Developing a Robust Planning Framework for Climate Change in California.

Project ID: 23027
Principal Investigator: Kevin Thielen
Research Topic: Water Operation Models and Decision Support Systems
Funded Fiscal Years: 2023 and 2024
Keywords: None

Research Question

This research aims to provide water resource planners tools to address the following questions:

1) Given practical constraints on some modelling efforts (time, funding, expertise), how can water resource planners identify and communicate key vulnerabilities of their system and examine the performance of operational alternatives in light of the uncertain impacts of climate change?

To address this question, this study will develop an analytical framework and visualization tools for incorporating DMDU practices in the CGB region. Specifically, this study will develop a tool to examine the interplay between system performance, as determined by model output, and key climate drivers (i.e. increasing temperatures, changing precipitation patterns). By applying elements of Robust Decisionmaking (Lempert, 2019), we can communicate system vulnerabilities across a broad range of potential hydrology which address performance metrics for a variety of sectors (e.g. hydropower, water supply, ecosystem benefits).

2) When needed, how can water resource planners best identify a smaller sub-set of climate scenarios to use in more detailed modelling efforts (e.g. economics, ecosystem impacts)?

Using the information from question 1, project managers may examine the system vulnerabilities to identify climate models representative of future system performance. This method is in contrast with methods that select climate change models based on GCM statistics which may not necessarily correspond to direct changes in system performance. For example, GCMs selected based on a range of variability in average annual precipitation or temperature do not necessarily capture the impacts of intra-annual variability which may have a stronger impact on flood risk.

Need and Benefit

The potential impacts of climate change on water resources are well established (Reclamation, 2021; DWR, 2020). A key difficulty for incorporating climate change information into the planning process is the ability to evaluate operational alternatives in a way that factors in the full uncertainty of future hydrology. A number of different approaches have been implemented to tackle this as discussed above. However, whether using stochastically generated hydrology as in DWR's Flood-MAR project, or GCM derived Climate Scenarios as in Reclamations ongoing study of the CVP/SWP system, planners often struggle to make decisions using the large amount of data generated. Some primary obstacles in this regard are as follows:

1. No potential future climate scenario is necessarily more likely than another.
2. Planning for a specific climate change scenario may reduce system performance under another, equally likely, climate change scenario. E.g. water supply operations considering futures with higher/lower annual inflows.
3. Decision-makers often need to select a limited number of climate change scenarios for use in more detailed modeling efforts (e.g. crop, economics, temperature for fish mortality). How can this subset of climate scenarios be selected to best represent future conditions?

To address these issues, recent studies have proposed the need to examine the "robustness" of system performance. I.e., treating all potential futures as equal, evaluate operational alternatives across all future climate, and all performance metrics (Brown, 2019). A "Robust" alternative is then one which satisfies all (or more than the other options) of the performance metrics, under the widest range of future hydrology. This framework also promotes study of the inverse, where no solution performs adequately one can then examine why, and begin to identify possible solutions. By communicating elements of robustness to decision makers and stakeholders, planning efforts are more capable of bridging the gap between climate uncertainty and operational planning.

Without this tool, water resource planners will continue to be limited in their ability to plan for uncertain future climate. Currently, planning efforts are hamstrung by their ability to prepare for future hydrological variability due to poor reliability in GCMs. This poor reliability is a primary obstacle in the current framework. The framework to be pursued in this study embraces this uncertainty in order to communicate meaningful conclusions.

Immediate benefits:
• Water resource planners will have a tool they can use for analyzing the system response to climate change across a broad range of uncertainty
• The reduced staff cost to conduct this analysis means a larger number of futures can be examined, and a more robust analysis of system vulnerabilities can be established.
• Improved analysis would allow for climate change impacts to be more readily incorporated into the planning process.
• Visualization tools will reduce time needed to prepare large data for communication to stakeholders.

This tool can be used as soon as it is developed by DWR for their watershed studies program and for Reclamation in CVP/SWP planning efforts.

Future benefits:

•Through the scenario discovery and vulnerability analysis components, the framework proposed will allow water planners to identify future scenarios where system performance may degrade and "sign-post" the hydrological changes which may cause that degradation.
•Such a planning tool will help socialize operationalization of climate change in reclamation leading to increased incorporation of climate change information in decision making.
•Reduced staff time needed for climate change analysis
•Increased impact of climate change analysis.
•Ability to identify potential for dynamic adaptation pathways into Reclamation projects via sign-posting.

Contributing Partners

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Research Products

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Last Updated: 6/22/20