Are the Pieces in Place for a Perfect Drought? Are the Pieces in Place for a Perfect Drought? Insights from the Past and Prospects for the Insights from the Past and Prospects for the Future Future Glen M. MacDonald Glen M. MacDonald Department of Geography Department of Geography UCLA UCLA www.biogeographer.com www.biogeographer.com Southern California Water Dialogue Southern California Water Dialogue July 2007 July 2007
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Are the Pieces in Place for a Perfect Drought? Insights from the Past and Prospects for the Future
Are the Pieces in Place for a Perfect Drought? Insights from the Past and Prospects for the Future. Southern California Water Dialogue July 2007. Glen M. MacDonald Department of Geography UCLA www.biogeographer.com. Los Angeles Times July 2007. - PowerPoint PPT Presentation
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Are the Pieces in Place for a Perfect Drought? Insights from Are the Pieces in Place for a Perfect Drought? Insights from the Past and Prospects for the Futurethe Past and Prospects for the Future
Glen M. MacDonaldGlen M. MacDonaldDepartment of GeographyDepartment of Geography
Southern California Water Dialogue Southern California Water Dialogue July 2007July 2007
Los Angeles Times July 2007
MacDonald, G.M., Rian, S. and Hidalgo, H. 2005. Southern California and the perfect drought. Colorado Basin Climate, MacDonald, G.M., Rian, S. and Hidalgo, H. 2005. Southern California and the perfect drought. Colorado Basin Climate, California Department of Water Resources, pp 50-57 (Map).California Department of Water Resources, pp 50-57 (Map).
‘‘Perfect Droughts’ Impact all of Southern Perfect Droughts’ Impact all of Southern California Water SourcesCalifornia Water Sources
MacDonald, G.M., Rian, S. and Hidalgo, H. MacDonald, G.M., Rian, S. and Hidalgo, H. 2005. Southern California and the perfect 2005. Southern California and the perfect drought. Colorado Basin Climate, California drought. Colorado Basin Climate, California Department of Water Resources, pp 50-57.Department of Water Resources, pp 50-57.
MacDonald, 2007, Quaternary InternationalMacDonald, 2007, Quaternary International
Depressed E Tropical and NE Pacific SST’s and prolonged droughts in California and Colorado Bsin during Medieval Warm Period. (Mann et al. 2005; MacDonald and Case, 2005, MacDonald et al. in press)
Perfect Drought Periods (~60 years)
~AD 1012-1075~AD 1130-1192
Crowley 2000 Science, 289: 270-277.
Thank you -Thank you -
PERSPECTIVE FROM THE COLORADO RIVER AND THE SOUTHWEST
Connie A. Woodhouse Department of Geography and Regional
Development University of Arizona
Main Points
• The Colorado River, an important source of water for 7 US states and Mexico, is over-allocated, a situation exacerbated by growth and drought.
• Extended records of streamflow from tree rings place recent droughts in a 500-year context: 20th-21st c droughts are not unusual.
• A new longer reconstruction, 762-2005, offers a regional perspective on a period known for widespread drought: the most persistent Colorado River basin drought occurred in the 1100s.
• Understanding drought in the Colorado River basin: linked to El Nino/Southern Oscillation (ENSO), but other controls may be important also.
The Colorado River Compact, signed in 1922, was based a record of streamflow from a period of time with unusually high flows.
Over-allocation + increased demands + drought = stressed system
Tree-ring data extend the gage record back in time and allow the recent drought to be evaluated in a long-term context
Tree-Ring Reconstructed Colorado River Flow, 1490-1997
Lowest 5-yr mean in gage record, 2000-2004
Old And New Tree-Ring Networks Used To ProducePDSI Reconstructions For The North American Drought Atlas
Version 1 Tree-Ring Network Version 2 Tree-Ring Network
NW
SW
MX
<1/2 COVERAGE >2/3 COVERAGE
MCA aridity appears to be best expressed in the ‘SouthWest’ and Mexico where tropical Pacific SSTs have the strongest impact.
Palmer drought severity index (PDSI) (Dai et al. 1998)
Summer PDSI = JJA average (integrates winter-spring-summer)
Recent drought began in 1994 in Mexico
Most severe and sustained in Mexico
12 consecutive years in central Mexico (and not over)
Unmatched in the instrumental record
Intense warming over Mexico contributing to PDSI trend
Tree-ring reconstructed summer PDSI used to calculate Drought Area Index (DAI) for Mexico
Recent drought unprecedented in 500 years?
Predicted aridity trend already underway in Mexico?
Central Mexico
Mexico
0
100
200
300
400
500
600
1550 1600 1650 1700 1750 1800 1850 1900 1950 2000
Year
Prec
ipitat
ion (m
m)
-12 -8 -4
count / cc
0 1 2
Cal
yr
BP
clamsnail
Molluskabundance
vs. PDB
-8 -4 0
% organic
20 40
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
K I R M A N L A K E
d18O (clams)
LOI
8 12 16
= Late Holocene Drought Events (Stine 1990, 1994)
C:N Ratio(bulk sed.)
80 100120140-30 -20 1 2 3
vs. PDB
d13C (clams)
d13C(bulk sed.)
d15N(bulk sed.)
vs. PDBvs. PDB
0 4 8 12
Salinity(Diatoms)
Depth(Diatoms)
m mg/L
0 2 4
Pinus/ Artmemisia
Ratio
SS
T
6.0
7.0
8.0
9.0
10.0
11.0
12.0
13.0
14.00.001.00
2.003.00
4.005.00
6.007.00
8.009.00
10.0011.00
12.0013.00
14.0015.00
Northeastern Pacific SST
Depth (m)
0 4 8 12 16
Salinity (mg/L)
80 100 120 140 160
count / cc
0.0 0.5 1.0 1.5 2.0 2.5
Cal y
r BP
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
11000
snail (/cc) clam (/cc)
Molluskabundance
vs. PDB
-12-8-40
d13C vs PDBd18O vs PDB
% organic
0 20 40 60
K I R M A N L A K E
Diatom-inferreddepth model
d18O, d13C Diatom-inferredsalinity model
LOI
8 10 12 14 16 18 20
= Late Holocene Drought Events (Stine 1990, 1994)
C:N Ratio
DroughtDrought Depressed NE Pacific SST’s and Continuous drought in California during Holocene Warm Period ~8000 – 3000 years ago. MacDonald, Moser, Bloom, Potito, Porinchu, Kremenetski
PC1
PC2
• Two patterns of circulation appear to be associated with drought in the Colorado River basin over the past five centuries. • The first: El Nino/Southern Oscillation (ENSO)-related conditions in the Pacific Ocean
• The second suggests ENSO may not be the only control on drought in the Colorado River basin.