California Drought Update - Mike Anderson, California State Climatologist, California Department of Water Resources

CA Drought Update 2015

US Drought Monitor Forum

April 16, 2015

Oroville Reservoir January 2009

Presentation Overview

• Current Drought Conditions

• Variability

Folsom Reservoir January 2014

California’s topographyaffects our weather and climate

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Annual Average Temperature (deg F)

1895-2000 21st Century POR Average

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Source: NOAA Climate Division 2 Calendar Year Data

2014

It’s Getting Warmer

2013

2012

April –July Runoff (million acre-feet)

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21st Century Droughts on the Sacramento River

1976

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20th Century 21st Century POR Average

5 of 20 lowest April-July flows since 2001

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Annual Average Temperature (deg F)

1895-2000 21st Century POR Average

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Source: NOAA Climate Division 5 Calendar Year Data

2014

2013

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It’s Getting Warmer

2012

April –July Runoff (million acre-feet)

Wat

er Y

ear

Ru

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ff (

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ion

acr

e-fe

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21st Century Droughts on the San Joaquin River

1976

25 of 20 lowest April-July flows since 2001

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1901-2000 2001-2014 POR Average

Worst April 1 Snowpacks2015 5 percent2014 25 1977 251988 291976 37

2007 392013 421963 451990 45

1994 522012 52

Year to Year Precipitation Variability

Dettinger et al, 2011

Std Dev of Annual PrecipitationMean Annual Precipitation

California precipitation is uniquely variable

Higher values are higher variability

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1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

Los Angeles County Sonoma Mendocino 8 Station Index 5 Station Index

Decadal Scale Variability

Comparison of WSI - Sacramento

Water Year Type 1924-1938 21st Century

W 2 2

AN 1 2

BN 3 3

D 4 5

C 5 3

Includes forecast of critical for 2015

Comparison of Runoff – Sacramento

21st Century Oct-Mar Apr-Jul WY

Max 18.06 13.09 32.09

Average 8.66 6.08 15.48

Min 4.29 2.6 7.47

1923-1940 Oct-Mar Apr-Jul WY

Max 17.96 12.93 31.83

Average 7.63 5.87 14.13

Min 3.27 1.94 5.74

Units are Million Acre-Feet

* From tree rings

18.6

8.7*

12.011.2

9.8

13.112.4

6.7

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WYAverage

1578-1580 1918-1920 1924-1926 1929-1934 1947-1950 1959-1961 1976-1977 1987-1992 2007-2009 2012-2014

SACRAMENTO FOUR RIVER RUNOFF

COMPARISON WITH PREVIOUS DROUGHTS

Average Annual Drought Period Runoff in Million Acre-Feet

Comparison of WSI - San Joaquin

Water Year Type 1924-1938 21st Century

W 2 3

AN 4 1

BN 2 2

D 2 4

C 5 5

Includes forecast of critical for 2015

Comparison of Runoff – San Joaquin

21st Century Oct-Mar Apr-Jul WY

Max 3.68 7.37 10.99

Average 1.55 3.41 5.08

Min 0.46 1.21 1.72

1924-1938 Oct-Mar Apr-Jul WY

Max 3.58 7.33 11.24

Average 1.33 3.38 4.80

Min 0.45 1.03 1.5

Units are Million Acre-Feet

* From tree rings

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2.3*

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WYAverage

1653-1655 1918-1920 1924-1926 1929-1934 1947-1950 1959-1961 1976-1977 1987-1992 2007-2009 2012-2014

SAN JOAQUIN FOUR RIVER RUNOFF

COMPARISON WITH PREVIOUS DROUGHTSAverage Annual Drought Period Runoff in Million Acre-Feet

Storm Track changes

Flooding &

water supply

MJO/Tropical

Convection ENSO

Polar Processes

Key Phenomena Affecting California Water Supply/Flooding:

Easterly Wave

Cyclogensis

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The size of the AR results from the

alignment of key processes

The absence of AR activity important to drought

Summarizing Thoughts

• 21st century droughts have shown record setting characteristics and are warmer than 20th century counterparts

• Atmospheric river events provide significant inputs into annual precipitation totals – fewer such events in drought years

Conclusions

• The expectation of increased variability means new extremes and extreme transitions with past few years serving as an example.

• Planning for future droughts can take advantage of information in the historical record including paleo reconstructions. The trick will be to increase our understanding of causal mechanisms and watershed condition/response.

Questions?

Email: [email protected]