Book 2.indb - US Climate Change Science Program

The U.S. Climate Change Science ProgramChapter 3Figure 3.1. Interior Department analysis of regions in the West where water supply conflicts are likely to occur by2025 based on a combination of technical and other factors, including population trends and potential endangered species’needs for water. The red zones indicate areas where the conflicts are most likely to happen. See DOI Water 2025Status Report (U.S. Department of Interior, Bureau of Reclamation, 2005; http://www.usbr.gov/water2025/report.html)for details. Note: There is an underlying assumption of a statistically stationary climate.situation raises the politically charged issue ofwhether the allocation of around 90% of theregion’s water to agriculture is sustainable andconsistent with the course of regional development.Mexico is also expected to dry in the nearfuture, turning this feature of hydroclimaticchange into an international and cross-borderissue with potential impacts on migration andsocial stability. The U.S. Great Plains, wheredeep aquifers are being rapidly depleted, couldalso experience changes in water supply thataffect agricultural practices, grain exports,and biofuel production. Other normally wellwateredregions of the United States may alsoface water shortages caused by short-termdroughts when demand outstrips supply andaccess to new water supplies is severely limited(e.g., Atlanta, GA). Other regions of the UnitedStates, while perhaps not having to face aclimatic change-induced water shortage, mayalso have to make changes to infrastructure todeal with the erosion and flooding implicationsof increases in precipitation intensity.Increases in the frequency of droughts inresponse to climate change can in turn producefurther climate changes. For example, increaseddrought frequency may reduce forest growth,decreasing the sequestration of carbon in standingbiomass, and increasing its release from70