E A R T H - F R I E N D L Y   G A R D E N I N G

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Free Water for Your Garden

by Jo Miller, Water Conservation Coordinator, City of Glendale

The monsoon season is upon us, and with a little luck we will get some rain. Instead of letting rainwater run down the streets, you may want to consider harvesting it to help water your landscape. Rainwater harvesting involves taking action to preserve and use the rainwater on your property. Typically, rainwater is harvested in two ways:

By collecting and storing from gutters into containers such as barrels and tanks. (Make sure they are sealed or use mosquito dunks to control mosquitoes).

By encouraging water to soak in and be stored in the soil by constructing earthworks such as basins, depressions, berms, or on-contour trenches (called swales). Water should soak in within one day.

The following lists some of the many advantages of using rainwater in your landscape:

• Rainwater is better for most plants.
• Less rainwater is lost to evaporation if allowed to absorb in the soil. Deeper water penetration encourages worms and other organisms, making soil healthier.
• Rainwater increases the efficiency of drip systems through supplementation.
• Reduction of storm water runoff and non-point source pollution.
• Reduction of landscape erosion/flooding.
• Rainwater is free and does not strain community resources.

To assess your potential for harvesting water, it is helpful to spend some time outside observing what happens after a rain. In a one-inch rain event, the average house can shed well over 1000 gallons of water off the roof. Where is this water going? Drawing a map of your property will help you determine where you have the potential for collecting water on your property. Your map should include the following:

• Indicate with arrows the pitch of the roof and flow of water from the roof.
• Indicate the high and low point of your property.
• Make note of any areas where water flows on or near your property from an outside source.
• Mark any low spots where water tends to accumulate.
• Indicate the direction and approximate degree of slopes.

Once you have observed the flow of water on your property, you are ready to start with some simple harvesting techniques. Small earthworks such as berms or basins may be the easiest place to start.

Note: Water harvested from shingle, tar, or asphalt roofs is not recommended for use on edible plants.



Maricopa County Master Gardener Volunteer Information
Last Updated July 28, 2003
Author: Lucy K. Bradley, Extension Agent Urban Horticulture, University of Arizona Cooperative Extension, Maricopa County
© 1997 The University of Arizona, College of Agriculture and Life Sciences, Cooperative Extension in Maricopa County
Comments to Maricopa-hort@ag.arizona.edu 4341 E. Broadway Road, Phoenix, AZ 85040,
Voice: (602) 470-8086 ext. 301, Fax (602) 470-8092