In the United States, water use in buildings and their surrounding landscapes accounts for about 47 billion gallons per day, or 12 percent of our total water usage. Yet that is only a small piece of the story: fully half of the water we consume is used in the process of electric power generation, and our buildings and the gadgets housed in them are the principal consumers of electricity, with residential and commercial buildings together accounting for over 72 percent of total retail electricity sales in 2007, according to the U.S. Dept. of Energy.
At the same time that water is central to power generation, the California Energy Commission reports that extraction, treatment, conveyance, use (including heating), and disposal of water account for 20% of state electricity use and 30% of natural gas use. Water and energy are bound together, and bound with them are greenhouse gas emissions.
Then, there’s the question of where all that water ends up. As architect and water conservation advocate Geoffrey Holton wrote recently in arcCA (Architecture California), the journal of the American Institute of Architects, California Council (AIACC), “Surface runoff from streets, parking lots, and other impervious surfaces is often full of contaminants, which storm drains distribute into local groundwater, lakes, rivers, and tidal areas. Meanwhile, treated potable water . . . is used once, to flush waste or to wash, and sent immediately to overburdened sewage treatment systems.”
Which is tremendously costly: as David O’Donnell of Los Angeles based TreePeople observed in an earlier issue of arcCA, “One of the ironies of modern urban life is that municipalities spend millions of dollars each year to contain and dispose of stormwater, millions more to acquire the fresh water they need. The irony is especially pronounced in the American West, where scant rainfall can be nonetheless destructive and population centers are often far removed from adequate water supplies.”
In its recently completed Master Plan for the Sproul Student Community Center at UC Berkeley—recipient of the 2010 Honor Award for Urban Design from the AIACC. Moore Ruble Yudell Architects & Planners proposed an integrated system of water-conserving infrastructure. Green roofs will collect rainwater, which will then be stored in cisterns, for use in landscape irrigation, along with grey water from lavatories and drinking fountains. As Holton notes, “The use of grey water for irrigation does more than cut the use of potable water. By diverting water from the sanitary sewer to the landscape, it draws on the natural filtration capacity of root and soil systems, decreasing the burden on aging infrastructure and helping to replen¬ish groundwater, with associated benefits for local soil, plants, and wildlife.” Green roofs serve other functions as well, helping to insulate the building while reducing the “heat island effect”—the build-up of heat in large expanses of hard materials, like paving and conventional roofing.
Such multi-functional thinking is what architects are best at, imagining how an element that insulates can also conserve water, or how something that reduces solar heat gain can provide a comfortable gathering space sheltered from the rain, advertise a business, and complete a graceful visual composition (think “awning”).
The informed imagination of architects is also crucial for navigating the regulations that govern the reuse of water in buildings. Historically, hygiene, not water conservation, has been the driver of plumbing codes, which, until recently, have discouraged the use of grey water and captured rainwater. This situation is beginning to change, as sustainability in all its forms becomes central to the building regulatory process. But the learning curve can be steep.
Integrating water conservation into all our buildings and landscapes is essential to our future. Pauline Souza, AIA, of WRNS Studio, whose City of Watsonville Water Resources Center won a 2010 Top Ten Award from the AIA Committee on the Environment, sums up the situation well: “In a state like California, where climate change threatens to worsen droughts, growing populations compete with farms for water resources, and the aging infrastructure is having trouble keeping up, every drop counts.”