WHY THE PAST
MATTERS
how tree rings and environmental history help us make
better decisions about water, climate and the future

managing RESOURCES
managing RISKS

Observation

“ The hills look like sawdust, really, that colour.
I've never seen it where the grass didn't
turn green in the spring before.”
JERRY MURPHY
Elnora, Alberta
source: Globe and Mail, 1 July 2009

what’s the worst that can happen?

Colorado River
Photograph: Al_HikesAZ

Colorado River Compact
1922

Average river flow, 1906 to 1922
18 MAF

allocated to 7 basin states
15 MAF
Average river flow, 1906 to 1922
18 MAF

allocated to Mexico
1½ MAF
allocated to 7 basin states
15 MAF
Average river flow, 1906 to 1922
18 MAF

Water transfers in the American southwest
Courtesy Glen MacDonald

Observed discharge, Colorado River
Compact allocation (16.5 MAF)

Average river flow, 1906 to 2005
15 MAF

Average river flow, 1906 to 2005
15 MAF

Climate history of North America
Younger Demise of Laurentide
Dryas Ice Sheet
20 16 12 8 4 0
THOUSANDS OF
YEARS AGO
Final Drainage
of Lake Agassiz
LAST GLACIAL MODERN
MAXIMUM OBSERVATIONS

CLIMATE PROXIES
ice cores
tree rings
lake sediments
speleothems
corals

(It was like this when we found it)

Plains droughts
Red River floods
Decadal variability

D R O U G H T FROM TREE RINGS
“...and the falling raindrops ripple out into every tree ring.”
ROGER DEAKIN

Tree-ring display at elementary school
Photograph:Tom Swetnam

earlywood latewood
cessation of growth
Photograph: Kevin Anchukaitis

Colorado River
Photograph: Al_HikesAZ

water stress

water stress
reduced photosynthesis

water stress
reduced photosynthesis
less cell expansion

water stress
reduced photosynthesis
less cell expansion
reduced cell division

water stress
narrow ring reduced photosynthesis
less cell expansion
reduced cell division

“rethink old assumptions”
CHARLIE ESTER
SALT RIVER PROJECT

Photo: NASA’s Earth Observatory

Renewable water resources, by country
Brazil
Russia
Canada
USA
China
India
Columbia
Peru
Zaire
0 2,000 4,000 6,000
Source: Shiklomanov and Rodda, 2003
km3/y

Cadillac, Saskatchewan, 1934
North Battleford, Saskatchewan, 1930
Photographs: National Archives of Canada

“ Drought severity over the Northern Plains
during 1932 – 1939 was likely triggered
”
instead by random atmospheric variability.
Hoerling et al., Geophysical Research Le ers, 2009

Martin-Philippe Girardin
Canadian Forest Service
Greg Pederson
United States Geological Survey
Glen MacDonald David Sauchyn Emma Watson
UCLA University of Regina Environment Canada
Erik Nielsen Jacques Tardif
Manitoba Geological Survey University of Winnipeg

Prairie tree-ring network
St. George et al., 2009

Red Deer
Calgary

North Saskatchewan River

Whirlpool Point
Alberta

Prairie tree-ring network
St. George et al., 2009

755 m 3/s
847 m 3/s
809 m 3/s
770 m 3/s
823 m 3/s
787 m 3/s
901 m 3/s
3

MEGADROUGHT
intensity at least equivalent to modern multiyear droughts
duration longer than the several years to decade thereof
Seager et al., Journal of Climate, 2008

1842 to 1876
Above average Below average
Source: St. George et al., 2009

g e o l o g i c a l
STRESS TESTS
for hydrological systems

“ This
must
be
voodoo.”
Anonymous
water manager

INDUSTRY PARTNER
Manitoba Hydro

St. George et al., accepted,The Holocene

TRACKING EXTR EM E FLOODS
“Winnipeg had a close call.”
INTERNATIONAL JOINT COMMISSION

AP Photo/U.S. Coast Guard, Lt. Brendan Evans

Winnipeg
population: 680,000
River diversion
Main channel
Photograph: Greg Brooks

have floods ever been worse?

Red River
Manitoba
Photograph: Greg Brooks

collecting
subfossil oaks 66
Photograph: Erik Nielsen

67
St.. George and Nielsen,The Holocene, 2003

“
The forts now stand like a castle of romance in the midst of
an ocean of deep contending currents, the water extending
for at least a mile behind them, and they are thereby only
approachable by boats and canoes.”
Francis Heron
Hudson Bay Company, 1826
St.. George and Rannie, Canadian Water Resources Journal, 2003

Flood damaged Normal growth
69
Photograph: Suzana Radivojevic

350 years of Red River floods
St. George and Nielsen,The Holocene, 2003

Winnipeg floodway
expansion 71

D E C A D A L CLIMATE VARIABILITY

‘Drought’ people get.
‘Decadal-scale climate variability’
gets me that glazed eye look.
JOHN FLECK
Albuquerque Journal

Pacific Decadal Oscillation index
3
2
1
0
-1
-2
-3
1900 1920 1940 1960 1980 2000

LOW
frequency

“
Decadal prediction, a new eld of study, focuses on time-
evolving regional climate conditions over the next 10–30 yr,
which is a time period of interest to infrastructure planners,
water resource managers, and others.
e decadal time scale offers a critical bridge for informing
adaptation strategies as climate varies and changes.
”
Meehl et al., BAMS, 2009
Photograph: Kman999

Decadal ‘hotspots’ in winter precipitation
0% 10% 20% 30% variance

Decadal variability synchronizes rainfall, streamflow and hazards in northern California
Ault and St. George, Journal of Climate, in press

Levee break, Sacramento River
Photograph: California Department of Water Resources

High D2M power in the ENSO-PDO ‘null’
Ault and St. George, Journal of Climate, in press

tree-ring records
Photograph: Neil Pederson

L E S S O N S F R O M THE PAST
“Study the past to divine the future.”
CONFUCIUS

managing RESOURCES
managing RISKS

WHY THE PAST
MATTERS
how tree rings and environmental history help us make
better decisions about water, climate and the future