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

Transcription

1 Disentangling the Influence of Temperature and Antecedent Soil Moisture on Colorado River Water Resources Project start and duraon: September 1, 2014, 24 months Funder: U.S. Department of the Interior, Southwest DOI Climate Science Center Research partners: Adam Csank: Desert Research Instute Steph McAfee: University of Nevada, Reno Greg Pederson: USGS- Bozeman Greg McCabe: USGS- Denver Steve Gray: USGS- Anchorage Water management partners: Bureau of Reclamaon, Lower Colorado District Colorado River District (State of CO) Denver Water, Colorado NOAA Colorado Basin River Forecast Center Salt River Project, Arizona

2 Disentangling the Influence of Temperature and Antecedent Soil Moisture on Colorado River Water Resources Purpose of the workshop: Year 1 assessment and Year 2 direcons for this project Plan for the Day (workshop agenda): Summary of results to date (instrumental data analysis) Work in progress (tree- ring reconstrucons) Planning for future climate impacts analysis Feedback, quesons, discussion, comments, suggesons throughout! Introducons

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

4 Data Gridded climate data from PRISM for total monthly precipitaon, average monthly temperature (4 km resoluon) Monthly soil moisture storage from McCabe and Wolock (2011) monthly water balance model Water year natural flow esmates for the Colorado River at Lees Ferry and major tributaries Analysis period: Data have been converted to percenles in comparave analyses Analysis Variables October- April total precipitaon March, March- May, March- July average temperature October or November soil moisture

5 Selecon of temperature, precipitaon, and soil moisture variables for analysis Correlaons with Colorado R Lees water year flow, (prior July September) Monthly total precipitaon Monthly mean temperature correlaons correlaons * Oct- April total precipitaon April, March- Apr- May, and March- July average temperature 5

6 Antecedent soil moisture assessment Correlaons of Lees Ferry water year flow with soil moisture storage and monthly flows for the common years, , prior October to September. correlaon 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 correlaons with flow than CBRFC and monthly flows) October and November selected, based in large part on our hypothesis of antecedent soil moisture influence

7 Quanfying the contribuon of cool season precipitaon, temperature, and antecedent soil moisture in water year flow Stepwise model with pool of 6 predictors: Oct- Apr precipitaon 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 MarJulT novsoil March- July temperature accounts for only 8% of the total variance explained, but is it more important in certain

8 Colorado River at Lees Ferry, natural flows, Major Droughts* *using definion from Drought Catalog for Reclamaon - below average flows broken by no more than 1 year of above average flow

9 Average values for each hydroclimac variable across all years in a given drought period, color coded by drought 9

10 1930s Individual years with in major droughts: percenle values of WY flow, and variables that influence flow 1950s 2000s

11 1930s Individual years with in major droughts: percenle values of WY flow, and variables that influence flow 1950s 2000s

12 Lees Ferry flow and October- April total precipitaon, in percenles

13 Lees Ferry flow and October- April total precipitaon, in percenles flow greater relave to precip flow less relave to precip Gray bar = 1 standard deviaon from the mean; these are years when Lees WY flow is markedly greater or less than Oct- Apr total precipitaon (vercal bars are individual years)

14 Trend in March- July average temperature,

15 A closer look: 4 flavors of years Colorado River flow

16 A closer look: 4 flavors of years Colorado River flow Years with flow > precipitaon above median flow yrs below median flows yrs Years with flow < precipitaon above median flow yrs below median flows yrs N = 10 N = 4 N = 7 N = 9 Water year flow and cool season precipitaon, averaged for each set of years

17 Observed streamflow Expected flow given PPT GREATER > MEDIAN < MEDIAN High- flow + Low- flow + Above or below median flow years Flow > relave to precipitaon 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

18 Observed streamflow Expected flow given PPT GREATER LESS > MEDIAN < MEDIAN High- flow + Low- flow + Low- flow - Above or below median flow years Flow > relave to precipitaon Below median temperatures Soil moisture corresponds to moisture anomalies Below median flow years Flow < relave to precipitaon Above median temperatures. Soil moisture corresponds more closely to precipitaon Water year flow, cool season precip, March- July temperature, and November soil moisture averaged for each set

19 Observed streamflow > MEDIAN < MEDIAN High- flow + Low- flow + Above or below median flow years Flow > relave to precipitaon Below median temperatures Soil moisture corresponds to moisture anomalies Expected flow given PPT GREATER LESS High- flow - Low- flow - Below median flow years Flow < relave to precipitaon Above median temperatures. Soil moisture corresponds more closely to precipitaon Above median flow years Flow < relave to precipitaon Temperatures are not warmer but nearly average..

20 These 7 years coincide with some of the weest ranking winters. How do they compare with 7 weest winters with correspondingly high flows? Above median flow years with flow < ppt Weest winters with similarly high flows WETTEST COOL SEASONS WY Oct- Apr, percentile

21 Differences in Distribuon of Precipitaon over the Cool Season? Total cool season precipitaon, in percenle, averaged for 2 sets of years, by month

22 Oct- Apr cool season precipitaon weest winters high- flow<precip yrs Seasonal paerns vary, but in general, the weest winters with correspondingly high flows show greater precipitaon in headwaters regions, parcularly for the Yampa, main stem, and Gunnison.

23 Differences in Average Monthly Temperatures, March- July? Mean temperature, in percenle, averaged for 2 sets of years, by month

24 March mean temperature weest winters high- flow <precip yrs

25 March mean temperature weest winters high- flow <precip yrs In the in contrast to the years with flow < precipitaon, in the weest winters, March temperatures are cooler, especially in the upper poron of the Upper Basin. July mean temperature weest winters high- flow<precip yrs In July, temperatures are slightly cooler in these years, except in the southwestern part of the basin.

26 One more thing: If we just use these 30 years when the difference between flow and cool season precipitaon is greater than 1 standard deviaon what variables best esmate water year flow?

27 Lees Ferry flow, years difference between flow and cool season precipitaon > 1 standard deviaon: Regression model As before, stepwise model with pool of 6 predictors: Oct- Apr precipitaon March, March- May, Mar- Jul temperature Oct, Nov soil moisture But n = 30 years Step Multiple Multiple R- square F - to p- level +in/- out R R- square change entr/rem Mar- Jul T Oct- Apr P Oct soil

28 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 precipitaon and flow is greatest, temperatures may be especially influenal (in high flow years, with even weer winters, this relaonship is a bit less straighorward).

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

30 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 ( , , ): Using same pool, Oct- Apr precip, Apr T, Mar- May T, Mar- Jul T, Oct soil m, Nov soil m Lile difference in models for the 3 sub- periods: All had Oct- Apr precip as 1 st step, explaining about 70% of the variance (> than for the full period) All had a temperature variable as 2 nd (Mar- Jul, except was April instead), ~6% variance explained. All had Nov soil as 3 rd (3%, 2%, 4% added variance explained)

31 2. What happens if we add water year precipitaon as a potenal predictor? Full period: the same model resulted, but WY precipitaon entered as 4 th variable, explaining 2% of the variance. Similar result for , but WY precip is not significant as a predictor (4 th variable, 1% explained) For the 30- and 40- yr sub periods ( , ), WY precip replaced Oct- Apr precip as 1 st predictor)* *Some of this could be due to climate data issues?.

32 3. What if spring/summer precipitaon is added to the pool as a potenal predictor? May, June, July, May- June- July (MJJ) and May- Aug (MJJA) precipitaon were added to the pool For the full period, aer Oct- Apr P and Mar- Jul T, July P entered as the 3 rd variable (3%), then Nov soil (2%) then MJJA precip (1%) In the 3 sub- periods, July P or Aug P entered aer Oct- Apr or WY precip (2 nd or 3 rd predictor)

33 Years when flow and cool season precip differences are > 1 standard deviaon Sub- basin results: Observed streamflow:green/yampa > MEDIAN < MEDIAN High- flow + Low- flow + Expected flow given PPT GREATER LESS High- flow - Low- flow -

34 Years when flow and cool season differences are > 1 standard deviaon Sub- basin results Green/Yampa > MEDIAN < MEDIAN Observed streamflow San Juan/Dolores* > MEDIAN < MEDIAN 14 High- flow + 5 Low- flow + 12 High- flow + 3 Low- flow + Expected flow given PPT GREATER LESS 6 High- flow - 13 Low- flow - 4 High- flow - 11 Low- flow - *San Juan/Dolores regression model selected Oct instead of Nov soil moisture; the only difference in the sub- basin models

35 Years when flow and cool season differences are > 1 standard deviaon UCRB and sub- basin comparison Observed streamflow UCRB > MEDIAN < MEDIAN Green/Yampa > MEDIAN < MEDIAN San Juan/Dolores > MEDIAN < MEDIAN 10 High- flow + 4 Low- flow < Expected flow given PPT > 7 High- flow - 9 Low- flow

36 Distribuon of years with flow/cool season precipitaon differences > 1 standard deviaon Observed streamflow > MEDIAN < MEDIAN Expected flow given PPT < > High- flow + Low- flow + High- flow - Low- flow -

37 Discussion Resource management feedback, needs, challenges for using these results, suggesons for addional work Research challenges - Climate data uncertaines: Steph McAfee, Greg Pederson, Greg McCabe - Measuring antecedent moisture; sources, opons and alternaves? Baseflows?

38 Climate data uncertaines Steph McAfee, Greg Pederson, Greg McCabe

39 Baseflows have been suggested as a beer metric for antecedent moisture condions

40 Colorado River at Cameo, esmated base flow and water year streamflow, baseflow streamflow

41 Lunch!

42 In progress: PART 2. Using tree- ring reconstrucons of antecedent soil moisture, temperature, and precipitaon for past centuries, are contribuons of these three factors to low flows over past centuries similar to those of the 20th and 21st century? Are there differences in these contribuons between cooler and warmer me periods? Have contribuons changed over me? What are common or unusual sets of climac and spaal factors that have led to low flows in the past?

43 Preliminary results for Reconstrucons Reconstrucng 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 reconstrucons of precipitaon and streamflow: Connie Woodhouse

44 Reconstrucng Antecedent Soil Moisture Using Tree Rings Becky Brice

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

46 Comparing reconstrucons of UCRB cool season precipitaon and water year streamflow Connie Woodhouse

47 Observed and reconstructed UCRB October- April Precipitaon, predictor chronologies in the model 70% of the variance explained

48 Reconstructed Lees Ferry flow and October- April total precipitaon, in percenles,

49 Reconstructed Lees Ferry flow and October- April total precipitaon, flow greater relave to precip flow less relave to precip Gray bar = 1 standard deviaon from the mean; these are years when Lees WY flow is markedly greater or less than Oct- Apr total precipitaon (vercal bars are individual years)

50 Reconstructed (top) and observed (boom) Lees Ferry flow and October- April total precipitaon, /2012 Vercal bars are years when Lees WY flow is > 1 SD greater (blue) or less (orange) than Oct- Apr total precipitaon percenle values.

51 Reconstructed and observed differences between Lees Ferry flow and October- April total precipitaon, Correlaon comparison: Observed WY Lees flow & Oct- Apr precip, r = Reconstructed WY Lees flow & Oct- Apr precip, r = 0.836

52 Reconstructed Lees Ferry flow minus October- April total precipitaon

53 Reconstructed Lees Ferry flow minus October- April total precipitaon Period with flow oen less than expected given Oct- Apr precipitaon..warmer??? Drier antecedent condions???

54 Quesons, comments, suggesons?

55 PART 3. What is the sensivity of UCRB low flows to different scenarios of changes in antecedent soil moisture, winter precipitaon, and winter/spring temperatures projected by CMIP5 models? Do no- analog sets of seasonal condions exist (a warm, winter wet) and what is the impact on flow? How common are the set(s) of climate condions 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!

56 Opons for exploring future climate impacts on the UCRB Steph McAfee

57 Discussion Are we heading in the right direcon on the research quesons? What kinds of informaon, data, and products would be useful to you?

58 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?)

59 OTHER SLIDES

60 Correlaons between soil moisture capacity from the CBRFC model (CBF), soil moisture storage from the McCabe/Wolack water balance model (WBM), and monthly Colorado River at Lees Ferry flows (Lees monthly flows), for the common years, oct nov dec jan feb mar apr may jun jul aug sep CBF- WBM WBM- Lees monthly flows CBF - Lees monthly flows All values are significant at p < 0.05

61 Addendum on regression models explained Lees Ferry water year flow, with cool season precipitaon, March- July temperatures, and November soil moisture (model on slide 7). The following graphics highlight what flow years are most improved with, first, the addion of temperature in the regression model (along with precipitaon), then with both temperature and November soil moisture.

62 Colorado river flow values (in percenle) for the 10 years with the most improved fit when temperature is added to the precipitaon- only model Colorado river flow values for the 10 years with the most improved fit when soil moisture is added to the precipitaon + temperature model

63

64 Summary With respect to the regression model: While cool season precipitaon explains most of the variance in water year flow, temperatures may contribute in low flow years, while soil moisture may influence flows in the very weest years

65 The Role of Temperature (and soil moisture) in Mediang Relaonships between Cool Season Precipitaon and Water Year Streamflow in the UCRB Connie Woodhouse, University of Arizona With Adam Csank (Desert Research Instute), Steph McAfee (Univ. of Nevada, Reno), Greg Pederson (USGS- Bozeman), Greg McCabe (USGS- Denver), and Steve Gray (USGS- Anchorage) This work is being funded by a DOI Southwest Climate Science Center grant.