Urban Water Crises
Urban water crises are not a thing of the distant future—they are happening all around us as long-term reductions in rainfall and runoff tie in with short-term multi-year droughts.
As one example, take the Atlanta region. The Metropolitan North Georgia Water Planning District (Metro), comprising 16 counties and more than 90 cities in and around the Atlanta area, delivers approximately 652 million gallons of water per day. Metro relies on surface water (streams, rivers, and lakes) for 98% of its water needs, with the Chattahoochee River Basin providing close to 70% of the district’s total water supply. The Atlanta region averages 50 inches of rainfall each year; however, the district periodically experiences times of extreme drought, such as in 2003 and 2007–2008. The impacts of drought periods for north Georgia are severe because the region does not import any water.
NO CLIMATE CHANGE EFFECTS
CLIMATE CHANGE EFFECTS
These maps from the Natural Resources Defense Council (www.nrdc.org
) show the predicted effects of climate change on water supply by mid-century. A 2010 study commissioned by NRDC found that 1,100 counties (one-third of all counties in the lower 48 states) will face higher risks of water shortages by 2050 as a result of global warming; more than 400 of those counties will face extremely high risks of shortages.
In September 2007, Georgia’s Environmental Protection Division (EPD) imposed Level 4 (the most severe) drought restrictions, banning most types of outdoor water use in northern Georgia. At that time, the Atlanta region had only about 30 days’ water supply left in storage. Metro’s main water source, the greatly depleted Lake Lanier, came to symbolize the seriousness of one of the worst droughts in the region’s history.
The Georgia EPD officially lifted drought watering restrictions in June 2009, 18 months later, after the second-wettest spring on record significantly replenished the region’s lakes and reservoirs. Upon announcing the end of the drought, EPD’s director stated, “The decision to ease outdoor watering restrictions should not be seen as a license to waste water, but as a vote of confidence in Georgians’ ability to conserve and use water efficiently.”
As the state transitioned from mandatory drought management to more voluntary water conservation, local and state water officials in Georgia planned to achieve sustained water conservation savings by continuing to foster positive water-use choices, including developing a “culture of conservation” in the region. In fact, Metro’s Water Supply and Water Conservation Management Plan predicted that, without aggressive ongoing water conservation, “water usage will reach the limits of projected available supply by 2030.” Through a series of Water Conservation Actions, Metro is expected to reduce average annual water demand by an estimated 20%, to satisfy the needs of a growing regional population and to guarantee reserve water supplies through 2030.
Urban water crises in the past five years have also affected such diverse places as San Antonio and Austin, Texas; Las Vegas; and San Diego, Los Angeles, and San Francisco. Clearly, we cannot let major cities fall victim to water insecurity if we are to have a healthy economy over the long term. Because of water supply shortages caused by climate change, we can expect planning for adequate urban and suburban water supplies to get even more difficult. There’s one more wrinkle, however: Water supply also takes energy, and energy supplies are also under pressure.
The Water/Energy Nexus
Water and energy are linked, now and forever, like conjoined twins. It takes electric power to move water from place to place, to pump it from rivers and groundwater, and to treat it before and after use. At the same time, it takes water to provide cooling for thermoelectric power plants (our major source of power), both fossil and nuclear, and, surprisingly to some, for concentrating solar power plants, today’s most cost-effective solar power system. Without a reliable energy supply, there can be no water supply; without a reliable water supply, there can be little energy production. This relationship is called the water/energy nexus.
There’s no magic bullet that will provide adequate energy supply for growing water demands and enough water supply for growing energy demands. What’s required is, first, a recognition of the connection and, second, a planning effort that considers future water and energy needs together, one that develops different approaches for different regions and relies heavily on conservation investments and integrated planning of water and energy infrastructure.
One of the leading experts on this issue is Mike Hightower, an engineer working at Sandia National Labs. In his view, “climate change will likely decrease our surface water supply capacity and, because of the over-pumping and drawdown of aquifers, the availability of groundwater supply is going to decrease. So, while we’re seeing an increasing demand for water for agriculture, people, and energy production, we’re also seeing freshwater supplies likely decreasing. So we’ve got water supply going in one direction with available supplies going down, and at the same time we have water demands going up. That’s not a good situation.”
One of the interesting, and non-intuitive, results of the water/energy nexus is that water conservation is by far the cheapest form of energy conservation, even more than insulation or higher-efficiency windows, for example. So by conserving water, builders and homeowners are also inadvertently contributing to energy conservation.
Many experts predict that, by mid-century, global climate change will cause significant problems for urban water management in the U.S., unless more water agencies begin to incorporate efficiency and reuse as integral parts of supply planning. We know that water supply, distribution, and treatment use significant amounts of energy—in California, for example, it’s more than 20% of all energy use. What I call “nega-gallons” (supply gains from conservation and efficiency programs) is by far the cheapest method to stretch our water supplies. While the water/energy nexus will continue to challenge planners, by recognizing their interaction, we’ll be able to make better decisions for the future.
You can expect building codes and local regulations to become more focused on water conservation in housing, with requirements for drip-irrigation systems, low-flow fixtures, low-water-use appliances, and dedicated plumbing for greywater. For example, Tucson, Ariz., now requires greywater stub-outs in all new homes. As the green building movement continues to gain traction, local governments will likely begin adopting such codes as the ASHRAE 189.1 standard, IAPMO’s Green Plumbing and Mechanical Code, or the ICC Green Construction Code, all of which mandate increased water conservation.
Home builders can play an important role by providing houses and developments that require less water. My research convinced me that it’s not that difficult to follow EPA’s WaterSense guidelines to reduce home water use by 20% indoors and up to 40% outdoors. The result: a home that lives more lightly on the planet and one with significantly lower water bills in the years ahead.
Two things are certain about water: It will be a subject of great interest in the coming decade and also a subject of great contention.
Jerry Yudelson is principal of Yudelson Associates in Tucson, Ariz., and a Professional Engineer. He is the author of Dry Run: Preventing the Next Urban Water Crisis (New Society Publishers, 2010) and 11 other books on green building.