Alan F. HamletAndrew W. Wood

Dennis P. Lettenmaier

JISAO Center for Science in the Earth System Climate Impacts Group

and Department of Civil and Environmental EngineeringUniversity of Washington

November, 2003

Observed Climate and Streamflow Variability in the Sacramento, San Joaquin, and Colorado

River Basins and Projections for the 21st Century

Observed Trends in Basin Average Temperature and Precipitation in the

Sacramento and San Joaquin River Basins (Water Year 1916-1997)

Note: Data is adjusted for topographic variations, and corrections for spurious trends associated with heat island effects, station moves, instrumentation changes, different groupings of stations, etc. have been applied.

Winter (O-M)

y = 0.0094x + 5.47672

3

4

5

6

7

8

9

1916

1920

1924

1928

1932

1936

1940

1944

1948

1952

1956

1960

1964

1968

1972

1976

1980

1984

1988

1992

1996

Tem

per

atu

re (

C)

Summer (A-S)

y = 0.0097x + 15.65813

14

15

16

17

18

19

16

19

20

19

24

19

28

19

32

19

36

19

40

19

44

19

48

19

52

19

56

19

60

19

64

19

68

19

72

19

76

19

80

19

84

19

88

19

92

19

96

Tem

per

atu

re (

C)

Observed Temperature Trends over the Sacramento San Joaquin Basin 1916-1997

Winter (O-M)

y = 1.2532x + 506.560

200

400

600

800

1000

1200

19

16

19

21

19

26

19

31

19

36

19

41

19

46

19

51

19

56

19

61

19

66

19

71

19

76

19

81

19

86

19

91

19

96

To

tal P

reci

pit

atio

n

(mm

)

Summer (A-S)

y = 0.1874x + 106.610

50

100

150

200

250

19

16

19

21

19

26

19

31

19

36

19

41

19

46

19

51

19

56

19

61

19

66

19

71

19

76

19

81

19

86

19

91

19

96

To

tal P

reci

pit

atio

n

(mm

)

Observed Precipitation Trends over the Sacramento San Joaquin Basin 1916-1997

Streamflow Reconstructions from the Paleoclimatic Record

Thanks to:

Hugo Hidalgo, Scripps Institution of OceanographyDave Meko, Laboratory of Tree-Ring Research, University of ArizonaConnie Woodhouse, Paleoclimatology Branch, NOAA National Climatic Data Center

Sacramento River Flow Reconstructed from Tree Rings

(6-year running mean)

Source: Meko et. al, 2001, J. Amer. Water Res. Association, 37(4) 1029-39 (Fig 5)

Sacramento and Upper Colorado Annual Flow Reconstructions

Concurrent periods of low flow are indicated by pink bands

Meko, D.M. and C.A. Woodhouse, in review. Tree-ring footprint of joint hydrologic drought in Sacramento and Upper Colorado river basins, western USA. Journal of Hydrology

Overview of Streamflow Reconstructions for Water Managers:http://www.ncdc.noaa.gov/paleo/streamflow/study.html

Sacramento River Reconstructions:Meko, D.M., Therrell, M.D., Baisan, C.H., and Hughes, M.K., 2001, Sacramento River flow reconstructed to A.D. 869 from tree rings: J. of the American Water Resources Association, v. 37, no. 4, p. 1029-1040.

Meko, D.M. and C.A. Woodhouse, in review. Tree-ring footprint of joint hydrologic drought in Sacramento and Upper Colorado river basins, western USA. Journal of Hydrology

Colorado River Reconstructions:Water Resources Bulletin, 31(5) (Special Issue on climate variability and drought in the Colorado River Basin)

Stockton, C.W. and Jacoby Jr., G.C. 1976. Long-term surface-water supplyand streamflow trends in the Upper Colorado River Basin based on tree-ringanalysis. Lake Powell Research Project Bulletin 18, Institute of Geophysicsand Planetary Physics, University of California, Los Angeles.

Some Selected Results from the Accelerated Climate Prediction Initiative (ACPI)

Accelerated Climate Prediction Initiative (ACPI) – NCAR/DOE Parallel Climate Model (PCM) grid over western U.S.

A hydrologic simulation model and a reservoir operations model were run in each portion of the domain.

Both sensitivity and adaptive response capability were evaluated.

Bias Correction

from NCDC observations

from PCM historical runraw climate scenario

bias-corrected climate scenario

month mmonth m

Note: future scenario temperature trend (relative to control run) removed before, and replaced after, bias-correction step.

Downscaling

observed mean fields

(1/8-1/4 degree)

monthly PCManomaly (T42)

VIC-scale monthly simulation

interpolated to VIC scale

Reductions in Pacific Northwest Snowpack for PCM Scenarios(low sensitivity)

The Main Impact Pathway in the West:Loss of Snowpack.

Results for the Sacramento and San Joaquin Basins

Van Rheenen, N.T., A.W. Wood, R.N. Palmer and D.P. Lettenmaier, 2004, Potential Implications of PCM Climate Change Scenarios for Sacramento - San Joaquin River Basin Hydrology and Water Resources, Climatic Change (accepted)

PCM Business-as-Usual scenarios

California(Basin Average)

control (2000-2048)

historical (1950-99)

BAU 3-run average

PCM Business-as-Usual Scenarios

Snowpack ChangesCaliforniaApril 1 SWE

PCMBusiness-As-Usual

Mean MonthlyHydrographs

Shasta Reservoir Inflows

1 month 12 1 month 12

Lake Shasta Storage: 4552 taf

Sacramento River Basin

Trinity

Whiskeytown

Shasta

Oroville (SWP)

Folsom

Clear Creek

American River

Feather River

Trinity River

Sac

ram

ento

Riv

er

Dam

Power Plant

River

Transfer

Delta

Delta & San Joaquin R Basin

Dam

Power Plant

River/Canal

Transfer

Eastman, Hensley, & Millerton

New Don Pedro & McClure

Delta

New Hogan

Pardee & Camanche

Stanislaus River

Tuolumne & Merced Rivers

Delta Outflow

Mokelumne River

Calaveras River

San

Joaquin

River

Pardee/CamancheReservoir

Storage: 615 taf

New Melones ResStorage: 2420 tafDon Pedro/McClureStorage: 3055 taf

Millerton LakeStorage: 761 taf

Sacramento-San Joaquin Delta

Area: 1200 mi2

Delta

New Melones

San Luis

Central Valley Water Year Type Occurrence

0.0

0.1

0.2

0.3

0.4

0.5

0.6

Critically Dry Dry Below Normal Above Normal Wet

Water Year Type

Per

cen

t G

iven

WY

Typ

e

hist (1906-2000) 2020s 2050s 2090s

Storage Decreases• Sacramento

Range: 5 - 10 %Mean: 8 %

• San Joaquin Range: 7 - 14 %Mean: 11 %

Current Climate vs. Projected Climate

Current Climate vs. Projected Climate

Central Valley Hydropower Production

200000

400000

600000

800000

1000000

1200000

1400000

OctNov

Dec Jan

Feb Mar Apr

May Ju

nJu

lAug

Sep

Meg

awat

t-H

ou

rs

Ctrl mean

2000-2019

2020-2039

2040-2059

2060-2079

2080-2098

Hydropower Losses• Central Valley

Range: 3 - 18 %Mean: 9 %

• Sacramento System Range: 3 – 19 %Mean: 9%

• San Joaquin System Range: 16 – 63 %Mean: 28%

Results for Colorado River Basin

Christensen, N.S., Wood, A.W., Voisin, N., Lettenmaier, D.P. and R.N. Palmer, 2004, Effects of Climate Change on the Hydrology and Water Resources of the Colorado River Basin, Climatic Change, (accepted)

Period 1 2010-2039 Period 2 2040-2069 Period 3 2070-2098

hist. avg.

ctrl. avg.

PCM Projected Colorado R. Basin Termperature

hist. avg.

ctrl. avg.

PCM Projected Colorado R. Basin Precipitation

Period 1 2010-2039 Period 2 2040-2069 Period 3 2070-2098

Changes to Seasonal Hydrograph

Simulated Historic (1950-1999) Period 1 (2010-2039)Control (static 1995 climate) Period 2 (2040-2069)

Period 3 (2070-2098)

Deliveries to Central Arizona Project & Los Angeles Metro. Water District

1 BCM = 810,832 acre-ft

Conclusions and Comparative Analysis

• 1) California system operation is dominated by water supply (mostly ag), the reliability of which would be reduced significantly by a combination of seasonality shifts and reduced (annual) volumes. Partial mitigation by altered operations is possible, but complicated by flood issues.

• 2) Colorado system is sensitive primarily to annual streamflow volumes. Low runoff ratio makes the system highly sensitive to modest changes in precipitation (in winter, esp, in headwaters). Sensitivity to altered operations is modest, and mitigation possibilities by increased storage are nil (even if otherwise feasible).

• 3) These potential impacts highlight the need for contingency planning to cope with reductions in water supply and flexible demand management strategies for the future.