James Laughlin, Managing Editor
Climate change and population growth could have a negative impact on water resources in the years ahead, both in terms of availability and water quality. I read two interesting articles on the topic recently -- one dealt with global warming and its impact on water supply, while the other discussed development of a Water Impact Index to assess the impact of human activity on water resources.
By mid-century, more than one-third of all counties in the lower 48 states will be at risk for water shortages as the result of global warming, based on estimates from a new report by Tetra Tech for the Natural Resources Defense Council (NRDC).
Demand was projected based upon a business-as-usual scenario of continued population growth and associated energy and cooling water needs. Supply -- or available precipitation -- was estimated from current and future temperature and precipitation scenarios, obtained from an ensemble of 16 global climate models. The analysis then compared future demand to future supply to provide an initial assessment of water resource sustainability across the nation.
The report’s authors projected that water withdrawals will grow by 25 percent in many areas of the US including the arid Arizona/New Mexico area, the populated areas in the South Atlantic region, Florida, the Mississippi River basin, and Washington, DC, and surrounding regions.
While estimated water withdrawal as a percentage of available precipitation is generally less than 5 percent for the majority of the Eastern United States, in some areas, such as Texas, the Southwest, and California, more water is already used than falls in the form of precipitation.
The Tetra Tech report includes a new water supply sustainability index that looks at projected water demand as a share of available precipitation; groundwater use as a share of projected available precipitation; susceptibility to drought; projected increase in freshwater withdrawals; and projected increase in summer water deficit.
A summary of the report and related links are available at www.nrdc.org/globalwarming/watersustainability.
The second article involved development of a Water Impact Index by Veolia Water North America working in cooperation with the City of Milwaukee and Milwaukee area water groups. The Water Impact Index expands on existing volume-based water measurement tools by incorporating multiple factors including consumption, resource stress and water quality.
It examines the impact of human activity on water resources and provides a methodology for establishing the positive and negative implications of how water resources are managed. The study is the first to take the balance of both carbon and water into consideration, and assigns a value to water based on quality, quantity and resource stress.
Veolia also announced what is believed to be the first-ever simultaneous analysis of water and carbon on a major metropolitan area’s water cycle.
The study confirmed the need to manage and locate future economic growth in areas that can sustain natural resources for future generations. It also reinforced the need to manage water and wastewater treatment systems through best practices that fully protect waterways but do so with cost efficiency and life-cycle costing that maximize value for citizens.
