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8 Freshwater Resources
Pages 257-270

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From page 257...
... This creates significant challenges for water resource management, especially where current water rights and consumption patterns were established under climate conditions different from the conditions projected for the future. Moreover, climate change is not the only problem putting demands on water supplies.
From page 258...
... SENSITIVITY OF FRESHWATER RESOURCES TO CLIMATE CHANGE Historically, the United States has relied heavily on surface water, and to a lesser extent groundwater, to meet its freshwater needs. It would be easy to assume that precipitation is the most critical factor in determining surface water availability, and thus future water supplies will be controlled almost entirely by changes in average annual precipitation.
From page 259...
... , and long-term strategic decisions need to be robust -- that is, able to meet water management goals under a range of plausible future climate conditions (e.g., Dessai and Hulme, 2007; Lempert, 2002; Lempert and Collins, 2007; Lempert et al., 2003)
From page 260...
... . Recent model projections indicate growing certainty that climate change could lead to increases in the strength of hurricanes, but how their overall frequency of occurrence might change is still an active area of research (Bender et al., 2010; Knutson et al., 2010)
From page 261...
... In the Southern Hemisphere, there has been no significant trend in South American snow cover, and data are sparse and inconclusive in Australia and New Zealand. In the United States, snowpack changes in the West currently represent the best-documented hydrological manifestation of climate change (e.g., Barnett et al., 2008; Pierce et al., 2008)
From page 262...
... . Elements of the Terrestrial Water Cycle: Surface and Groundwater Resources Analyses of stream flow records for the United States over the past several decades show primarily increases, which is consistent with trends in precipitation (Lins and Slack, 2005)
From page 263...
... Such challenges suggest that adaptive water management decisions will require regional climate information and may differ in their specific application from one river basin to another. Given the observed increases in heavy precipitation events and the expectation that this intensification will continue, assessments indicate that generally, the risk from floods will increase in the future.
From page 264...
... . Already, as climate change-driven impacts and other pressures on water resources unfold, water managers in drier regions of the United States find themselves confronted with the need to expand groundwater withdrawal and develop groundwater recharge schemes and infrastructure.
From page 265...
... . A surrogate indicator, derived from land-surface models, is the Palmer Drought Severity Index, which measures the duration and intensity of long-term drought-inducing patterns through thousands of data points such as rainfall, snowpack, stream flow, and other water supply indicators.1 The historical record of the Palmer Index from 1870 to 2002 shows that very dry areas have more than doubled globally since the 1970s, and the expansion after the 1980s is associated with surface warming (Dai et al., 2004)
From page 266...
... Integrated Water Resources Management often involves reforming broader institutional structures of water governance including decentralization, integration, participatory/collaborative management, and social learning. Adaptive management involves organizational and management processes that maintain flexibility (see Box 3.1)
From page 267...
... Likewise, projections of changes in the frequency and intensity of severe storms, floods, and droughts are critical both for water management planning and for adapting the natural and human systems that depend on water resources. This will require new multiscale modeling approaches, such as nesting cloud-resolving climate models into regional weather models and then coupling these models to land surface models that are capable of simulating the hydrologic cycle, vegetation, multiple soil layers, ground water, and stream flow.
From page 268...
... Reconciling water entitlements across different water systems, making water systems more flexible in the face of change, and shaping an institutional environment that encourages water conservation and reuse are only some of the challenges facing water resource institutions as climate change progresses. To improve our ability to design and deploy water institutions, more research is needed on governance mechanisms such as water markets, public-private partnerships, and community-based management.
From page 269...
... The role of ecosystems in recycling precipitation, influencing stream flow, and mitigating droughts is particularly important. Improving our understanding of the effects of water and land use on regional climate will be an important component of developing local and regional integrated climate change responses.


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