Water managers are beginning to consider adapting to climate change. Some—but not all—water management plans and infrastructure have long lead times and long design lives. Improved understanding of the “science” of climate change impacts in the water sector is important but is not in itself enough to enable efficient adaptation. This is because it will never be feasible to base decisions on just one future climate scenario, particularly for time horizons greater than a decade. This is partly a result of incomplete knowledge but largely because of inherent uncertainty in future emissions of GHGs. Therefore, water managers always will be dealing with a range of scenarios, and research aimed at enabling efficient adaptation consequently must focus largely on appropriate analytical and management tools to cope with uncertainty and change rather than on “improving” climate change science and scenarios per se. In some aspects of water management—particularly associated with water quality—scientific research into processes is fundamental to allowing efficient adaptation.

Efficient adaptation to climate change in the water sector requires effort in five main areas:

• Data for monitoring. Adaptive water management requires reliable data on which to make decisions, calibrate models, and develop projections for the future. These data should cover not just hydrological characteristics but also indicators of water use.
• Understanding patterns of variability. An understanding of patterns of variability—in particular, the stability of a “baseline” climate—is important for medium-term water management. It is increasingly recognized that even in the absence of climate change, the recent past may not be a reliable guide to the hydrological resource base of the near future.
• Analytical tools. Effective water management requires numerous tools to assess options and the future. These tools include scenario analysis and risk analysis, which are used in some parts of water management but currently are by no means widespread.
• Decision tools. Scenario and risk analysis provides information on possible futures and their consequences. They must be supplemented with tools such as Bayesian and other decisionmaking tools to make decisions on the basis of the information provided. Again, techniques for decisionmaking under uncertainty are not widely used in water management at present, and some of the approaches being used are not very sophisticated.
• Management techniques. These are the techniques that are actually implemented to meet management objectives. The broad spectrum of techniques (such as building a reservoir or managing demand) is well known, but there is a need for research into specific aspects of many demand-side approaches in particular, as well as into opportunities for seasonal flow forecasting and innovative water supply and treatment technologies (such as desalination). It also is necessary to undertake research to determine how to enhance the range of techniques considered by water managers.

Note that the above efforts are needed to improve water management even in the absence of climate change, and there is an overarching need to improve the exchange of information between hydrological science and water managers.

Water managers have long been accustomed to dealing with change, although until recently this has been primarily change resulting from changes in demand and altered legislative or statutory requirements. Climate change does not in itself stimulate development of new adaptive strategies, but it encourages a more adaptive, incremental, risk-based approach to water management. More precisely, it provides further encouragement for a trend that already is gathering pace.

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