Climate and Managed Water Systems

Improving understanding of climate impacts on water resources

Decision and policy makers are increasingly faced with the need to understand the impact of climate change on water resources throughout the United States. With support from the National Science Foundation, the Bureau of Reclamation, the U.S. Army Corps of Engineers, and NOAA, NCAR scientists are working to understand fundamental hydrological processes under current and future climate conditions and to bring this state-of-the science understanding to bear on operational decision making and resource planning. This information, as well as new decision support technologies, will be increasingly important for state and local resource planning, wildland fire prevention and suppression, the agricultural and energy industries, forest and rangeland management, and agencies tasked with emergency response and public safety.

Figure 1. Decision Analytic Process used to helped water agencies consider climate change
Figure 1. Decision Analytic Process used to helped water agencies consider climate change
Figure 2. Process diagram for Palm Beach Count Water Decision Support Process
Figure 2. Process diagram for Palm Beach Count Water Decision Support Process

As water planners and managers become increasingly aware of global climate change and its possible impacts on water resources, they are seeking climate change information pertinent to their planning needs. To address these needs, RAL scientists, supported by the Water Research Foundation and NCAR's Assessment Program have developed climate change educational materials for the water resources community. Despite the pressing need, many water utility managers remain unsure if or how they should adapt to climate change. They correctly note that many uncertainties remain. In particular, reliable projections of local–scale changes in precipitation are not yet possible.

This uncertainty arises partly from fact that precipitation is inherently much more variable over time and space than is temperature. It also arises from the inability of coarse–resolution climate models to adequately simulate the fine–scale processes that determine where and when precipitation occurs. Statistical and dynamical downscaling techniques and higher–resolution climate models, made possible by more powerful computers, can help to increase the reliability of regional climate projections, but they won't eliminate all sources of uncertainty. In short, we know that climate change is likely to affect water resource availability and quality but we also know that we have a limited ability to foresee the full details of those changes, especially at local scales relevant to water planning.

Figure 3. A screen–shot showing the Upper Colorado, Platte, and Arkansas Basins within the Water Evaluation and Planning (WEA) decision support model
Figure 3. A screen–shot showing the Upper Colorado, Platte, and Arkansas Basins within the Water Evaluation and Planning (WEA) decision support model
Figure 4. Simplified Water–Energy Nexus
Figure 4. Simplified Water–Energy Nexus

Uncertainty is not a new phenomenon for water planners. Substantial uncertainties have long surrounded projections of future population growth, changes in water use habits, and construction costs. Uncertainty surrounding future climate projections is not fundamentally different from these more familiar uncertainties, except in degree and in the length of the time horizon. Effective planning can proceed, despite such uncertainties, by adopting a risk–management approach that considers a range of plausible projections for the most relevant, but uncertain variables.

Over the past few years, we have engaged with a select set of municipal water providers and related regional coordinating bodies in the development of a decision support process to facilitate assessments of water utility vulnerabilities and response options to prospective climate changes. These projects focused, in particular, on the problem of planning in the context of uncertainties surrounding the local–scale hydrologic changes that will result from global climate change. This has resulted in several reports, including Climate Change in Water Utility Planning: Decision Analytic Approaches. The projects have developed and demonstrated a structured assessment process to help the drinking water industry conduct scientifically sound and cost–effective assessments of utility vulnerabilities and adaptation options in the context of climate variability and change.

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Climate and Managed Water Systems