assessing impacts and responses, it is unlikely that sufficient resources will be available to do this comprehensively on an ongoing basis. One way to address the resource issues associated with assessment is to build a broad conceptual framework or matrix linked to smaller-scale illustrative examples. For example, an assessment could be conducted at a national level, accompanied by selected localized case studies of impacts on specific sectors or implications for specific local decision making. The work on the broad themes and trends can be an ongoing effort, while individual, integrated, local, or sectoral assessments can be nested strategically in the broader research agenda. This will help develop an ongoing assessment program that has more coherence over time.

An example of the application of the nested matrix approach is using global climate models to identify likely future changes in temperature and precipitation at the national and regional level that may result from climate change. By connecting such outputs to hydrologic models, it is possible to identify a range of likely impacts on runoff for specific watersheds and evaluate potential vulnerabilities for regions and sectors. Based on that information, specific regions or sectors that are identified as areas of high vulnerability can be selected for a more focused integrated assessment that includes the demographic and institutional context as well as physical parameters. At a regional scale, the vast amount of place-based information, including additional drivers (e.g., land-use change), can be incorporated into the analysis to provide a more comprehensive treatment of potential changes in water quality and quantity.

Recommendation: CCSP should consider implementing a nested matrix concept in developing subsequent assessments.

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