Basins, Swales and Sunken Gardens

Swales and basins are man-made depressions in the earth that slow the flow of storm water runoff so that it infiltrates the soil..  Swales are sometimes combined with curb cuts that allow water to run off of a roadway into depressions that are dug and planted along a sidewalk or in a median.  The collected water is used to grow plants that beautify the roadway, as well as for edible fruit trees.

Swales conbelow grade gardennected to curb cuts are not recommended for vegetable gardening, due to the high number of toxins that may be present in water that runs off of the street.  However, if your property is sloped, you may use swales and basins in a similar manner to catch and slow rainwater that runs down slopes or off of your roof for use in your garden.  If your property is flat, digging your garden bed below grade will form a basin that collects rainwater and sinks it into your garden bed.  It is also possible to direct roof run-off, greywater or air conditioning condensate to the basin to provide additional moisture.  Basins have the added benefit of holding deep mulch, which keeps the water in the soil by slowing evaporation.

The photos in this post are of a garden in Central Phoenix in June, one of the hottest and driest months of the year in Arizona.  Despite the arid desert conditions, the garden is lush and green.  To irrigate, gardener Craig uses a standard hose to fill the basins as needed.


sunken garden 2Learn more about water harvesting using man-made landforms:

City of Tucson Water Harvesting Guidance Manual

Rainwater Harvesting for Drylands and Beyond by Brad Lancaster

What is a Sunken Garden Bed:  Tips for Creating Sunken Gardens by Nikki Phipps, Gardening Know-How