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Please see EPA's Climate Change site for current information on climate change and global warming. EPA no longer updates EPA's Global Warming Site, but is maintaining this archive for historical purposes. Thank you for visiting the archive of EPA's Global Warming Site.
Climate Change and the Boston Area Water Supply
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U.S. Environmental Protection Agency, May 1995
The water supply of the Boston Metropolitan Area is found to be highly sensitive to climatic changes that are within the range of changes that climate scientists believe could occur during the coming century. Hydrologic and water management analyses of plausible changes in climate suggest the potential for either substantial increases or decreases in the amount of water that can be reliably supplied. The uncertain consequences of climate change for future water supply in the Boston area exacerbates the problems of local water resource planning and water supply investment decisions.
Whether or not water supply to Boston will increase or decrease is uncertain largely because local precipitation could either increase or decrease as a consequence of global climate change. Simulations from models of the global climate system vary considerably in their projections of precipitation for the northeastern United States. For a doubling of carbon dioxide in the atmosphere, or an equivalent doubling of carbon dioxide and other greenhouse gases, projected changes in precipitation in the region in which Boston is located range from a 25 percent gain to a 10 percent loss. This study finds that precipitation changes of these magnitudes, coupled with changes in evapotranspiration, would result in changes in the amount of water that can be reliably supplied from local reservoirs that range from a loss of one-half to a gain of one-third.
Water supply changes of these magnitudes may have important implications for the need to develop new sources of water supply and the cost of water to water users. In the absence of climate change effects, modest investments to expand local water supply and/or conserve water use are expected to be sufficient to accommodate population and economic growth in the area over the next several decades. However, if climate change decreases water runoff into local reservoirs, more substantial investments may be needed. In one scenario, a decrease in annual precipitation of less than 2% is estimated to reduce stream flows by 15% and the reliable water supply by more than 20%, illustrating the high sensitivity of water supply in the area to climate change. The study finds that the region has a number of options available for replacing a water supply loss of this size. The capital costs of these options is estimated at $700 million. Alternatively, if climate change increases water runoff, the investments in water supply and conservation currently thought to be needed to accommodate future growth in demand may not be necessary.
Because future climate conditions and their effects on water runoff are uncertain, water management planning may need to emphasize maintaining flexibility and preserving options for expanding supply and conserving water. Studies such as this one of the Boston Metropolitan Area can be a useful first step to aide water planners in assessing potential needs under different scenarios and to identifying options for meeting those needs.
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