Each summer, we rediscover the inverse relationship between rainfall and our water bills: when the rain stops coming down, water use — and the bill for it — goes way up. Robbin Pearce, water conservation analyst for the city of Ashland, says watering our landscaping accounts for a whopping 40 percent of summer water consumption. With shrinking water supplies and changing climate conditions, conserving water any way we can makes good sense.
Harvesting rainwater is an age-old concept involving collecting and storing water runoff. Typically, collection comes from roofs and is stored for future use. One of the most common, and easiest, uses of rainwater is for supplemental watering in the garden. Using a rain barrel is the simplest way to collect and store that water.
According to Pearce, lots of good things happen when rain is collected. First and foremost "it reduces demand on the municipal water supply," she says. "It also significantly aids stormwater management by reducing flooding, erosion and pollution caused by runoff." Depending on how much is collected and stored, it may reduce your water bill as well. Naturally soft and chemical-free, rainwater is good for your plants.
Collection is determined by the size of the collection area, your storage capacity and the amount of rainfall. According to Dylan Coleman, owner of Wonderwater Rainwater Catchment Systems in Mt. Shasta, "for every 1000 square feet of catchment [roof] surface, you can collect 600 gallons of water for every inch of rainfall." Translated for the Rogue Valley, that means with 1200 square feet of roof you could potentially capture around 12,200 gallons of water every year—more than you might want to store.
Rainfall from July through September is rare in the valley, but it only takes a single quarter-inch rainstorm to create enough runoff from an average size roof to fill a typical 55 gallon barrel. With that, you can fill your watering can 18 times. Keep in mind that rain barrels aren't for you if you have treated your cedar shake roof with fire retardant or added a fungicide to composition shingle roofs. Remember, water from these types of roofs is fine for plants, but not for drinking water.
Does it help conserve water? "Yes," says Pearce. "Even small amounts of supplemental watering can help reduce demands on domestic water supply." Coupled with other water-saving practices like mulching, drip irrigating and drought-tolerant plants, rainwater collection "can make a difference," says Pearce.
"Preassembled barrels, with hose fittings, overflow and mosquito/debris screening are widely available," says Dieter Trost of Southern Oregon Nursery in Medford. Do-it-yourselfers can purchase food grade plastic drums and plumbing fittings. You can find resources and DIY assembly instructions online.
With a little bit of planning this fall, you can gather and store rainwater, help conserve a precious resource, improve plant health and maybe even save some money, too.