Assessing the Risks of Shifting Climate on Water and Power Operations in Reclamation Regions
How do we assess the risks of shifting climate on Reclamation operations? Many research groups are making future climate projections that vary by climate model choice and atmospheric composition scenario. This project involves surveying an ensemble of climate projections, analyzing ensemble impacts, and merging the uncertainty of both to quantify operational risk. This risk would then frame mitigation analyses on cost-efficient strategies for water supply development given future shifts in climate variability. The case study area is Mid-Pacific Region's Central Valley. The work-products would be (a) risk and mitigation information for MP, and (b) an assessment methodology that would be transferable Reclamation-wide. The methodology would describe how to relate climate projection ensembles to hydrologic/weather inputs in planning models, thereby enabling Area and Regional offices to conduct similar risk analyses but with their own planning tools.
Need and Benefit
On the subject of shifting climate variability and implications for long-term water resources planning, this work is about extending Reclamation's analysis perspective from "assessing impacts" to "assessing risk." Impacts assessment involves analyzing effects of a given scenario. Impacts magnitudes might be compelling, but decision-makers are likely going to ask about the probability before enacting a response. Without probability information, response is difficult. In contrast, risk assessment involves joint consideration of an ensemble of scenarios, their occurrence probabilities, and their impacts, and consolidating such information into a risk profile that describes range of potential impact and estimated probability. Such information enables statements of what will likely happen rather than what extremes could happen.
Reclamation has experience doing impacts assessment (e.g., projects funded in the 1990s by the U.S. Global Change Research Program). However, there has been no internal demonstration of (a) applying risk assessment principles for the subject of shifting climate variability and its potential effects on Reclamation service capabilities, or (b) working with climate researchers to establish criteria for sampling climate projection scenarios from the many that are available.
Completing this work requires a team with multiple skills and focus areas, including climate prediction, physical systems modeling, and operations modeling. Reclamation has internal capability to do physical and operations modeling, but not climate projection or sampling available projections. External guidance from climate research groups is required on the latter, particularly on sampling desirable projections (i.e. those that have been peer-reviewed and are referenced in international assessments on climate projections (e.g., IPCC Third Assessment Report of 2001 (IPCC3), IPCC Fourth Assessment Report scheduled for 2007 (IPCC4)). Climate researchers would also be called upon to assist the translation of global climate model outputs (i.e. region-scale atmospheric conditions) into basin-scale weather conditions that drive physical and operational impacts modeling (i.e. "downscaling").
Given that some of the skill requirements are beyond Reclamation's internal expertise, the proposed work involves collaboration between Reclamation, California Department of Water Resources (CA DWR), and climate researchers from USGS/Scripps Institute of Oceanography (USGS) and Santa Clara University. CA DWR is involved due to their joint interest in the project (see Section X.) and due to their ability to share work load on impacts modeling for the case study area.
The work begins with selecting scenarios from the climate projections database at the Lawrence Livermore National Laboratory's Program for Coupled Model Diagnosis and Intercomparison (LLNL PCMDI). The collaborating climate researchers would adopt and implement criteria to steer this selection, quantify climate change uncertainty (i.e. climate projections' distribution function, or CPDF), and translate the uncertainty to regional- and basin-scale shifts in climatological precipitation and air temperature. Reclamation would then work with CA DWR to analyze how basin-scale weather shifts influence physical and managed conditions in the Central Valley (e.g., rainfall-runoff, state and federal reservoir operations, aquatic temperatures in the Sacramento River system, and water quality conditions in the Sacramento-San Joaquin River Delta). This analysis would produce an ensemble of scenario-specific impacts for a variety of metrics (e.g., annual water deliveries, end-of-September storage, summer stream temperatures). The impacts ensembles would then be consolidated with the CPDF to produce a risk profile for each metric, which becomes baseline information for subsequent mitigation studies, also to be jointly completed by Reclamation and CA DWR.
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