IPCC Fourth Assessment Report: Climate Change 2007
Climate Change 2007: Working Group II: Impacts, Adaptation and Vulnerability

3.6.3 Adaptation options in practice

Since the TAR, a number of studies have explicitly examined adaptation in real water management systems. Some have sought to identify the need for adaptation in specific catchments or water-management systems, without explicitly considering what adaptation options would be feasible. For example, changes to flow regimes in California would “fundamentally alter California’s water rights system” (Hayhoe et al., 2004), the changing seasonal distribution of flows across much of the USA would mean that “additional investment may be required” (Hurd et al., 2004), changing streamflow regimes would “pose significant challenges” to the managers of the Columbia River (Mote et al., 2003), and an increased frequency of flooding in southern Quebec would mean that “important management decisions will have to be taken” (Roy et al., 2001).

A number of studies have explored the physical feasibility and effectiveness of specific adaptation options in specific circumstances. For example, improved seasonal forecasting was shown to offset the effects of climate change on hydropower generation from Folsom Lake, California (Yao and Georgakakos, 2001). In contrast, none of the adaptation options explored in the Columbia River basin in the USA continued to meet all current demands (Payne et al., 2004), and the balance between maintaining power production and maintaining instream flows for fish would have to be renegotiated. Similarly, a study of the Sacramento-San Joaquin basin, California, concluded that “maintaining status quo system performance in the future would not be possible”, without changes in demands or expectations (VanRheenen et al., 2004). A review of the implications of climate change for water management in California as a whole (Tanaka et al., 2006) concluded that California’s water supply system appears physically capable of adapting to significant changes in climate and population, but that adaptation would be costly, entail significant transfers of water among users, and require some adoption of new technologies. The feasibility of specific adaptation options varies with context: a study of water pricing in the Okanagan catchment in Canada, for example, showed differences in likely success between residential and agricultural areas (Shepherd et al., 2006).

Comprehensive studies into the feasibility of different adaptation options have been conducted in the Netherlands and the Rhine basin (Tol et al., 2003; Middelkoop et al., 2004). It was found that the ability to protect physically against flooding depends on geographical context (Tol et al., 2003). In some cases it is technically feasible to construct flood embankments; in others, high embankments already exist or geotechnical conditions make physical protection difficult. Radical flood management measures, such as the creation of a new flood overflow route for the River Rhine, able to reduce the physical flood risk to the Rhine delta in the Netherlands, would be extremely difficult politically to implement (Tol et al., 2003).