In my last post I wrote about rain barrels and my interest in them as a means of supplying water for my lawn. This is of particular interest to me now since Georgia has been in a severe drought since at least 2007, if not earlier. On October 20, 2007 Governor Sonny Purdue declared a state of emergency due to the drought. Our watering probably will continue to be restricted for some time. Collecting water in a rain barrel allows someone to maintain their lawn or garden without putting a strain on the local water supply.
But before making a rain barrel, I need to answer two questions: 1) how much water do I need to apply to my lawn? and 2) can I collect enough water to make a rain barrel worthwhile? My gardening resource, Month-by-Month Gardening in Georgia by Walter Reeves and Erica Glasener, recommends my lawn receive 1 inch of water per week during the growing season, from about April through August. Despite the drought, it does rain during the summer in Georgia, so I don’t have to apply all the water. But just how much does it rain? I obtained 2008 monthly rainfall for my area in northeast Georgia from the National Atmospheric and Oceanic Administration’s National Weather Service.
You’ll notice from the table that during a drought year like 2008, I would need to apply water throughout the growing season, about April through August. The most water I would need to apply, assuming a year like 2008, is 2.78 inches per month, or about 2/3 inch per week. But what size rain barrel do I need to hold a month’s worth of watering? This depends on the size of your lawn. My lawn is 1085 square feet. I’m estimating that at worst I will have to apply 2.78 inches, or 0.23 feet, of water. I calculate the amount, or volume, of water I need by multiplying the square feet of lawn (1085) by the feet of water I must apply (0.23). This gives me 249.55 cubic feet of water. But who measures water in cubic feet? I want to know how many gallons of water I need to be able to store in a rain barrel. To convert the amount, or volume, of water from cubic feet to gallons, I multiply the cubic feet of water (249.55) by 7.48. That comes out to about 1,867 gallons per month, or about 467 gallons per week. The typical rain barrel seen for sale or demonstrated in a workshop is about 55 gallons. To make a dent in the watering requirement of my small lawn during the worst months, I would need to buy at least one 225-gallon rain barrel. I’d buy two of these barrels if I wanted to be completely independent of the local utility for my outdoor watering needs.
Now that I know how many rain barrels I’d need to water my lawn, can I collect enough water from my roof? In the worst month of 2008 (June), a 2,500 square foot or larger house, including any garage or porch, would have been able to collect enough water for my lawn for the same month. If your house is smaller, not a problem. You may be able to store water from previous months. And most importantly, this isn’t an all-or-nothing deal. You just have to decide how much water saving is enough to justify the investment in a rain barrel.
There is one more issue to consider that I haven’t mentioned: application. I need water pressure so that it doesn’t take forever to water the lawn. I could simply elevate the rain barrels and hope gravity helps enough. But I prefer something a little more high tech: a pump. I can attach a pump such as the Wayne 1/2 HP Portable Pump to the spigot of the rain barrel. Then I can attach a hose directly to the pump for watering my lawn, or anything else. I’d have to plug in the pump with an outdoor extension cord whenever I need to use it. If I choose to use multiple rain barrels I can connect them with some PVC piping so I only have to buy one pump. Of course, if you just want to water some plants in your small garden, the pressure from gravity will likely suffice.
If your roof collects more water than you think you can use via a rain barrel, you may want to consider creating a rain garden. In an upcoming post I’ll briefly describe how to create a rain garden on your property and provide resources to help you get started.