California Department of Water Resources Climate Change Water Management

Andrew Schwarz P.E.California Department of Water Resources

California’s Wild Precipitation Regime

California’s Wild Precipitation Regime

Monthly Average Runoff of Sacramento River System

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep

Ru

no

ff (m

illio

n a

cre

-ft)

Month

1906-1955

1956-2007

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep

Ru

no

ff (m

illio

n a

cre-f

t)

Month

1901-1955

1956-2007

Monthly Average Runoff in San Joaquin River System

Snowpack Changes

We had already lost 1.5 MAF (1.85 billion m3) of snowpack between 1950 and 2010

Sea water

Possible Approaches

Study: “Climate Change Characterization and Analysis in California Water Resources Planning Studies”

http://www.water.ca.gov/climatechange/docs/DWR_CCCStudy_FinalReport_Dec23.pdf

California Water Plan 2013 Approach

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Planning for an Uncertain FutureSeeking shared understanding of :

• The existing state (of water) in the regions• A range of multiple, plausible future

conditions• What the options are to manage current and

future conditions• The options that seem to make the most

sense to invest in, in different regions

CWP Uses the WEAP Model

Customized Representation of Central Valley

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CWP Planning Approach Designed for Long-term Decision-making

• The future is uncertain: no single prediction of the future is adequate for planning

• There is no silver bullet: there are many options and important tradeoffs among them

• Analysis can only inform policy decisions: Analysis supports deliberation over tradeoffs

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19 Climate Scenarios

• 12 Climate projections taken directly from GCMs

• 4 Ensemble projections representing extreme conditions

• 3 runs of historical sequence

Downscaled AOGCM climate sequences

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% MonthlyIFRs Not Met

Urban water supply reliability(%)

Agricultural water supply reliability (%)

Performance of “Current Approach”

LowerPerformance

36 ScenarioResults

CurrentApproach

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Urban water supply reliability(%)

Agricultural water supply reliability (%)

Analysis Identified andCharacterized Poor Outcomes

CurrentApproach

% MonthlyIFRs Not Met

“X” = Pooroutcomes(bad for 2 of 3metrics)

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Urban water supply reliability(%)

Agricultural water supply reliability (%)

Climate Trends Define “Hot and Dry” Vulnerable Scenario

CurrentApproach

% MonthlyIFRs Not Met

Poor outcomesdescribed by“Hot and Dry”scenario