America's Most Endangered Rivers - (Page 7) Global warming will cause more frequent and more intense droughts and floods, like this flood in 2007 on Washington’s Nisqually River. WHAT'S IN A NAME? buffering against droughts. Bleak though these predictions may be, there is hope. We have many strategies that can help healthy rivers and the communities that depend on them adapt to moderate levels of global warming — working with nature instead of against it. But we all must recognize that there is no adapting to more extreme scenarios. Protection of healthy watersheds, restoration of damaged rivers, and enhancement of water efficiency can contribute to making American communities resilient in the face of these increasingly volatile conditions. luted runoff. Already weakened by past damage to their rivers, many communities will have a harder time adapting to the following impacts brought on by global warming. Drought Warmer temperatures will increase evaporation, melt snowpack earlier, lower surface water levels and decrease recharge to aquifers. The frequency and intensity of droughts will increase as a result. Some areas will receive less precipitation, while others will see rainfall shift to winter and spring, leaving summer months drier. In river basins such as the Rogue and Colorado’s Cache la Poudre that originate in mountainous areas, snowpack acts as a natural reservoir that stores winter precipitation and releases it throughout the drier summer months when demand is highest. Warming temperatures will turn snow to rain and melt snowpack earlier in the season. As a result, many communities, especially in the western United States, will have less water in the dry sum- mer and early fall months. In the Southeast, the 2007 drought has already cost farmers hundreds of millions of dollars and closed power plants due to a lack of cooling water. These same shortages also threaten species and ecosystems that have evolved over thousands of years to depend upon historical cycles. Flooding While water shortages will affect some regions, excessive rainfall will plague others. More frequent and more powerful storms will increase flooding in many regions of the country. Some areas will experience both drought and flooding in the same year. Earlier snowmelt and higher winter and spring precipitation will make mountainous areas particularly likely to experience increased flooding. These floods will claim lives and destroy property, especially in communities built in floodplains. Although flooding has always been part of a healthy river system, these “extreme” floods will likely be destructive as opposed to restorative, harming fish and AN UNCERTAIN FUTURE Global warming will have many impacts on rivers, and these changes will in turn affect water supply, agriculture, recreation, power generation and numerous other spheres. Global warming will be most disruptive to communities that are already vulnerable because of dam construction, deforestation, sprawl, unsustainable water use, untreated wastewater and pol- Why global warming and not climate catastrophe? There are many alternatives, each effectively describing one part of the problem while neglecting another. Many scientists opt for "climate change" because it describes the wide range of shifts in the climate. Others use "global warming" to stress the dire nature of the problem and convey a sense of urgency. We have chosen to use "global warming" throughout this report. It is meant to encompass a wide range of shifts in the climate from altered rainfall patterns to prolonged droughts, not merely a rise in temperatures. A M E R I C A’ S M O S T E N DA N G E R E D R I V E R S T M : 2 0 0 8 E D I T I O N | W W W. A M E R I C A N R I V E R S . O R G 7 NATIONAL PARK SERVICE http://www.americanrivers.org
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