Natural Flow at Lee Ferry, AZ

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2 Natural Flow at Lee Ferry, AZ Flow measurements 30 for the Colorado River Basin Compact Annual Flow (BCM) allocated 16.5 MAF Currently used 13.2 MAF Annual Flow 10 Year Average Running Average Figure adapted from Christensen and Lettenmaier, 2007

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4 Past Studies Table from Colorado Water Conservation Board (CWCB) report Colorado Climate Change: A Synthesis to Support Water Resource Management and Adaptation. Oct 2008 (available online at:

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6 Climate Forcings GCM scenarios Historic Delta changes Regional climate models Land-surface Hydrologic Models Variable Infiltration Capacity (VIC) Noah 2.7 LSM Noah 2.8 LSM Sacramento (SAC) Catchment LSM Community Land Model (CLM) precip elasticity temp sensitivity Measures = = with time, spatially Q ref-1% - Q ref Q ref 1% Q ref Q ref Q ref 0.1 deg C

7 Seager et al GCMs, A1B scenario Christensen and Lettenmaier, GCMs, A1B scenario Non union 8 GCMs, A1B scenario Data provided by Qiuhong Tang

8 Within VIC, temp sensitivities and precip elasticities similar regardless of historic dataset or time period of long-term avgs Naturalized flow Wood and Lettemaier PRISM Maurer et al.

9 Delta method climate forcings Applied uniform perturbations in precipitation or temperature at every timestep in historic record VIC Precipitation change: related magnitude change in streamflow Temp increases: streamflow decreases annually, primarily because decreases flow in spring/summer Common across models? Where are these changes occurring? Specific land-surface characteristics? Thresholds? Base 2 ºC 1 ºC 3ºC

10 Delta method climate forcings VIC SAC CLM Catchment Base 2 ºC 1 ºC 3ºC Noah 2.7 Noah 2.8 Near Lees Ferry, flows differ between models, but models appear to have similar patterns in temp sensitivity

11 Precip: total flow difference from historic -30% +10% VIC Noah 2.7 Noah 2.8 SAC CLM Catchment Photo courtesy of xxx

12 Temp: total flow difference from historic 1ºC 3ºC VIC Noah 2.7 Noah 2.8 SAC CLM Catchment Photo courtesy of xxx

13 Precip Elasticities percent change in flow per percent increase in precip precip elast, Colo basin precip elas+city = Q ref- 1% - Q ref Q ref 1% reference precipitation (1 = historic) Photo courtesy of xxx

14 Precip Elasticities percent change in flow per percent increase in precip precip elas+city = Q ref- 1% - Q ref Q ref 1% VIC CLM Catchment Noah 2.7 Noah 2.8 SAC Photo courtesy of xxx

15 Temp Sensitivity percent change in flow per C temp increase temp sens, Colo basin (tmin&max) temp sens, Colo basin (tmin fixed) reference temp increase ( C) reference temp increase ( C) temp sensi+vity (tmin & max) = Q ref+tmin0.1&tmax0.1 Q ref 0.1 C - Q ref temp sensi+vity (tmin fixed) = Q ref+tmax0.2 Q ref 0.1 C - Q ref Photo courtesy of xxx

16 Temp Sensitivity percent change in flow per C temp increase temp sensi+vity (tmin & tmax) = Q ref+tmin0.1&tmax0.1 Q ref 0.1 C - Q ref VIC CLM Catchment Noah 2.7 Noah 2.8 SAC Photo courtesy of xxx

17 Precipitation elasticities increase with decreasing precipitation, finding consistencies between models Wet vs. dry models reflect magnitude of elasticities Temp sensitivities in most models decrease with increasing temp, although overall magnitude is larger Areas of highest runoff have more similar sensitivities and elasticities than whole basin at 1/8 degree resolution

18 Further resolve areas and seasons producing the most runoff, and their role in modulating (or exacerbating) regional scale sensitivities Investigate underlying mechanisms, i.e. differences in how temperature change is applied Explore how improved understandings of landsurface interactions and model uncertainty can aid decision-making

19 Drew Peterson, NWS River Forecast Center Ted Bohn, Univ of Washington Ben Livneh, Univ of Washington Shrad Shukla, Univ of Washington Qiuhong Tang, Univ of Washington Francisco Munoz-Arriola, Univ of Washington Research funding provided by National Oceanic and Atmospheric Administration, RISA collaboration Reconciling Colorado Flow Projections current_projects/co_river/rcn_strmflw_corvr.html