Sea Surface Temperatures,
Drought, & Drought Prediction
in California
Ian Ferguson & John Dracup
Environmental Engineering Group
Dept. of Civil & Environmental Eng.
University of California Berkeley
Introduction:
Drought…
“I don’t get no respect…”
Rodney Dangerfield,
Actor/Comedian
“Droughts are the Rodney
Dangerfield of natural
disasters.”
Don Wilhite,
Director, National Drought
Mitigation Center
Introduction
Drought Impacts:
• Costliest of natural disasters
• $6-8 Billion/yr in US (FEMA 1995)
• Impacts all water users:
• Municipal • Agriculture
• Industrial • Recreation
• Environment
• Energy
(www.waterplan.water.ca.gov)
Introduction
Mechanisms of Hydroclimatic Variability:
• Significant difference
between precipitation,
temperature for El Nino
versus La Nina winters
• Significant relationships
also with PDO, AMO
(WRCC, Updated from Redmond and Koch 1991)
Introduction
Mechanisms of Hydroclimatic Variability:
• Strong, persistent SST
anomalies during periods
of widespread US drought
(Seager 2005)
Introduction
Mechanisms of Hydroclimatic Variability:
• AGCM reproduces much
of the observed low
frequency variability in
precipitation over US
Great Plains
• Exciting progress on
understanding key
mechanisms of severe,
sustained droughts!
(Schubert et al. 2004)
Introduction
That’s great!
…But how does this relate to
water resources management?
• Basin-scale drought events?
• Real world, real-time management decisions?
Outline
• Water supply & droughts in California
• SST & streamflow variability
• SST & drought events
• Implications for water management
• Future research direction…
Water Supply & Droughts in CA
California Water Supply:
• Largescale water systems:
• Multi-year reservoir
storage
• Nearly state-wide
conveyance network
• Primary water supplies:
• Sacramento River
• Colorado River
(Imports)
(Total Runoff = 15.2 maf)
(www.waterplan.water.ca.gov)
Water Supply & Droughts in CA
Sacramento River Basin:
• Mean flow: 22.4 MAF/yr
(31% of state’s annual runoff)
• Supplies more than 50% of the
water consumed in CA
Sacramento River Water Year Flow (Four River Index)
40
35
Annual Flow (MA
30
25
20
15
10
5
0
1905
1915
1925
1935
1945
1955
1965
1975
1985
1995
Year
(cdec.water.ca.gov)
(www.waterplan.water.ca.gov)
Water Supply & Droughts in CA
Colorado River Basin
• Mean Flow: 15.2 MAF/Yr
(CA receives 4.4 MAF)
• Primarily serves Southern
CA’s irrigated agriculture
Colorado River Water Year Flow at Lees Ferry, AZ
40
35
Annual Flow (MA
30
25
20
15
10
5
0
1905
1915
1925
1935
1945
1955
1965
1975
1985
1995
Year
(www.usbr.gov)
(www.waterplan.water.ca.gov)
Water Supply & Droughts in CA
Droughts in California:
Drought
Years btw Droughts
Duration in Years
1898-99
1912-13
1918-20
1922-24
1929-34
1947-50
1959-61
1975-77
1987-92
?
-13
5
2
5
13
9
14
10
at least 15
2
2
3
3
6
4
3
3
6
?
(www.waterplan.water.ca.gov)
Water Supply & Droughts in CA
Correlation Between Sacramento & Colorado:
Departures from Mean Water Year Streamflow
20
Colorado River
Sacramento River
DeparturefromMean(M
15
10
5
0
1905
1915
1925
1935
1945
1955
1965
-5
-10
-15
-20
Year
DWR-Defined Drought Events
Correlation: 0.469
1975
1985
1995
Outline
• Water supply & droughts in California
• SST & streamflow variability
• SST & drought events
• Implications for water management
• Future research direction…
SST & Streamflow Variability
Correlation with Preceding DJF SST Anomalies:
Sacramento River Annual Flow
Colorado River Annual Flow
S O N D J F M A M J J A S O N D J F M A M J J A S O N D
(Preceding DJF)
(Water Year)
SST & Streamflow Variability
Correlation with Preceding DJF SST Anomalies:
Sacramento River Annual Flow
Colorado River Annual Flow
S O N D J F M A M J J A S O N D J F M A M J J A S O N D
(Preceding DJF)
(Water Year)
Outline
• Water supply & droughts in California
• SST & streamflow variability
• SST & drought events
• Implications for water management
• Future research direction…
SST & Drought Events
Composite: Preceding DJF SST Anomalies
Sacramento River Annual Flow
Colorado River Annual Flow
S O N D J F M A M J J A S O N D J F M A M J J A S O N D
(Preceding DJF)
(Water Year)
SST & Drought Events
Composite: Preceding DJF SST Anomalies
Sacramento River Annual Flow
Colorado River Annual Flow
S O N D J F M A M J J A S O N D J F M A M J J A S O N D
(Preceding DJF)
(Water Year)
SST & Drought Events
Composite: Preceding DJF SST Anomalies
1976-1977 Droughts
1987-1992 Droughts
S O N D J F M A M J J A S O N D J F M A M J J A S O N D
(Preceding DJF)
(Water Year)
Outline
• Water supply & droughts in California
• SST & streamflow variability
• SST & drought events
• Implications for water management
• Future research direction…
Implications for Water Management
In Short:
• YES…
• 20th century streamflow in the Sacramento and
Colorado Rivers is significantly correlated with SST
anomalies over some ocean regions
• BUT…
• Composite analysis suggests that there is no
significant SST anomaly pattern during critical drought
events in the Sacramento and Colorado River basins
Implications for Water Management
Implications for Decision Makers:
• Poor prospects for long-lead
(statistical) streamflow
forecasts based only on SST
Outline
• Water supply & droughts in California
• SST & streamflow variability
• SST & drought events
• Implications for water management
• Future research direction…
Future Research
Future research direction:
• Consider primary streamflow processes in Sacramento
and upper Colorado River basins…
• Precipitation
• Snow accumulation & melt
• Evaporation, infiltration, & runoff
¾ How is each influenced by large-scale
atmospheric dynamics, and ultimately
ocean-atmosphere interactions?
Questions?