Oh, those crazy kids -- what have they done now? Well, they've single-handedly brought back the 2-silo farm in Concord, haven't they? This used to be a common arrangement: a barn with two silos. The last one was at Triangle Farm on Spencer Brook Road, but at least one (if not both) of the silos were torn down in the past couple of years. Happily, the magnificent barn remains... but I digress...It began with a friend from the Concord Discussion List noticing an ad on Craig's List for the sale of two used 850 gallon water tanks. "Honey," I said. "We really don't need two 850 gallon used water tanks, do we?" "Of course we do!" my husband said. "Let's buy them immediately!"
Having increased our garden four-fold over last year, but neglecting to increase our rainwater holding capacity, I capitulated. But 1700 gallons of water? 6' wide by 10' tall? Mon Dieu!
Well, we bought them all right. The seller delivered them on a Saturday, depositing them on our front lawn. The astonished rubbernecking by passersby got so bad, we had to move them to the side yard lest our neighbors incur auto accidents as they innocently drove by, not expecting such objects to be in our front yard.
They were FILTHY. They had been used to hold well water in a car wash, and they both had algae and hard water scale inside, plus on the outside the accumulated exhaust deposits from 10 zillion cars as they were washed. It took Rich four hours to pressure wash them inside and out.
It turned out these babies weren't 6'x10' -- they weren't even 850 gallons each. They were 4'x10.5', and just about 1000 gallons each! All good news, except that the clearance under our eaves was just a hair over 10', which required the tanks to be recessed over a half-foot below grade to place them at the most convenient spots to gather rainwater.This Wednesday -- and with no little effort, aided by some kind neighbors -- we lifted the last second onto its feet, the first one having been placed the day before. Thus the 2-silo farm was established! Rich attached them to our gutters, and the filling began. By twilight on Thursday, we had collected over 1000 gallons from the roof of our 20'x50' house (the rain gauge below right shows approximately the precipitation during this roughly 24-hour period). This was in addition to the 550 gallons we had on hand already in the two 275-gallon rain barrels we took on last year -- also repurposed tanks.
We now have a total of 2550 gallons in rain water holding capacity, which sounds like a huge amount, and it sounds like that should be more than we will ever need in an entire season. But let's pause a moment and think how much space it would take to capture and store one year's worth of rain as it falls upon our 1000-square-foot roof. I happened to stumble upon this page discussing how to calculate rainwater storage space, and son of a gun: though it's from California, it happens to use our EXACT conditions in its example. Forty-two inches of annual rainfall (the Boston area average) on a 1000 square foot roof! Assuming an 80% efficiency rate, our little abode collects 21,000 gallons of rain water per year! Which is closing in on 10-fold more than our current storage capacity -- we would have to empty and refill all four of our tanks ten times a year in order to capture all that we can. While I don't think we should consider our current system to be a shortfall, it does give one pause to think just how much precipitation falls upon such a relatively tiny roof in Concord and could be harnessed for landscape and garden watering. And why should we care, anyway?
While fresh water could one of our most renewable resources, it is becoming increasingly scarce. Efficiency and management of water resources and is going to be one of the most important issues in the decades to come. Here is an article from MSNBC about this issue that's nearly two years old, yet still on-target today: Crisis feared as US water supplies dry up -- Government projects at least 36 states will face shortages within 5 years (http://www.msnbc.msn.com/id/21494919/). Establishing a rainwater collection infrastructure for our outdoor needs is an integral part of our experiment in sustainability.
