In her new book, City Nature, Retallick explains the rationale for water harvesting—and how she put it into practice. “Even in the best of times, water is scarce in the desert. But when it rains, oh, does it pour! This is especially true in the summer, when several inches can fall in just a few hours,” writes Retallick.

   

“That’s good news if you’re in a wilderness, where 50 percent of that rainwater soaks into the earth. What happens to the other half? Well, 40 percent of it evaporates and 10 percent becomes runoff. Now, let’s experience the same heavy rainstorm in a modern urban setting like Tucson. Sorry to say, but 30 percent of that rain evaporates, 55 percent becomes runoff that floods our streets and washes, and only 15 percent gets absorbed by the soil,” she explains. “What’s the solution? Water harvesting. The goal? To allow rainwater to slow down, spread and sink into the ground.”

   

Since Retallick purchased her central Tucson home in 2004, she has incorporated two types of water harvesting—passive and active—into her landscape.

   

Passive water harvesting is simply the act of sculpting the landscape to direct the water to where it should be (like plants) and away from where it shouldn’t be (like a home’s foundation). Retallick’s landscape incorporates three passive water harvesting features—basins, berms and drainage swales.

   

Collectively, these earthworks eliminate the need for landscape irrigation that’s connected to the municipal water supply, which is served by Tucson Water. According to Tucson Water, approximately 40 percent of water use in Tucson is outdoors. This includes residential uses like landscape irrigation and garden watering.

   

Retallick’s irrigation-free landscape also includes two active water harvesting features, a 1,500-gallon cistern that collects rainwater for use in the backyard vegetable garden, and a laundry-to-landscape greywater harvesting system that diverts wastewater from the washing machine to three fruit trees.

   

City Nature is illustrated with more than 60 of Retallick’s color photographs, which show the wide variety of plant life on her property, the birds she shares it with and her various do-it-herself projects—the most notable being a kinetic sculpture created from a recycled chandelier.

   

The book also includes a list of suggested resources that encompasses books, websites, organizations and businesses that can aid readers interested in desert gardening and landscaping, and in water conservation.