SURFACE TEMPERATURERECONSTRUCTIONSFOR THE LAST 2 ,000 YEARS
NATIONAL RESEARCH COUNCILOF THE NATIONAL ACADEMIES
Photograph: Nevada Tourism Media Relations
Tucson
Photograph: Chazz Lane
Central Arizona Project
Photograph: Ben Amstutz
Photograph: Ben Amstutz
Photograph: Michael Koukoullis
Water transfers in the American southwest
Courtesy Glen MacDonald
Colorado River Compact1922
18 MAFAverage river flow, 1906 to 1922
18 MAFAverage river flow, 1906 to 1922
allocated to 7 basin states
15 MAF
18 MAFAverage river flow, 1906 to 1922
allocated to 7 basin states
15 MAF
allocated to Mexico
1½ MAF
Observed discharge, Colorado River
Compact allocation (16.5 MAF)
Observed discharge, Colorado River
Compact allocation (16.5 MAF)
15 MAFAverage river flow, 1906 to 2005
15 MAFAverage river flow, 1906 to 2005
UNITED STATESArizonaCaliforniaColoradoNew MexicoNevadaUtahWyoming
MEXICOSonoraBaja California
Low reservoir
Photograph: Glen MacDonald
T H E W E S T, WAT E R A N D T H E C O L O R A D O R I V E R
Tree-ring display at elementary school
Photograph: Tom Swetnam
The history of precipitation and runoff in the Colorado Basin as indicated by tree-rings
Edmund ShulmanPh.D. Thesis Harvard University1944
water stress
reduced cell division
less cell expansion
reduced photosynthesisnarrow ring
INDIRECTRELATION
Source: Woodhouse et al., 2006
100%
0%
St. George and LuckmanJJA temperature
EXPLAINED VARIANCE
100%
0%
St. George and LuckmanJJA temperature
Woodhouse et al.Annual discharge
EXPLAINED VARIANCE
stream gauge
tree-ring estimate
Source: Woodhouse et al., 2006
Source: Woodhouse et al., 2006
M E G A D R O U G H Tintensity at least equivalent to modern multiyear droughts
duration longer than the several years to decade thereof
Seager et al., Journal of Climate, 2008
Average reconstructed annual flow for the period 1844–1848 was lower than the observed flow for 1999–2004.
“”Woodhouse et al., 2006
The long-term perspective provided by tree ring reconstructions points to looming conflict between water demand and supply in the upper Colorado River basin.
“”Woodhouse et al., 2006
Dave Meko University of Arizona
Source: Woodhouse et al., 2006
Relic tree, circa 323 BC Harmon Canyon, Utah
1,200 years of Colorado River discharge Meko et al., GRL, 2007
The tree-ring record shows that droughts lasting decades have routinely gripped western North America.
“Jonathan Overpeck and Bradley Udall
”
As western North America currently endures its worst drought since 1900, it is important to realize that this drought might be nothing compared to what is possible in the future if megadrought and even ho!er temperatures coincide.
Jonathan Overpeck and Bradley Udall
“”
Tree rings provided the central evidence that caused municipal water agencies to
“RETHINK OLD ASSUMPTIONS”
about worst-case scenarios for reservoir operations and re-evaluate the potential duration and geographic scope of severe drought.
READING FOR THURSDAYDavid Meko and Connie Woodhouse (2010), Application of streamflow reconstruction to water resources management. M.K. Hughes et al. (eds.), Dendroclimatology, Developments in Paleoenvironmental Research.
Please read the complete paper (eventually).
FOR NEXT CLASSRead sections 8.3.3 and 8.3.4
MID-TERMEXAM
They all laughed at me...but I'LL SHOW THEM! I'LL SHOW THEM ALL!! BWAHAHAHAAA!
“”
at least one day before asking questions about your exam.
PLEASE WAIT
QUESTION 4A common misconception is that dendrochronology involves just counting tree rings. Describe three situations that would lead simple ring counting to provide an inaccurate estimate of tree age.
LABUPDATE
Photograph: Calvin Farris
Photograph: Lane Johnston