Water is our most important resource, yet it is often taken for granted, particularly in economically developed regions with healthy watersheds. The easy availability of potable water from the tap belies the complexity and challenges inherent in the extensive network of pipes, treatment facilities, and storm drains that operate largely behind the scenes. “Except for periods when major investments are required, there really isn’t much need to understand how water travels in and out of our cities,” writes environmental engineer David Sedlak in Water 4.0: The Past, Present, and Future of the World’s Most Vital Resource (Yale University Press, 2014). “Unfortunately, it looks like we are approaching one of those periods.”

The recent public health crisis in Flint, Mich., affirms Sedlak’s warning. So far, high levels of lead have been found in the water supply of nearly 400 residences, and counting, along with dangerous amounts of lead in the blood of local children, The New York Times reports. A known neurotoxin, lead can cause serious and lifelong health problems. The independent, voluntary research team from Virginia Tech that is leading the tests has also detected bacteria in the water that cause Legionnaires’ disease. The research and subsequent media reports on the state of Flint’s water trend sociopolitical, as the situation was ultimately caused by the negligence and misconduct of the government agencies that cut corners on water-quality measures and scorned initial complaints from residents. (Although Flint has received significant attention, it's not the only municipality to have reported unsafe lead levels in its water over the past decade and a half.) But the catastrophe also raises the specter of a much larger threat in a system that is inherently designed to fail: a centralized water supply.

"The development of non-fracture critical water services would not only reduce the magnitude of a fouling-related disaster, like the one in Flint, but also ensure a more ecologically balanced approach and a reduction in energy consumption."

As Sedlak explains, centralized urban water systems throughout the world are now under significant stress from increasing population density, water-resource competition, changing precipitation patterns, and new sources of pollutants, such as endocrine-disrupting chemicals. Even without these pressures, centralized water is, by design, a fracture-critical system—one that is susceptible “to complete and sudden collapse should any part of it fail,” writes Thomas Fisher, Assoc. AIA, a professor at the University of Minnesota School of Architecture’s College of Design and director of its Metropolitan Design Center, in his book Designing to Avoid Disaster: The Nature of Fracture-Critical Design (Routledge, 2013). Fracture-critical design, Fisher continues, has four characteristics: a lack of redundancy, interconnectedness, efficiency, and sensitivity to exponential stress in the event of failure—all of which describe centralized water systems. “Perhaps the best long-term solution to our water problems will be to abandon centralized water systems altogether,” Sedlak says.

Recent proposals by the Victorian Eco-Innovation Lab (VEIL) at the University in Melbourne's Faculty of Architecture, Building, and Planning, in Australia, and the International Living Future Institute’s (ILFI’s) Cascadia Green Building Council (CGBC) call for the construction of decentralized water systems. The development of non-fracture critical water services would not only reduce the magnitude of a fouling-related disaster, like the one in Flint, but also ensure a more ecologically balanced approach and a reduction in energy consumption. The following three factors show how decentralized, net-zero water could positively impact infrastructure.

Contamination Risk
Decentralized systems are less vulnerable to contamination than are centralized systems. The fecal coliform bacteria detected in Flint’s water supply in 2014 became widely distributed, as did the added chlorine (to get rid of the bacteria) that corroded lead service pipes, thus polluting the entire network with large amounts of lead, according to The New York Times. Flint’s water services—a fracture-critical system—are inherently interconnected and susceptible to complete failure; according to a March 2011 CGBC report, “major catastrophe or malfunction of a big pipe system leaves its service population vulnerable to contamination or without access to potable water.” The ILFI’s Living Building Challenge offers what it calls a “soft path” approach to decentralizing water services based on small-scale, building-based water systems. The program’s list of criteria for projects to maintain water conservation—one “petal” in the latest iteration of the LBC program—challenges design teams to create independent water services based on captured precipitation or closed-loop systems. From a contamination standpoint, any polluting event would thus be limited to the scale of a building.

Resource Management
Decentralized systems also offer better means of managing an increasingly threatened resource. Water consumption has grown at a rate more than twice that of the world’s population in the past century, and water criticality is becoming a major global concern, according to the United Nations Department of Economic and Social Affairs. Not only are aquifers being depleted at an accelerated rate, but volatile precipitation patterns have made municipal water supply increasingly unpredictable. Furthermore, centralized water is typically accompanied by large infrastructure, such as dams and water treatment plants, that erode the resilience of complex watershed systems. The Living Building Challenge method avoids this heavy-handed approach to water services with its closed-loop approach. And VEIL researchers have proposed a distributed model through which production, distribution, and consumption systems are designed specifically to match local demand and resource availability. This model is composed of multiple, interdependent networks that operate at different scales—from the region to the neighborhood—and enhances the resilience of both centralized and decentralized services.

Energy Performance
Decentralized water also brings improved energy performance. A March 2002 study by the Electric Power Research Institute found that moving and treating potable and waste water comprise about 4 percent of U.S. electricity use. Roughly 85 percent of this electricity is consumed by pumps, Sedlak explains, for two primary reasons. First, many existing water systems operate against gravity, rather than working with it. Second, modern water systems must pressurize water in order for it to move through the underground network of pipes, and “… we often set the pressure for large sections of the system at values that assure that the minimum desired pressure will be experienced in the farthest faucet,” he writes. The decentralized approach is a much more energy-efficient option, as water is consumed close to the source and requires little or no pumping, particularly if gravity is employed judiciously.

"Architects should ... develop more expertise related to these net-zero water systems, as they will have direct implications for building design, construction, and operation."

There are, of course, impediments to decentralized water systems. Existing regulations are biased towards centralized systems, and public health codes typically demand connecting to public utilities. Cost is another barrier, either for a municipality that upgrades to distributed water services or for a building owner that faces the added cost burden of a water supply and treatment system. Decentralized systems are also viewed as unsafe, because they are not maintained by a central authority.

We may have no choice but to overcome these challenges. In many utilities today, “a significant amount of buried infrastructure—the underground pipes that make safe water available at the turn of a tap—is at or very near the end of its expected life span,” wrote the American Water Works Association in a 2001 report, suggesting the onset of a “replacement era” for infrastructure. Faced with an excessive price tag, municipalities may welcome decentralized water as the only feasible choice for future water delivery. Architects should therefore develop more expertise related to these net-zero water systems, as they will have direct implications for building design, construction, and operation.