disentangling the inﬂuence of temperature and antecedent ... · temperature and antecedent soil...

Research partners: Adam Csank: Desert Research Ins�tute Steph McAfee: University of Nevada, Reno Greg Pederson: USGS-‐Bozeman Greg McCabe: USGS-‐Denver Steve Gray: USGS-‐Anchorage Water management partners: Bureau of Reclama�on, Lower Colorado District Colorado River District (State of CO) Denver Water, Colorado NOAA Colorado Basin River Forecast Center Salt River Project, Arizona

Disentangling the Influence of Temperature and Antecedent Soil Moisture on Colorado River Water Resources Project start and dura�on: September 1, 2014, 24 months Funder: U.S. Department of the Interior, Southwest DOI Climate Science Center

Purpose of the workshop: Year 1 assessment and Year 2 direc�ons for this project Plan for the Day (workshop agenda):

  Summary of results to date (instrumental data analysis)

  Work in progress (tree-‐ring reconstruc�ons)   Planning for future climate impacts analysis   Feedback, ques�ons, discussion, comments , sugges�ons throughout!

Introduc�ons

Disentangling the Influence of Temperature and Antecedent Soil Moisture on Colorado River Water Resources

PART 1: How have the contribu�ons of antecedent soil moisture, spring/summer temperatures, and total cool season precipita�on varied during the major periods of low flow in the upper Colorado River basin (UCRB)? And more generally, what have been their contribu�ons to water year flow?

Data   Gridded climate data from PRISM for total monthly precipita�on, average monthly temperature (4 km resolu�on)

  Monthly soil moisture storage from McCabe and Wolock (2011) monthly water balance model

  Water year natural flow es�mates for the Colorado River at Lees Ferry and major tributaries

  Analysis period: 1906-‐2012

  Data have been converted to percen�les in compara�ve analyses

Analysis Variables   October-‐April total precipita�on   March, March-‐May, March-‐July average temperature   October or November soil moisture

correla�ons

Selec�on of temperature, precipita�on, and soil moisture variables for analysis

Monthly mean temperature Monthly total precipita�on

Correla�ons with Colorado R Lees water year flow, 1906-‐2012 (prior July – September)

5 Oct-‐April total precipita�on April, March-‐Apr-‐May, and March-‐July

average temperature

*

correla�ons

Antecedent soil moisture assessment

Correla�ons of Lees Ferry water year flow with soil moisture storage and monthly flows for the common years, 1981-‐2010, prior October to September.

McCabe/Wolock water balance model soil moisture capacity

CBRFC model soil moisture storage

monthly Colorado River at Lees Ferry flows

McCabe/Wolock soil moisture was selected (longer dataset than CBRFC, higher correla�ons with flow than CBRFC and monthly flows) October and November selected, based in large part on our hypothesis of antecedent soil moisture influence

correla�on

Quan�fying the contribu�on of cool season precipita�on, temperature, and antecedent soil moisture in water year flow

Stepwise model with pool of 6 predictors:   Oct-‐Apr precipita�on   March, March-‐May, Mar-‐Jul temperature   Oct , Nov soil moisture

Step Multiple Multiple R-square F - to p-level Variables+in/-out R R-square change entr/rem included

OctAprP 1 0.813312 0.661476 0.661476 205.1700 0.000000 1MarJulT 2 0.859178 0.738188 0.076712 30.4723 0.000000 2novsoil 3 0.870644 0.758021 0.019834 8.4423 0.004488 3

March-‐July temperature accounts for only 8% of the total variance explained, but is it more important in certain years?

Colorado River at Lees Ferry, natural flows, 1906-‐2012

Major Droughts*

*using defini�on from Drought Catalog for Reclama�on -‐ below average flows broken by no more than 1 year of above average flow

Average values for each hydroclima�c variable across all years in a given drought period, color coded by drought

9

Individual years with in major droughts: percen�le values of WY flow, and variables that influence flow

1930s

1950s

2000s

Lees Ferry flow and October-‐April total precipita�on, in percen�les

Lees Ferry flow and October-‐April total precipita�on, in percen�les

Gray bar = 1 standard devia�on from the mean; these are years when Lees WY flow is markedly greater or less than Oct-‐Apr total precipita�on (ver�cal bars are individual years)

flow greater rela�ve to precip

flow less rela�ve to precip

Trend in March-‐July average temperature, 1906-‐2012

A closer look: 4 flavors of years

Colorado River flow

A closer look: 4 flavors of years

Colorado River flow

Water year flow and cool season precipita�on, averaged for each set of years

Years with flow < precipita�on above median flow yrs below median flows yrs

Years with flow > precipita�on above median flow yrs below median flows yrs

N = 4 N = 9 N = 10 N = 7

Expe

cted

flow

giv

en P

PT

GRE

ATER

Observed streamflow

MEDIAN > MEDIAN < High-‐flow + Low-‐flow +

  Above or below median flow years

  Flow > rela�ve to precipita�on   Below median temperatures   Soil moisture corresponds to

moisture anomalies

Water year flow, cool season precip, March-‐July temperature, and November soil moisture averaged for each set

Expe

cted

flow

giv

en P

PT

GRE

ATER

LE

SS Observed streamflow

MEDIAN > MEDIAN < High-‐flow +

Low-‐flow -‐

Low-‐flow +

  Below median flow years   Flow < rela�ve to precipita�on   Above median temperatures.   Soil moisture corresponds more

closely to precipita�on



moisture anomalies

Water year flow, cool season precip, March-‐July temperature, and November soil moisture averaged for each set

Expe

cted

flow

giv

en P

PT

GRE

ATER

LE

SS Observed streamflow

MEDIAN > MEDIAN <

High-‐flow -‐

High-‐flow +

Low-‐flow -‐

Low-‐flow +

  Below median flow years   Flow < rela�ve to precipita�on   Above median temperatures.   Soil moisture corresponds more

closely to precipita�on



moisture anomalies

  Above median flow years   Flow < rela�ve to precipita�on   Temperatures are not warmer

but nearly average…..

These 7 years coincide with some of the we�est ranking winters. How do they compare with 7 we�est winters with correspondingly high flows?

WETTEST COOL SEASONSWY Oct-‐Apr, percentile1973 0.9912005 0.9811941 0.9721952 0.9631979 0.9541993 0.9441980 0.9351997 0.9261942 0.9171920 0.9071909 0.8981995 0.8892011 0.8801907 0.8701986 0.8611906 0.8521985 0.8431978 0.8331917 0.8241984 0.8151929 0.8061958 0.7961999 0.7871932 0.7781914 0.7691911 0.7591916 0.750

Above median flow years with flow < ppt

We�est winters with similarly high flows

Total cool season precipita�on, in percen�le, averaged for 2 sets of years, by month

Differences in Distribu�on of Precipita�on over the Cool Season?

Oct-‐Apr cool season precipita�on we�est winters – high-‐flow<precip yrs

Seasonal pa�erns vary, but in general, the we�est winters with correspondingly high flows show greater precipita�on in headwaters regions, par�cularly for the Yampa, main stem, and Gunnison.

Mean temperature, in percen�le, averaged for 2 sets of years, by month

Differences in Average Monthly Temperatures, March-‐July?

March mean temperature we�est winters – high-‐ flow <precip yrs

March mean temperature we�est winters – high-‐ flow <precip yrs

In the in contrast to the years with flow < precipita�on, in the we�est winters , March temperatures are cooler, especially in the upper por�on of the Upper Basin. In July, temperatures are slightly cooler in these years, except in the southwestern part of the basin.

July mean temperature we�est winters – high-‐flow<precip yrs

One more thing: If we just use these 30 years – when the difference between flow and cool season precipita�on is greater than 1 standard devia�on – what variables best es�mate water year flow?

As before, stepwise model with pool of 6 predictors:   Oct-‐Apr precipita�on   March, March-‐May, Mar-‐Jul temperature   Oct , Nov soil moisture

But n = 30 years

Lees Ferry flow, years difference between flow and cool season precipita�on > 1 standard devia�on: Regression model

Step Multiple Multiple R-‐square F -‐ to p-‐level+in/-‐out R R-‐square change entr/rem

Mar-‐Jul T 1 0.647 0.419 0.419 20.190 0.000Oct-‐Apr P 2 0.781 0.611 0.192 13.281 0.001Oct soil 3 0.831 0.691 0.081 6.802 0.015

Summary

  Spring/summer temperatures do not explain a large part of the total variance in water year flow, but….

  In years when the difference between cool season precipita�on and flow is greatest, temperatures may be especially influen�al (in high flow years, with even we�er winters, this rela�onship is a bit less straigh�orward).

Some related follow-‐up ques�ons from Denver Water and Colorado River District visits this summer: 1. In the regression model using climate variables to es�mate Lees Ferry water year flow, a) do models for more recent years look different? And b) does adding water year precipita�on or summer precipita�on to the predictor pool change anything? 2. Analysis for sub-‐basins – any differences, especially between San Juan Dolores and Green/Yampa?

1. For the model of Lees WY flow, what happens if we look at different periods of �me? Lees Ferry modeling with different �me periods (1960-‐2012, 1973-‐2012, 1983-‐2012): Using same pool, Oct-‐Apr precip, Apr T, Mar-‐May T, Mar-‐Jul T, Oct soil m, Nov soil m Li�le difference in models for the 3 sub-‐periods:   All had Oct-‐Apr precip as 1st step, explaining about 70% of the variance (> than for the full period)

  All had a temperature variable as 2nd (Mar-‐Jul, except 1972-‐2012 was April instead), ~6% variance explained.

  All had Nov soil as 3rd (3%, 2%, 4% added variance explained)

2. What happens if we add water year precipita�on as a poten�al predictor?   Full period: the same model resulted, but WY precipita�on entered as 4th variable, explaining 2% of the variance.

  Similar result for 1960-‐2012, but WY precip is not significant as a predictor (4th variable, 1% explained)

  For the 30-‐ and 40-‐yr sub periods (1973-‐2012, 1983-‐2012), WY precip replaced Oct-‐Apr precip as 1st predictor)*

*Some of this could be due to climate data issues?.

3. What if spring/summer precipita�on is added to the pool as a poten�al predictor? May, June, July, May-‐June-‐July (MJJ) and May-‐Aug (MJJA) precipita�on were added to the pool   For the full period, a�er Oct-‐Apr P and Mar-‐Jul T, July P entered as the 3rd variable (3%), then Nov soil (2%) then MJJA precip (1%)

  In the 3 sub-‐periods, July P or Aug P entered a�er Oct-‐Apr or WY precip (2nd or 3rd predictor)

Years when flow and cool season precip differences are > 1 standard devia�on

Sub-‐basin results: Ex

pect

ed fl

ow g

iven

PPT

GRE

ATER

LE

SS

Observed streamflow:Green/Yampa

MEDIAN > MEDIAN <

High-‐flow + Low-‐flow +

High-‐flow -‐ Low-‐flow -‐

MEDIAN > MEDIAN <

Observed streamflow

MEDIAN > MEDIAN <

High-‐flow -‐

High-‐flow +

Low-‐flow -‐

Low-‐flow +

Expe

cted

flow

giv

en P

PT

GRE

ATER

LE

SS

High-‐flow + Low-‐flow +


Green/Yampa San Juan/Dolores*

13

3

11 4

12 5 14

6

Years when flow and cool season differences are > 1 standard devia�on

Sub-‐basin results

*San Juan/Dolores regression model selected Oct instead of Nov soil moisture; the only difference in the sub-‐basin models

Observed streamflow

High-‐flow -‐

High-‐flow +

Low-‐flow -‐

Low-‐flow + 10

9 7

4

MEDIAN > MEDIAN <

Green/Yampa San Juan/Dolores

MEDIAN > MEDIAN < MEDIAN > MEDIAN <

UCRB

13 6

5 14 12

11 4

3

Years when flow and cool season differences are > 1 standard devia�on

UCRB and sub-‐basin comparison <

Exp

ecte

d flo

w g

iven

PPT

>

Distribu�on of years with flow/cool season precipita�on differences > 1 standard devia�on

Expe

cted

flow

g

iven

PPT

>

<

Observed streamflow

MEDIAN > MEDIAN < High-‐flow + Low-‐flow +


Discussion

  Resource management feedback, needs, challenges for using these results, sugges�ons for addi�onal work

  Research challenges -‐ Climate data uncertain�es: Steph McAfee, Greg Pederson, Greg McCabe -‐ Measuring antecedent moisture; sources, op�ons and alterna�ves? Baseflows?

Climate data uncertain�es Steph McAfee, Greg Pederson, Greg McCabe

Baseflows have been suggested as a be�er metric for antecedent moisture condi�ons

Colorado River at Cameo, es�mated base flow and water year streamflow, 1983-‐2012

baseflow

streamflow

Lunch!

PART 2. Using tree-‐ring reconstruc�ons of antecedent soil moisture, temperature, and precipita�on for past centuries, are contribu�ons of these three factors to low flows over past centuries similar to those of the 20th and 21st century? Are there differences in these contribu�ons between cooler and warmer �me periods? Have contribu�ons changed over �me? What are common or unusual sets of clima�c and spa�al factors that have led to low flows in the past?

In progress:

Preliminary results for Reconstruc�ons

  Reconstruc�ng Antecedent Soil Moisture Using Tree Rings: Becky Brice

  Can a mul�-‐proxy approach to tree-‐ring data be used to reconstruct temperature? Adam Csank

  Comparing reconstruc�ons of precipita�on and streamflow: Connie Woodhouse

Reconstruc�ng Antecedent Soil Moisture Using Tree Rings

Becky Brice

Can a mul�-‐proxy approach to tree ring data be used to reconstruct temperature? Adam Csank

Comparing reconstruc�ons of UCRB cool season precipita�on and water year streamflow

Connie Woodhouse

  4 predictor chronologies in the model   70% of the variance explained

Observed and reconstructed UCRB October-‐April Precipita�on, 1906-‐1999

Reconstructed Lees Ferry flow and October-‐April total precipita�on, in percen�les, 1906-‐1997

flow greater rela�ve to precip

flow less rela�ve to precip

Gray bar = 1 standard devia�on from the mean; these are years when Lees WY flow is markedly greater or less than Oct-‐Apr total precipita�on (ver�cal bars are individual years)

Reconstructed Lees Ferry flow and October-‐April total precipita�on, 1906-‐1997

Reconstructed (top) and observed (bo�om) Lees Ferry flow and October-‐April total precipita�on, 1906-‐1997/2012

Ver�cal bars are years when Lees WY flow is > 1 SD greater (blue) or less (orange) than Oct-‐Apr total precipita�on percen�le values.

Correla�on comparison: Observed WY Lees flow & Oct-‐Apr precip, r = 0.820 Reconstructed WY Lees flow & Oct-‐Apr precip, r = 0.836

Reconstructed and observed differences between Lees Ferry flow and October-‐April total precipita�on, 1906-‐1997

Reconstructed Lees Ferry flow minus October-‐April total precipita�on 1569-‐1997

Reconstructed Lees Ferry flow minus October-‐April total precipita�on 1569-‐1997

Period with flow o�en less than expected given Oct-‐Apr precipita�on…..Warmer??? Drier antecedent condi�ons???

Ques�ons, comments, sugges�ons?

PART 3. What is the sensi�vity of UCRB low flows to different scenarios of changes in antecedent soil moisture, winter precipita�on, and winter/spring temperatures projected by CMIP5 models? Do “no-‐analog” sets of seasonal condi�ons exist (a warm, winter wet) and what is the impact on flow? How common are the set(s) of climate condi�ons causing past low-‐flow events in the ensembles and under what circumstances they occur (e.g., emissions scenario, �me period, model)? We Need Feedback on this part especially!

Op�ons for exploring future climate impacts on the UCRB

Steph McAfee

Discussion   Are we heading in the right direc�on on the research ques�ons?

  What kinds of informa�on, data, and products would be useful to you?

Wrap up   Plans for the next (and final) year of the project

  Advice on the final project workshop (for broader resource management audience; whom to invite?)

disentangling the inﬂuence of temperature and antecedent ... · temperature and antecedent soil...

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