In this arid land, when it rains, it really does pour. Residents who hope to take advantage of this free, yet ephemeral water have begun a revival in the ancient practice of rainwater harvesting, which involves capturing and storing rainwater near where it falls. It’s no surprise that people are interested: harvesting rainwater can save energy and water, reduce the salt levels in the soil, and help reduce storm water runoff.

Rainwater harvesting involves slowing, spreading, and sinking the flow of water. Most residential yards grade away from the home, and this is still important to maintain. However, a few simple changes to the land can change the speed and path water takes when on its way out. When water moves slowly over the land, it has the opportunity to infiltrate, supporting plants and decreasing erosion.

Slowing this process can also reduce pollution from storm water runoff. When water flows quickly off a landscape, a higher volume hits paved surfaces like sidewalks and asphalt roads. Because water cannot sink into these surfaces, it runs off quickly, picking up sediments, debris, oil, and pet waste. The water eventually runs into storm drains that release directly into natural river sources, concentrating the pollutants.

Rainwater harvesting include installing both active and passive features. Active methods involve storing the water that falls off the roof in a tank or rain barrel. Ideal for watering vegetable gardens, these methods require actively re-using the water after storage. Passive water harvesting involves shaping the soil in the land to increase the infiltration of water, a process known as earthworks. Digging a basin, raising the soil to create a berm, or directing water with a gentle swale are all examples of the passive approach.

Both approaches must be used appropriately with best practices. Before installing active features, residents should consult with their city planning department to make sure that the proper permits are filed. Before digging in the soil, care must be taken to identify utility lines, such as gas and water. Arizona Blue Stake (602) 263-1100 can mark underground utilities for free.

Before aspiring harvesters pick up a shovel or purchase a rain barrel, the first step is observe the property, noting how water flows. The best systems support the overall landscape plan. For example, a homeowner may hope to plant a shade tree after observing that the west side of the home gets very hot. Rainwater harvesting features can be designed to best support the location of the potential shade tree. Simultaneously, the act of planting rain before the plant can guide the selection of a plant that would thrive in arid environments with infrequent, but deep rains.

When integrated into an overall landscape plan, rainwater harvesting can help reduce water use outdoors, encourage the health of plants and vegetation, and reduce storm water run-off. Successful harvesters start small and work from the highest points of the yard, carefully observing and enjoying the fruits of their labor.

Tina Sleeper is a Water Resource Specialist with the City of Phoenix, AZ, one of seventeen Water – Use It Wisely partners to offer water-saving advice and programs. Tina comes to the City of Phoenix by way of the University of Arizona’s Water Resources Research Center as Arizona Project WET’s Program and Community Coordinator.  She is also a volunteer and Phoenix Green Living Co-op member for the Watershed Management Group.  
 
 
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