Climate Change and the Chehalis River. Guillaume Mauger, Se-Yeun Lee, Christina Bandaragoda, Yolande Serra, and Jason Won September 21, 2016

Transcription

1 Climate Change and the Chehalis River Guillaume Mauger, Se-Yeun Lee, Christina Bandaragoda, Yolande Serra, and Jason Won September 21, 2016

2 Background: General Approach to Climate Impacts Assessment Global Climate Scenarios Regional Climate Scenarios Impacts Modeling Planning and Design 2

3 All Results and Methods Online Project website Model code, methods Google map 3

4 Large-scale Drivers of Heavy Rainfall Events 1. Are regional model simulations accurate? 2. Does the spatial distribution of precipitation change? 3. Do the large-scale dynamics change? 4

5 Large-scale Drivers of Heavy Rainfall Events 1. Are regional model simulations accurate? mm per day Basin Dam 41-yr value 95th Percentile Rain Events NNRP MME ECHAM5 CCSM3 CCSM4 mm per day Differences from NNRP for 95th Percentile Rain Events Basin Dam 41-yr value MME ECHAM5 CCSM3 CCSM4 5

6 Large-scale Drivers of Heavy Rainfall Events 40 mm per day th Percentile Rain Events for Basin Dam 41-yr value 1. Are regional model simulations accurate? 2. Does the spatial distribution of precipitation change? mm per day count MME ECHAM5 CCSM3 CCSM4 Differences from Historical Period ( ) Basin Dam 41-yr value Number of 95th Percentile Rain Events for Basin Dam MME ECHAM5 CCSM3 CCSM4 MME ECHAM5 CCSM3 CCSM4 Basin Dam Change in Intensity Change in Frequency Percent Difference from Historical Period ( ) % MME ECHAM5 CCSM3 CCSM4 (98th percentile) 6

7 Large-scale Drivers of Heavy Rainfall Events 1. Are regional model simulations accurate? 2. Does the spatial distribution of precipitation change? 3. Do the large-scale dynamics change? Water Vapor Wind Future Historical Future Historical Source: Warner et al

8 Hydrologic Modeling: Updated Methods, Improved Representation of Flows Improved Methods observed new old 8

9 Flooding: Projected to Increase; Wide Range Among Models Different Hydrologic Models Different Climate Change Inputs 9

10 Flooding: Uncertainty Is Larger than Differences Among Tributaries Projected Change in 100-year FLOOD for all Bias-Corrected Chehalis streamflow sites 2050s: Average for all sites and all MACA models: rawwrf, SRES A1B bcwrf, SRES A1B bcmaca, RCP 4.5 bcmaca, RCP 8.5 DHSVM VIC DHSVM VIC DHSVM VIC DHSVM VIC min max min max min max min max avg min max avg min max avg min max avg min max ChehalisR-atPorter year = +66% ChehalisR-nrDoty ChehalisR-nrGrandMound year = +35% NewaukumR-nrChehalis SatsopR-nrSatsop SkookumchuckR-blwBldyRunCr year = +16% SkookumchuckR-nrBucoda SkookumchuckR-nrVail WynoocheeR-abvBlackCr WynoocheeR-abvSaveCr WynoocheeR-nrGrisdale Projected change for 25 a high greenhouse gas -9 scenario Average: All sites Average: Key sites (*) (RCP 8.5), for 2040 to 2099 relative to 1951 to 2005 KEY: +50%: wetter 0: no change 50%: drier 2080s: rawwrf, SRES A1B bcwrf, SRES A1B bcmaca, RCP 4.5 bcmaca, RCP 8.5 DHSVM VIC DHSVM VIC DHSVM VIC DHSVM VIC min max min max min max min max avg min max avg min max avg min max avg min max ChehalisR-atPorter ChehalisR-nrDoty ChehalisR-nrGrandMound

11 Low Flows: Projected to Decrease; Smaller Range 11

12 Low Flows: Projected to Decrease; Smaller Range Projected Change in 10-year LOW FLOW for all Bias-Corrected Chehalis streamflow sites 2050s: Average for all sites and all MACA models: rawwrf, SRES A1B bcwrf, SRES A1B bcmaca, RCP 4.5 bcmaca, RCP 8.5 DHSVM VIC DHSVM VIC DHSVM VIC DHSVM VIC min max min max min max min max avg min max avg min max avg min max avg min max ChehalisR-atPorter* ChehalisR-nrDoty* year = -7-6% ChehalisR-nrGrandMound* NewaukumR-nrChehalis* year = -14% SatsopR-nrSatsop* SkookumchuckR-blwBldyRunCr SkookumchuckR-nrBucoda* SkookumchuckR-nrVail WynoocheeR-abvBlackCr* Projected change 1-56 for -24 a -18 high 4 greenhouse gas -32 scenario WynoocheeR-abvSaveCr WynoocheeR-nrGrisdale (RCP ), for to relative to to Average: All sites Average: Key sites (*) KEY: +50%: wetter 0: no change 50%: drier 2080s: rawwrf, SRES A1B bcwrf, SRES A1B bcmaca, RCP 4.5 bcmaca, RCP 8.5 DHSVM VIC DHSVM VIC DHSVM VIC DHSVM VIC min max min max min max min max avg min max avg min max avg min max avg min max ChehalisR-atPorter* ChehalisR-nrDoty*

13 Temperature and Humidity: Warmer Year-round, Drier Summers Maximum Minimum Vapor Pressure Temperature Deficit Jan Apr Jul Oct 13

14 Summary Storm dynamics (e.g., wind speeds) are not projected to change, but warming will bring heavier precipitation Flooding is projected to increase Low flows are projected to decrease Models suggest drier conditions in summer New methods have led to improved streamflow estimates, but there remains a large spread among models 14

15 Questions

16 Extra Slides The following slides are included as extras for reference during Q&A 16

17 Background: Creating Regional Climate Scenarios: Downscaling ~100 to 200 km (~60 to 120 mi) resolution ~6 km (~4 mi) resolution Downscaling Relates the Large to the Small 17

18 Background: Two Approaches to Downscaling Statistical: MACA (Multivariate Adaptive Constructed Analogs) Dynamical: WRF (Weather Research and Forecasting Model) Empirical approach Physics-based approach Figure 2. 6-hour accumulated precipitation simulated by ECHAM5/WRF for 27 Nov 2030; the left panel shows results for the outer, 36-km domain; right panel the inner, 12-km domain. 18

19 % Change in 100-year flood Background: Off-the-shelf Results Gave a Wide Range of Answers 2040s, A1B scenario, relative to 1980s Different approaches give very different answers; further refinement is needed 19