James Riley spoke to a standing room-only crowd about the importance of harvesting rainwater for Tucson. His talk was the focal point of the “”Science Café”” at Cushing Street Bar and Restaurant, 198 W. Cushing St., Tuesday night.

“”We need to think of water harvesting not just as water conservation, but to think of it as another source of water,”” the environmental science associate professor said.

Water harvesting is the process of diverting rainwater for storage to be used for irrigation or landscaping.

His talk was based on a city ordinance passed in October of last year mandating that commercial buildings meet at least 50 percent of their landscape water use through rainwater capture.

Riley said the UA Mall alone requires about five feet of rainwater per year to maintain its grassy greenness. He estimated that a 250-square-foot rooftop could capture approximately four feet of rain. This, combined with Tucson’s annual rainfall of one foot, would be enough to water the Mall.

Riley also discussed ways the UA is wasting water. The Manuel Pacheco Integrated Learning Center has a basement water tank that can hold 26,000 gallons of water, a necessary feature for an underground building. Once the tank is full, however, Riley said its contents are pumped directly to the surrounding streets.

The talk attracted an audience that consisted of Tucsonans, professors, sustainability professionals and students who asked questions ranging from the costs of installing a cistern – about $2-$4 dollars per gallon – to the level of toxins in roof runoff.

Students of Riley’s water harvesting workshops offered at the UA have been leading projects at and around campus with the aim of addressing water issues.

David Watson, a soil and water science senior and one of Riley’s pupils, is one of the students leading a project, and attended the discussion.

Watson is working with the Rincon Heights neighborhood to implement a community water harvesting plan, in response to the neighborhood not having a sewer system.

“”I feel I’m very much like a coach, as opposed to strictly a teacher,”” Riley said.

The results of Riley’s workshop can be seen at the UA Visitors Center, the south side of the Family and Consumer Sciences building and Cochise Hall. Lincoln Perino, a UA alumnus who works for the Tucson company Technicians for Sustainability, also took Riley’s workshop previously and attended the discussion to serve as an expert to address technical questions from the audience.

“”(Watson and I) are from Tucson so growing up here you kind of see the problems,”” Perino said.

Riley said it was important for anyone new to water harvesting to start small before tackling larger projects. A simple way to do that is by looking at where and how rainwater falls off of a roof.

“”Maybe go to Home Depot and buy a plastic trashcan,”” Riley said. “”See how much you can get from this.””

Susan Nares, a UA administrative assistant, left the talk inspired and looking to do more in terms of her own water harvesting.

“”I know Dr. Riley. I respect the fact that he has been working diligently on water harvesting on the U of A campus,”” Nares said. “”I myself do a little bit of water harvesting at home, but now that I’ve heard him speak I’m really excited about doing more things at home.””