Over the years, The University of Arizona has jettisoned some of its grass lawns in favor of desert landscaping. While this has cut down on the amount of water the UA has used on campus plant life, its created another landscaping problem in its wake.
One example is Fourth Street, which travels through the southern end of campus from Highland to Park. When it rains, water coming off the roofs and through downspouts of the buildings lining Fourth Street erodes the sand and gravel, washing some of it onto the sidewalks and into the street.
Except on a small patch of ground between the sidewalk and the Family and Consumer Sciences building, where piles of rocks and earth have been contoured to catch and retain rainwater. The design catches runoff and irrigate the plants there instead of flooding the street.
This bit of landscaping is the product of hydrologist Jim Riley, an associate professor of soil, water and environmental sciences, and the students who have taken his rainwater harvesting class.
Riley, whose office sits on the third floor of the Family and Consumer Sciences building, said several years ago a student came to him saying that there was money for students to work on water harvesting on campus, but that there should be an education component to the project.
Riley said if the project was funded, he would teach the class. It was, and this coming spring semester will be the fourth time he has taught it. With the help of UA Facilities Management, Riley and his students have slowly begun to transform one piece of the campus landscape. As other parts of the campus are added, the impact could be considerable.
"We did a study (funded by the Environmental Protection Agency) of 20 one-square-mile sections in Tucson and estimated how much rain falls on those areas," he said. "Then we asked Tucson Water how much potable water they deliver there."
What Riley found, to his surprise, was that the amount of rainfall equaled about three-fourths of the potable water that the city of Tucson was bringing in.
"I was expecting about 10 percent," he said. "This is a significant amount of water, even here. The thought that ‘We live in the desert and it doesn't rain much and when it does it doesn't amount to much, and when it does, it just runs down the street so we're not wasting much in the way of resources.' Well, it turns out that it does.
"The point is that water harvesting shouldn't be thought of as conservation. It should be another source of water, along with the ground water aquifers, the Central Arizona Project and reclaimed water."
Riley's classroom project is an example of passive water harvesting. The new additions to the College of Architecture and Landscape Architecture and the College of Optical Sciences incorporate passive water harvesting features as well.
So does the UA Visitor Center, which also has active water harvesting. Those are the large tanks, or cisterns, that collect and store runoff from the center's roof for later use.
The class Riley teaches incorporates some manual labor in moving rocks and dirt, figuring out whether the design works, and then moving more rocks and dirt until it all works.
"It's a three-unit class, and some of the instruction is on the end of a shovel. Projects are part of the class," he said, and noting that he's been surprised by the interest and enthusiasm the students have shown.
"We use (Tucson author) Brad Lancaster's book at the text and have him lecture when he can. Brad says it's about how you see things. Little things that you've seen all your life that at first didn't seem to be anything wrong. The notion that water should run off the sidewalk and into the ground, and not the other way around."
"Water harvesting is amazing and people are becoming more aware. It's shaping the land to keep water from running into the street. What you want is to keep it on the property, help reduce flooding and improve the water use on your own property."