California faces significant challenges in ensuring that its water resources successfully meet diverse needs across the state in the coming decades. Escalating needs due to population and economic growth, potentially increasing agricultural irrigation requirements, and growing desires to dedicate more water to the environment will put a strain on a system that is near or exceeds capacity. These challenges are exacerbated by potential declines in available water supply due to natural variability and climatic changes (California Department of Water Resources [DWR], 2009).

How these long-term changes will unfold and affect California’s water system is highly uncertain. It is unlikely that...

Traditionally, water agencies have estimated future system performance, such as reliability and cost, by using trends based on historical statistics of hydrology and best-estimate forecasts of other important factors, such as demand, regulatory conditions, and the likely increases in new supply from investments. Given increasing recognition that the past is no longer a good predictor of future climate and of the large uncertainty in most planning factors, many agencies have increasingly incorporated handcrafted paths, calledscenarios, into their analyses.

Scenario analyses typically consider only a small number of handcrafted paths for the future. But managers of complex water systems find...

This chapter outlines the basic analytical steps followed in the report, describes the experimental design that formed the basis for generating a larger number of scenarios, and summarizes the key assumptions underlying this limited analysis. Chapters Four and Five present the results.

Building on work performed for the CWP Update 2009, the analysis addressed some of the key questions that are to be answered for the CWP Update 2013, with a focus on the Central Valley. These questions follow the five steps of RDM depicted in Figure 2.1 in Chapter Two:

How would the region’s current management approach perform under...

In this chapter, we describe the proof-of-concept analysis of the vulnerability of the Central Valley’s current water management. These results illustrate the use of RDM in identifying and characterizing the conditions in which the current management baseline would perform poorly. In Chapter Five, we describe the results of our proof-of-concept analysis. They show how response packages for the Central Valley could reduce these vulnerabilities, and they highlight the key trade-offs that water managers would need to make among the different strategies. Results are presented as answers to the questions that the report was designed to address, as listed in Chapter...

Chapter Four analyzed how well the current management baseline approach would perform across a wide range of futures with respect to three reliability metrics and a summary metric. We found that hot and dry climate sequences were the primary future conditions under which the region is vulnerable. This chapter analyzes supply augmentation options and describes their potential for reducing vulnerabilities. It then describes the key trade-offs among the augmentation options in terms of reducing vulnerabilities and cost. It ends with a discussion of how the results could help decisionmakers select a response package based on expectations of facing the hot...

This proof-of-concept analysis has demonstrated how RDM might be applied to the CWP analysis of vulnerabilities and response packages. It shows how the WEAP Central Valley Model could be used to generate different scenarios of future conditions and how these results could be used to define those conditions that would lead to poor performance in the current management baseline. Next, we show how the implementation of response packages could reduce vulnerabilities and lead to a more resilient system. Lastly, we show one example of how the trade-off between reductions in vulnerabilities and cost for the different response packages can be...