Although, storage is a big issue. Finding the money and space for a 5,000 gallon cistern is not easy, especially in a urban residential lot.
July 20th, 2009 at 11:42 am
I agree concerning the collection and storage of rain water in the Pacific Northwest. Storing the amount of water needed to get through the drought of our summers requires a huge storage tank. Designing your landscape using drought tolerant plants (not necessarily native plants) and using a good layer of mulch reduces the need for supplemental water during the summer months. But the big factor is the cost of and having the room for storage tanks.
I live on a typical lot in West Seattle and have three rain barrels. Usually I run out of water by July. Cost is another factor. You don’t save rain water to reduce the cost of water. A full rain berrel holds about $.17 worth of water. It would take about 18 years to get your investment back from the purchase of a rain barrel.
August 5th, 2009 at 1:17 pm
Great post, up here in the north west rainwater harvesting makes some sense because of our frequent rainfall, however town in AZ, the rain is so minimal, running any type of irrigation system would quickly deplete the reservoir. A greywater recycling option would be a better choice b/c it is a reliable resource. Katie, if you get a chance could you re-post this post (and any future posts) on our water harvest community site? http://www.waterharvestonline.com I know there would be people in our community who would love to read this post. Thanks and keep it up!!