   Rain Gardens - May 28, 2014 Jeff Schalau, Agent, Agriculture & Natural Resources University of Arizona Cooperative Extension, Yavapai County In the past, I’ve written about rainwater harvesting which often uses a variety of techniques to keep water on-site for passive landscape irrigation or storage in tanks for subsequent use in the landscape. In high rainfall areas, their main benefit is passive treatment of stormwater runoff. In Arizona, rain gardens perform the stormwater treatment function in addition to passive rainwater harvesting that directs overland flow to planted depressions. As stormwater moves over impervious surfaces, it picks up and carries with it fertilizer, pesticides, pathogens, toxic contaminants, sediment and other pollutants before entering storm drains. These drains eventually lead to local waterways. Polluted runoff can harm aquatic life and make the waterways unsuitable for recreation and other uses. Studies along Oak Creek, which runs from Flagstaff, through Sedona, and flows into the Verde River near Cottonwood, have been detecting the bacterial contaminant Escherichia coli (shortened to E. coli) for many years. This is the reason for closure of Slide Rock State Park to swimming at times during the year. E. coli is commonly found in the lower intestine of warm-blooded organisms and, when detected in the environment, is correlated with fecal contamination. Studies in the Oak Creek watershed have detected E. coli originating from human, raccoon, skunk, elk, dogs and white-tail deer using genetic techniques which could differentiate between animal species. This work was done by agencies and universities in partnership with the Oak Creek Watershed Improvement Council. It provides an example of how rain gardens could mitigate localized pollution in our area and a reminder that harvested rainwater can contain pathogens and should be used with discretion on food crops. Many resources for rain gardens are available on-line and I have included links to these resources below. However, not many of these are developed for the arid west. Still, we can combine principles of rain gardens and passive rainwater harvesting for multiple benefits. In most residential settings, you will be trying to capture runoff from your house roof, driveway, sidewalks and other impervious surfaces and directing it to your rain garden. This can be accomplished by piping the downspout directly into your garden, or by letting it run over the land surface before entering the garden. When assessing your property for a potential rain garden, consider the following:
Follow the Backyard Gardener on Twitter – use the link on the BYG website. If you have other gardening questions, call the Master Gardener help line in the Camp Verde office at 928-554-8999 Ext. 3 or e-mail us at verdevalleymg@gmail.com and be sure to include your name, address and phone number. Find past Backyard Gardener columns or provide feedback at the Backyard Gardener web site: http://cals.arizona.edu/yavapai/anr/hort/byg/. Additional Resources Rain Gardens and Bioswales Utah State University Cooperative Extension extension.usu.edu/waterquality/htm/urbanstormwater/green-infrastructure/rain-gardens-and-bioswales Rain Gardens Rutgers New Jersey Agricultural Experiment Station water.rutgers.edu/Rain_Gardens/RGWebsite/raingardens.html Rain Gardens: Filtering and Recycling Rain Water Iowa State Cooperative Extension raingardensiowastate.pdf Note: plant lists from the eastern and midwestern states are not appropriate for the arid southwest. Use local Cooperative Extension resources to select plant materials for your area. Harvesting Rainwater for Landscape Use University of Arizona Cooperative Extension ag.arizona.edu/pubs/water/az1052/harvest.html  |