Rainwater Harvesting in North Carolina...

a couple of years ago I had the opportunity to work with the North Carolina General Assembly to design a rainwater collection system at the NC Legislative Building which takes stormwater runoff from the roof areas (about 100,000 square feet) and use this water to irrigate the plants that are on the grounds, inside and on the roof of the building, where the NC House and Senate meet.
With all of the discussion about the drought we were in, and expect to happen again, I don’t think that we give enough thought to how much water falls on our roofs...
During a 1 inch rainfall (barely enough to wash out a good golf game) more than 60,000 gallons of water flow off the roof of the Legislative Building. Capturing that water not only reduces the amount of water used by the building - it also takes that water out of the already over-taxed Raleigh stormwater system. On top of that, 80% of the cost of water is connected to it’s embodied energy. So rainwater collection doesn’t only conserve water, it also saves energy! How about that.
Granted, Raleigh has a lot of impervious surface, and the Legislative Building is not going to solve the City’s water problems alone, but I think it’s a really important message that the legislators have sent to the community: that water conservation is a huge deal, and we can do something to conserve water. If you want to see a video about the system installed at the Legislative Building, here’s the link:
http://www.ncga.state.nc.us/ncgainfo/cistern/raincatcher.html
It’s not too long, maybe 10 minutes or so.
On a smaller scale, rainbarrels are a great idea for collecting rainwater off of your roof. That water, amazingly, is probably almost as clean as your tap water. The math is the same as the bigger project, just with smaller numbers - a typical suburban house has a “footprint” of about 1,200-1,500 square feet. 1 inch of rain will get you about 600-750 gallons of usable water. In our area, that gets you 30,000 to 35,000 gallons of water each year (maybe a little bit less right now, since our rain levels are pretty low). Check your water bill... not bad, eh?
One of the problems with the economics of rainwater collection is that water rates in many parts of the country are so low, that it makes the simple payback take a long time. Just wait a few years. Globally, water scarcity is and always will be a bigger issue than oil (don’t get me started on oil). When oil runs out in 10-25 years (depending on whether you listen to the pessimists or the optimists) what’s going to happen? Well, you find another source of energy. There’s solar, wind, hydro, nuke, etc. What happens when we run out of water? Hmmm. Only 3% of the World’s water is fresh water. Of that, 78% is trapped in polar ice caps. That leaves less than 0.3% of the Earth’s water that is suitable for consumption.
When water becomes scarce, prices will go way up. Hopefully it won’t take such drastic conditions to get people to start conserving.
We’ll see.
More later...