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