Reclamation Climate Change Activities Paul R. Houser

1. Reclamation Climate Change Activities Paul R. Houser

2. Reclamation Mission The mission of the Bureau of Reclamation is to manage, develop, and protect water and related resources in an environmentally and economically sound manner in the interest of the American public.

3. Observed Hydrology & Vegetation Changes Less spring snowpack TRENDS (1950-97) in April 1 snow-water content at western snow courses Less snow/more rain Stewart et al., 2005 Mote, 2003 Earlier snowmelt runoff Earlier greenup Cayan et al., 2001 Figs. M. Dettinger (USGS)

4. Implications for water supplies, water demands, operating constraints? • Supplies • warming • less snowpack  less controllable water supply • more landscape evapotranspiration (ET)  less runoff • precipitation change? could be + or - , help or worsen… • Demands • warming • Irrigation: increased seasonal water demand (longer season, more ET) • Electricity: increased summer demand, decreased winter demand • Operating Constraints • Environment – instream flow requirements? • Reduction in cold-water supplies • Flood Protection – storage reservation requirement? • All other things equal, warming leads to greater area contributing runoff during western winter storm events – greater winter reservoir drafts? • Storm intensification could be + or -, worsen or help…

5. Key Challenges for Reclamation • Understand how climate variability and change can affect Western water supply and demand, and Reclamation delivery of water given operational constraints (i.e. environmental constraints, flood constraints) • Bring science and technology to bear on the needs of water resources managers • Address goals of internal programs and authorizations where climate change is a factor

6. West-Wide Climate Risk Assessments (WWCRA) - Hydrologic Projections (2011) SECURE Report to Congress, 2011 focus on median changes; future reports have broader scope 112 Transient Climate Projections… http://gdo-dcp.ucllnl.org/downscaled_cmip3_projections/dcpInterface.html 112 Transient Hydrologic Projections covering western U.S.… Analyses of Period-changes in climate and hydrology 8 “big basin” VIC hydrology model-apps from Univ. of WA… Technical Report, data-development (TSC 86-68210, March 2011) Data-service, Reclamation and broader public use (Summer 2011) http://www.usbr.gov/WaterSMART/wwcra.html

7. SECURE Report Production • Funding • WaterSMART Basin Study Program – West-Wide Climate Risk Assessment • Supporting: • Secretarial Orders 3289 and 3297

8. Future Climate / Hydrology Baseline Change Through Time 2020s 2050s 2070s Temp Precip Snow

9. Tying to Impacts Example Colorado Flow Timing • Flow timing shifts towards additional cool season runoff. • Reduced warm season runoff • Competing Questions • Floods - Increased drawdown requirements to maintain risk objectives • Storage - Able to refill to supply objectives

10. Tying to ImpactsColorado River ExampleEnvironmental and Flood Control Implications for Flood Control Objectives Implications for Environmental Flow Objectives HUGE CAVEAT – e.g. calibration, validation

11. annual Dec-Mar Apr-Jul SECURE Report: Westwide Impacts (e.g. annual and seasonal runoff) 2020s-1990s 2050s-1990s 2070s-1990s

12. Colorado River Basin Water Supply and Demand Study

13. Annual Colorado River Water Supply & Use

14. * Additional “branches” possible depending upon assumed trajectory of specific socio-economic factors. Water Supply Scenarios * Water Demand Scenarios * Current Trends: growth, development patterns, and institutions continue along recent trends Economic Slowdown: low growth with emphasis on economic efficiency Expansive Growth: economic resurgence (population and energy) and current preferences toward human and environmental values * Enhanced Environment and Healthy Economy: expanded environmental awareness and stewardship with growing economy* Observed Resampled: • future hydrologic trends and variability will be similar to the past 100 years Paleo Resampled: • future hydrologic trends and variability are represented by the distant past (approximately 1250 years) Paleo Conditioned: • future hydrologic trends and variability are represented by a blend of the wet dry states of the paleo-climate record but magnitudes are more similar to the observed period Downscaled GCM Projected: • future climate will continue to warm with regional precipitation trends represented through an ensemble of future GCM projections * Preliminary – Subject to change

15. Integration of Supply and Demand Scenarios Water Supply Scenarios (multiple realizations for each scenario) Water Demand Scenarios Paleo Resampled Enhanced Environment and Healthy Economy Recent Trends Paleo Conditioned Current Trends Observed Resampled Recent Trends Expansive Growth Economic Slowdown Downscaled GCM Projected Climate indexing for demands

16. Addressing an Uncertain Future • The path of major influences on the Colorado River system is uncertain and can not be represented by a single view • An infinite number of plausible futures exist • A manageable and informative number of scenarios are being developed to explore the broad range of futures Scenario Funnel

17. Thank YouQuestions?