Indicators of impacts of global climate change on U.S. water resources

Environmental and socioeconomic indicators are selected to study the impacts of global warming on the water resources of the United States. One of the indicators, regional storage vulnerability, is a particularly useful index summarizing the effectiveness of regional water supply systems to meet demands. A comparison of indicator tabulation and evaluation methods finds that reporting an indicator as a fraction of its stress threshold is most effective. Indicator display methods are compared, and the star diagram proves most effective as a visual aggregation technique. Indicators and evaluation methods are applied to the present climate and to one possible climate change scenario assuming economic growth. It is apparent that the primary impacts of global warming occur in the western U.S. and include (1) fewer relative stresses on hydroelectric systems due to an increase in energy supply from other sources, and (2) more stresses on available water resources due to increases in total withdrawals and, in some cases, decreases in flows. The writers believe that with wise indicator display methods, mathematical aggregation of indicators into indices may be unnecessary.