Assessing Reservoir Operations Risk Under Climate Change
Water systems are facing an increase in potential impacts due to climate change. In the southwest U.S. the potential changes include reduced snowpack and subsequent summer flow, increased winter flooding, and increased aridity. Typically, scenario-based approaches are used to study management plans and this study takes a closer look at risk-based approaches. With risk-based approaches, an ensemble of "what-if" scenarios are part of a wide range of variables like rate of warming and potential precipitation used for demonstrating an array of future climate possibilities. This method reveals impact magnitudes while also addressing decision-making attitudes toward risk. To get to these adaptive, risk-based plans this case study focuses on two things:
- Propose and demonstrate a risk assessment framework
- Apply the framework multiple times to reveal sensitivity of portrayed risk to analytical design
In California, several risk-assessment variables like temperature projections are fairly reliable while other risk-assessment variables like future precipitation projections are predominantly unknown. Situations like this require an ensemble of possible scenarios from which a management plan can be derived. As as research and advancement in projection uncertainty improve, risk-based frameworks like the one proposed in this case study can be transitioned for adaptive management support. The locations used for this case study were chosen for how they reflect the differences among these situational variables.
Methods, Tools, and Data
For a detailed explanation of the methods and data, please view the case study available online here.
Risk Assessment Framework: Four Primary Steps
- Recognize decision drivers in the planning context and choose applicable risk assessment metrics and projection period
- survey an ensemble of climate projections and define a variety of climate possibilities, and weight them within the planning context
- Analyze scenario-specific models on associated operations
- integrate results from the above steps to construct a model of probably distributions of impacts
Sensitivity of Risk to Analytical Design
- Assumptions about Future Flood Control Constraints: subjective analytical design versus the default (control) analytical design
- Estimation of scenario weights for overall impact
Discussion of Results
Results from this framework's application in Northern California are found to be consistent with prior studies with regard to notable impacts, some of which can be controlled through reservoir operations. As well, risk results are found to be sensitive to analytical design choices though the weighting of the situations is less crucial than thet control assumptions embedded in the analytical design. The framework can be applied to other settings where future research is aimed at allowing management plans to adapt based on climate change risks. More strategic approaches for selecting projection scenarios, and more effort spent revealing risk sensitivity to a broader variety of analytical design choices would improve the framework's application.
Brekke, D., Maurer, E., Anderson, J., Dettinger, M., Townsley, E., Harrison, A., Pruitt, T. (2009). Assessing reservoir operations risk under climate change. Water resources research, 45(4). http://onlinelibrary.wiley.com/wol1/doi/10.1029/2008WR006941/full