With the whole world talking green, that the word ecology breaks down into the Greek roots eco and ology, or “home science” may not be news to you. But humor me as I take the moment of launching my Rainwater Harvesting Construction Guide to consider the outer potential of rainwater harvesting as part of an all-inclusive home-science strategy. Even if the scenarios explored here never happen I’ll ask you to let them stir your imagination, move you anyway. With that alone as MLK and JFK can attest, we’re already halfway free and halfway to the moon. The journey of a thousand miles begins right where we’re standing and its imagination that collects the compass, chooses the road, guides the first step and calls the muses in.
The cost of household water:
- At least in LA, has doubled in the last 12 years with no end in sight and has skyrocketed since 2002 when claims on the Colorado River began to exceed the river’s entire flow.
- Will likely increase as rainfall becomes more erratic with climate change and cities and their vendors trying to cover the risk.
- And is currently kept artificially low by government subsidies that may not last as the US dollar and political system face the road ahead. Consider that residents in Guatemala City would pay $1,700 for the water people in Washington DC pay $350 for.
So a multi-barrel system built on the ultra-cheap might buy you a few extra nights out over the long haul with more nights every year, but I’m guessing it’s not the nickels that have got you reading this far, and dimes don’t really inspire journeys to the moon.
The real question I suspect many of us would really love to answer is “What difference can DIY rainwater harvesting make,” and the answer involves a different set of numbers and the big D-word – it “depends.” That said, even dropping a $20 craigslist-score barrel under a downspout and using it to water an existing steroid-pumped lawn would mean importing a few hundred less gallons of water every year and cutting municipal infrastructure a tiny bit of slack.
But I for one love to play big too. So, hearkening back to my days working on the Los Angeles Integrated Regional Water Management Plan, I dared myself to take it all the way. I asked myself, “Could the city that inspired Chinatown meet its needs just from what falls on it from the sky?” Even if the answer comes back as a definitive no, we might learn big.
That’s what we call a thought experiment, and as with any experiment, there are rules to the game:
- For the moment we’d set aside considerations like social inertia, political drama, red-tape, building and social conventions, hours spent in traffic and busy, busy lives. To simplify the game, we’d just look at the goal as a design problem. Show hope of solving the design problem and it becomes worth looking at the much stickier, all-too-human rest of it.
- The teeming semi-desert Megacity of Angels would have to solve the problem through distributed DIY possibilities within the existing built environment. No gutting neighborhoods or $20-billion canals.
- We’d only look at households. Yes, agriculture uses most of the water and commercial properties use water too, but if we’re resourceful enough to become aquatically solvent in the household, we’d be one step closer to resourcefulness and solvency at work and on the farm.
- The City of Angels would have to become water solvent without sacrificing its material standard of living. No living like Third World refugees and no spin-the-bottle to see who gets to shower.
- For now, we’d just look at the yearly numbers. The seasonal timing of things makes a critical difference, but we’ll look at the low-res now to see if it’s worth going high-res later.
- And for now, we’ll just look at the average rainfall year. Even if we don’t cover the nut for low rainfall years, we’ve come a very long way and can perhaps begin to think bigger than the next bottleneck.
Next in the spirit of gaming, come the variables that establish the field of play:
The thought experiment begins in the flat Mid-Wilshire 90019 zip-code with an average yearly rainfall of 15 inches and zooms in on a hypothetical 7,500 square foot lot, say 100 feet wide and 75 feet deep. There’s a house on the lot with 1,000 square feet of rooftop and a family of four living inside.
Why these numbers? Well, the LA Department of Water and Power uses zip-code, lot size and family size to determine water prices. The Shortage Year Tier 1 allotment for our imaginary friends would be 26.35 Hundred Cubic Feet (HCF, 1 HCF = 748 gallons) per two months in Low Season (May to October) and 20.4 HCF for two months in High Season (November to April). This adds up to about 105,000 gallons per year and 287 gallons per day. In 2012, the family would have paid $3.70 per HCF for their allotment and $5.92 per HCF for anything more. If they’re an average American family, they fit squarely in Tier 1, using 73,000 gallons of their 105,000 and paying $361 for the water.
Knowing what those 73,000 gallons are used for then gives us the goods on solving the design problem…. In Permaculture parlance, we say “observe” and also “the problem is the solution” and it doesn’t take a rocket scientist to figure out that the two ideas go hand-in-hand. Below are national averages reported by the National Academies Water Information Center (click here). The outdoor use varies by region and season, but we’ll go low-res with the yearly national averages here.
Right away, rainwater harvesting wouldn’t cover the current total household use even if we could somehow catch and store everything that fell on the whole lot. With 15 inches of rain, the property only gets 70,000 gallons in an average year. We’re already 3,000 gallons shy.
A whole systems approach to the rescue then, and first goes the toilet. The toilet uses 10.9% or 7,972 gallons a year. Convert that to a composting toilet and get extra goodies like carbon-sinking black earth for the gardens, and if enough people converted, way less pressure on the decaying channelized streams-cum sewer lines like the LA River, filtration plants and the ever stressed water quality budget. Maybe enough pressure-release to de-pave the river, turn it into a park and turn the park into the backbone of a food forestry network with all the black earth we’ve got in 6 months, while ending algae plumes and itchy surfers off the Santa Monica Pier. The family’s yearly water score drops to about 65,000 gallons.
Paired with a conversion to eco-friendly household products in the shower, bath, kitchen and laundry, the next move is to run the used, grey water from faucets, shower, bath, laundry, dishwasher and the mysterious “other” through the garden. Now that water, all 18,000 gallons of it, 24.3% of the family’s total use gets used twice before leaving the property but counts only once for the new score for the year, 47,000 gallons. Outdoor use is down from 42,000 gallons to 24,000. Assuming the grey water system is well designed and doesn’t require a bank of levers to operate, there’s no loss in quality of life – and most of the worst household waste has been tamed before it hits the pipes. Any algae plumes still hanging off the coast are done for.
Then it’s down with the leaks. Nearly 6% of water lost through leaks? Some leaks are unavoidable. Pipes age, foundations move, kids happen and with all the proverbial leaks in life, busting out the plumber’s wrench for a weekend ends up low on the totem pole. But say the family goes for it and cuts the 6% to 3%. So much for 2,000 gallons lost per year. Average yearly use: 45,000 gallons.
Now with a much lower bar to hit, let’s see what sort of dent rainwater harvesting can make.
First we’ll look at two types of rainwater harvesting that we might distinguish as “hard” and “soft.” The hard variety refers to the tank, barrel or tub kind of rainwater harvesting, and we could say that the soft variety refers to that which can be theoretically started, if not always finished, with a shovel. The two varieties work best in tandem starting with a hard system that blends via an overflow or “spillway” into a soft system integrated throughout the whole property.
The imaginary property has a 1,000 square foot peaked roof. With a 220-gallon system on either side of the pitched roof and the right gutter arrangement, the whole roof can be collected from. With 15 inches a year we get the potential harvest of about 7,500 gallons with 440 gallons of rainwater able to be stored at once. In the ideal world, 15 little one-inch storms would fill the tanks during the wet season with enough time between to empty the tanks out completely every time for a steady flow. That’s unlikely of course, and that’s where integration with soft harvesting comes in.
Land contouring forms the essence of soft rainwater harvesting, and within well designed land contours, opportunities arise that we… and nature when we’re not around… can put to great use. The name of the game is to keep water on the property and keep it moving slowly, to think of the whole rainwater harvesting system, hard and soft, as a watershed, and doing so can inspire a whole host of possibilities.
It’s worth noting that standard American landscaping flows to a different drum: get water off the property as fast as possible. Hence we’ve all been trained to believe that gardening means running the sprinklers incessantly and still expecting parched soil by June, while the downspouts from the roof generally give the roof runoff a one-way concrete-lined ticket to the ocean. It may seem surprising that just flipping the landscape lens from convex to concave in key spots, that thinking in terms of bowls instead of hills can change everything until you actually see the results with your own eyes.
Since that perfect series of storms is unlikely, we’ll link the hard system’s overflow into a soft system on the property, essentially running its overflow into bowls, swales and other uses so we still get good and more gently distributed use of the 7,500 gallons the hard rainwater harvesting system nets us. Now with the hard rainwater harvesting and the grey water outputs we’re only taking 16,500 gallons from city mains for outdoor use – remember we started out demanding 42,000. Even taking the seasons into account, we’re doing well, since the grey water output isn’t going to change much month to month. Total demand from the city is now down to about 35,000 gallons, half the original 73,000.
At least in theory, the soft rainwater harvesting can take the numbers down a lot further. Bowls don’t accumulate just water. One year of leaves from deciduous trees can form mulch mats that hold water underneath and keep soil processes unfolding for months, even in the hottest weather. Add a 6 inch layer of straw and the ground’s wet all summer. Gardens flourish in the dips and perennial water sinks develop virtuous hydration cycles with increasing mulch, fungal mats, plant diversity, birds and happiness all around. Shape the concrete driveways and patios to direct water into the bowls or replace these hardscapes with permeable inlays and we could argue for hard and soft systems keeping 80% of rainfall in productive use on the property for much of the year. That’s 56,000 gallons of water. On a relatively flat lot sculpted for soft rainwater harvesting and productive soils, we’ve got a 14,000 gallon outdoor surplus for the year.
We’re still pulling 18,000 gallons from the city main for potable indoor uses and the occasional car wash, so I’m not calling the game won just yet, and for many of us, this would be a great stopping point. Extrapolated over the whole city, the low-res joyride has cut water imports and bills by three quarters with no loss of quality of life, a good part of the difference made with hard and soft rainwater harvesting in tandem. Even if in real life we got only a third of that result, we might still win the consolation prize – whitewater rafting for everyone down the Colorado River like in days of old.
And for those of you who really want to finish the job and take the score down to zero, I say start with the Rainwater Harvesting Construction Guide, Power to the Makers! and don’t stop there. The answers are out there. Clay cisterns were such the rage in Biblical Jerusalem that they were a favorite metaphor in parables and Jeremiah even did a jail sentence in one. Here too is a pic of the adobe Earthship that shared our space at Grassroots United in Haiti. The entire roof is a rainwater harvesting system and the water harvested gets used for 3-5 purposes before leaving the surrounding grounds.
With all due respect to Chinatown, I for one will risk my hat over yonder barrel and say that at least as a pure design problem, zero’s a winnable game. Just figure it’s 1962 and I’m asking, can we get to the moon? Only this time, we’ve got the hive mind of the internet too and I’d love to hear all your bright comments for making up the difference.
Thanks again and take a peek while you’re here…