Rainy Days and Rainwater Harvesting

On rainy days like today, my thoughts go to rainwater harvesting. A roof will collect around a gallon of water per square foot of area during a one inch rainstorm. The metro Boston area receives 40 to 55 inches of rain annually, with around 30 to 40 inches occurring during the catchment time of year (spring to fall). For a 1.97 inch rainfall event on a 900 square foot (30x30 residential home) roof, catchment could be calculated as follows. 900 x 0.5 gallons/in. rain/sq. ft. = 886 gallons/4 downspouts= around 221 gallons available to store per downspout. Over a season, each gutter might produce up to 4400 gallons to store. Pictured to the right is a traditional rain box set up in a 3 box combination with offset diverter and gravel bed with steel edging. Each rain box can hold 75 gallons, or 225 gallons per 3 box set up.
-Lauren Greenhow, General Manager, GreenHow, Inc.
www.GreenHow.com. Effective Organic & Low Impact Solutions, Lawn Care, Pest Control & Termite Control in Newton and Metro Boston.