My local government has a program to reimburse 100% of the cost of residential rain barrels, and since it’s hard for me to ever argue with “free,” I signed up. The only requirements are that each participant attend a lecture about rain barrels and related subjects (which I did), and that each participant also show a government inspector that they’ve properly installed your rain barrel (which I haven’t yet).
The presentation was given by environmental people from local agencies and nonprofits, and they explained that the primary benefit of rain barrels was to reduce storm water runoff and the attendant problems with flash flooding and fish kills. Roads and driveways are covered in motor oil and other chemicals, and lawns and farms are covered in pesticides and fertilizers. When it rains heavily, these chemicals are washed into waterways all at once, which kills aquatic life and also makes the waterways unsafe for humans for days.
A rain barrel helps mitigate this problem by storing the water that falls onto your house’s roof. You put the barrel next to your downspout and do some simple cutting and crimping of the metal downspout to connect it to a hole in the top of the barrel. During storms, the rain that falls on your roof flows into the rain barrel and stays there, reducing local water runoff by some minuscule amount. Presumably, if every house and building had a rain barrel, there would be a meaningful reduction in flooding and fish kills (the presenters unfortunately had no estimates, so I made some of my own below).
Before the presentation ended, the problem with the rain barrel concept became clear to me: they require routine maintenance. It’s up to homeowners to keep track of how full their rain barrels are and to periodically drain them (productive uses like washing cars or watering gardens were suggested), or else they’ll fill to the brim after a few storms and thereafter overflow each time it rains, defeating their purpose. Homeowners also have to check on them to make sure they aren’t clogged up with dead leaves or full of mosquito larvae.
Call me a cynic, but I think even this small amount of diligence is too much for most people, and rain barrels will function best if they automatically empty themselves of water. The simplest (and probably best) solution might be to screw a cap with a tiny hole in the middle over the rain barrel’s faucet. The hole would only allow a few drops of water to leak through it per minute, which would be a much slower flow rate than the unobstructed downspout. The rain barrel would fill during storms and then slowly discharge its load over several days. Keep in mind that it’s not the amount of rain that causes the problem, but the suddenness of the rain, so discharging all the water in your rain barrel won’t contribute to flooding or fish kills if it happens very gradually. Once-yearly maintenance might consist of cleaning the dead leaves out of the barrel and installing a new cap, which might cost $2.00 at Home Depot. That sounds doable for average people.
I’m going to call this idea the “Russian engineering solution.”
In lieu of making a cap, I’ve screwed a 4′ long extension hose into the spigot, and pointed the hose away from my house to prevent discharged water from flowing towards its foundations. Last Saturday night, my area got its first major rainfall since I installed the barrel, and to my surprise, it filled to the brim in a few hours (FYI, 700 square feet of roof feed into the downspout that is connected to the rain barrel). I opened the spigot and emptied out the tank on Sunday. However, it didn’t rain for the rest of that day or the next, and it occurred to me that the rain barrel’s utility as a storm water runoff and flood control device would be optimized if its discharges took rainfall forecasts into account and were timed to occur when the ground was as dry as possible.
In other words, because it rained on Saturday night, the ground was still soaked on Sunday, its absorbency was reduced, and the water I discharged from my barrel that day might have added to the runoff problem. It would have been better if I had instead drained the barrel on Monday since the ground would have been more absorbent thanks to the extra day of drying out, but I didn’t know that since I didn’t check the weather forecast.
Checking weather forecasts to time the barrel discharges requires unrealistic diligence from people, so automation would be necessary. And if we’re designing a truly “smart” rain barrel, why not try to full optimize it by programming it to consider all pertinent variables? This includes:
- The amount of water in the barrel (easily done with a float)
- Absorbency of the soil (estimated based on recent rainfall and barrel discharges)
- Rainfall forecast for the next 72 hours (including amount and timing of rainfalls; would require wireless access to an internet weather service)
- Conversion factor that uses the rainfall forecast to predict how much new water will flow into the barrel (the barrel could formulate its own conversion factor by comparing past rainfall events with corresponding increases to its own load)
And of course, the smart rain barrel would need internal features that would let it discharge itself without human help, and I think copying the tried-and-true toilet tank setup would be fine. A chain could connect the float to some type of simple machine, and the float’s rise and fall along with the water level would apply tension to the chain, which the machine would somehow store as potential energy (a mousetrap or a revolver’s hammer give clues as to how this can be done). When signaled by the smart rain barrel’s computer, the machine would use that stored potential energy to mechanically lift the “toilet flapper” at the bottom of the barrel, letting the water flow out.
I’m going to call this the “American engineering solution.”
Ha ha! So which do we prefer?
- Russian engineering solution: Simple, cheap, non-optimal but good enough
- American engineering solution: Complex, expensive, optimal
Call me unpatriotic, but I’m inclined towards the former. Glory to Russia!
And lastly, how much would rain barrels of either sort help mitigate storm water runoff and flash flooding? It’s impossible to say for sure, but this should be the starting point of any estimate:
‘In the United States alone, pavements and other impervious surfaces cover more than 43,000 square miles—an area nearly the size of Ohio—according to research published in the 15 June 2004 issue of Eos, the newsletter of the American Geophysical Union. Bruce Ferguson, director of the University of Georgia School of Environmental Design and author of the 2005 book Porous Pavements, says that a quarter of a million U.S. acres are either paved or repaved every year. Impervious surfaces can be concrete or asphalt, they can be roofs or parking lots, but they all have at least one thing in common—water runs off of them, not through them. And with that runoff comes a host of problems.
…According to the nonprofit Center for Watershed Protection, as much as 65% of the total impervious cover over America’s landscape consists of streets, parking lots, and driveways—what center staff refer to as “habitat for cars.”’ SOURCE
That means in the U.S., 35% of impervious surfaces are roofs of buildings or houses. If we make the very optimistic assumptions that 1) every roofed structure in the country had a smart rain barrel system, 2) the gutters and downspouts of each structure shunted 100% of the rain falling on their roofs to the barrels, and 3) the barrels were big enough to never overfill except during extreme instances like hurricanes, then the smart rain barrels would presumably reduce the runoff problem by 35%, which is nothing to sneeze at.
Of course, all of that assumes 100% participation rates and 100% efficiency rates, neither of which is realistic unless we’re thinking about the distant future, when humanity is much better off and has worked its way very far down the “Global Problems List.”
More realistic assumptions would set at everything at 50%: 50% of structures have rain barrels, the average rain barrel collects 50% of the rain that falls on the roof (that’s true of my own setup), the average rain barrel doesn’t overfill during 50% of rain events. In that case, the storm water runoff reduction is only 4.375%. [Frownie face.]
Well…I still got the damn thing for free!!!