Demands are outpacing supplies, water costs are rising sharply,and current uses are depleting or contaminating some valued resources.
Climate change has the potential to either aggravate or alleviate an area's water situation.
On balance, however, the impacts are likely to be adverse because the existing water infrastructure and uses are based on an area's past climate and hydrology. In this paper, Frederick outlines the possible impacts of climate on water supplies, including its implications for regional uncertainties, sea levels, and carbon dioxide effects. He starts by reviewing the most recent scientific assessment by the Intergovernmental Panel on Climate Change, which suggests that global warming will have a wide range of effects on water resources. He notes that one of the more likely impacts, however, is in areas such as the western United States where precipitation is largely in the form of winter snowfall and streamflow largely comes from spring and summer snowmelt. Gradual warming in areas like this would likely result in a distinct shift in the relative amounts of now and rain in the timing of snowmelt and runoff.