3.6.1 The context for adaptation
Adaptation to changing conditions in water availability and demand has always been at the core of water management. Historically, water management has concentrated on meeting the increasing demand for water. Except where land-use change occurs, it has conventionally been assumed that the natural resource base is constant. Traditionally, hydrological design rules have been based on the assumption of stationary hydrology, tantamount to the principle that the past is the key to the future. This assumption is no longer valid. The current procedures for designing water-related infrastructures therefore have to be revised. Otherwise, systems would be over- or under-designed, resulting in either excessive costs or poor performance.
Changing to meet altered conditions and new ways of managing water are autonomous adaptations which are not deliberately designed to adjust with climate change. Drought-related stresses, flood events, water quality problems, and growing water demands are creating the impetus for both infrastructure investment and institutional changes in many parts of the world (e.g., Wilhite, 2000; Faruqui et al., 2001; Giansante et al., 2002; Galaz, 2005). On the other hand, planned adaptations take climate change specifically into account. In doing so, water planners need to recognise that it is not possible to resolve all uncertainties, so it would not be wise to base decisions on only one, or a few, climate model scenarios. Rather, making use of probabilistic assessments of future hydrological changes may allow planners to better evaluate risks and response options (Tebaldi et al., 2004, 2005, 2006; Dettinger, 2005).
Integrated Water Resources Management should be an instrument to explore adaptation measures to climate change, but so far is in its infancy. Successful integrated water management strategies include, among others: capturing society's views, reshaping planning processes, coordinating land and water resources management, recognizing water quantity and quality linkages, conjunctive use of surface water and groundwater, protecting and restoring natural systems, and including consideration of climate change. In addition, integrated strategies explicitly address impediments to the flow of information. A fully integrated approach is not always needed but, rather, the appropriate scale for integration will depend on the extent to which it facilitates effective action in response to specific needs (Moench et al., 2003). In particular, an integrated approach to water management could help to resolve conflicts among competing water users. In several places in the western USA, water managers and various interest groups have been experimenting with methods to promote consensus-based decision making. These efforts include local watershed initiatives and state-led or federally-sponsored efforts to incorporate stakeholder involvement in planning processes (e.g., US Department of the Interior, 2005). Such initiatives can facilitate negotiations among competing interests to achieve mutually satisfactory problem-solving that considers a wide range of factors. In the case of large watersheds, such as the Colorado River Basin, these factors cross several time- and space-scales (Table 3.4).
Lately, some initiatives such as the Dialogue on Water and Climate (DWC) (see Box 3.2) have been launched in order to raise awareness of climate change adaptation in the water sector. The main conclusion out of the DWC initiative is that the dialogue model provides an important mechanism for developing adaptation strategies with stakeholders (Kabat and van Schaik, 2003).
The TAR drew a distinction between 'supply-side' and 'demand-side' adaptation options, which are applicable to a range of systems. Table 3.5 summarises some adaptation options for water resources, designed to ensure supplies during average and drought conditions.
Each option, whether supply-side or demand-side, has a range of advantages and disadvantages, and the relative benefits of different options depend on local circumstances. In general terms,
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