Chris Pyke, Thomas Johnson US EPA, National Center for Environmental Assessment

1. Understanding the sensitivity of Chesapeake Bay restoration goals to climate variability and change Chris Pyke, Thomas Johnson US EPA, National Center for Environmental Assessment John Kittle Jr., John Imhoff, Mark Gray Aqua Terra Consultants The views expressed in this presentation are those of the authors and do not necessarily reflect the views or policies of the U.S. Environmental Protection Agency

2. Presentation overview • Introduction: impacts and implications of climate change for water resources • Watershed hydrology: Understanding the sensitivity of water quality endpoints to climate variability and change • Decision assessment: Identifying climate-sensitive management practices and restoration activities

3. Climate and Water Resources Management • Managing the risk associated with seasonal to inter-annual climate variability is a focus of water management • Past is typically assumed a guide to the future • Long term trends in climate may lead to unprecedented conditions and events, increasing the risk of harmful system impacts

4. Temperature Trends (1901-1998) Red = increase Blue = decrease Source: NCDC/NESDIS/NOAA

5. Precipitation Trends (1901-1998) Green = increase Brown = decrease Source: NCDC/NESDIS/NOAA

6. Geographic shifts in climatic conditions Source: Frumhoff et al. 2006 Climate change in the NE United States

7. Changes in three indices of extreme precipitation Source: Frumhoff et al. 2006 Climate change in the NE United States (GFDL and PCM models)

8. Changes in May-October streamflow Source: Frumhoff et al. 2006 Climate change in the NE United States (GFDL and PCM models)

9. Achieving goals under changing conditions Achieving water quality and living resource restoration goals under changing climatic conditions requires consideration of: • What are the potential impacts of climate change on management endpoints (water quantity and quality)? • Will changes in climate exacerbate or ameliorate the impacts of other stressors? • How will management strategies perform under changing climatic conditions?

10. Research activities • Monocacy case study: Identifying sensitivity of key endpoints to climate change • Assistance with 2030 assessment: Providing scenarios for Bay-wide sensitivity assessment using the Phase V watershed model • Decision assessment: Understanding the potential sensitivity and adaptive value of Best Management Practices and living resource restoration activities

11. BASINS Climate Assessment Tool • Collaboration between OW/OST and ORD/NCEA GCRP • New capabilities for assessing the influence of climate variability and change on hydrologic and water quality endpoints using the BASINS modeling system (BASINS-HSPF) • Functions include - Modify or generate new weather time series - Post-processing, calculate endpoints - Iteratively run the model to facilitate conduct of sensitivity assessments

12. Modify or Generate New Weather Time Series • Modify historical precipitation and temperature • apply standard arithmetic operators over any desired time interval • add events such as design events • Create new time series based on historic or modified monthly weather statistics using the stochastic weather generator CLIGEN

13. Calculate Assessment Endpoints • Post-processing capability to calculate various hydrologic and water quality endpoints, e.g. • any x-year, y-duration high or low flow event • annual water yields or mass loads

14. Sensitivity Assessments - Why? • Climate models currently have limited skill in predicting climate at the regional and local scales needed by managers • Managers can best assess their exposure to climate-related risks by understanding the hydrologic sensitivity of key management goals to a range of plausible climatic conditions and events

15. …Can Assess Risk in Reverse “What change in climate would need to occur to cause a harmful system impact?” Examples: What ∆ precipitation ∆ water yield∆ reservoir operations What ∆ air temp∆ water temp harmful to fish

16. = historical average climate (pounds/yr) Example: Sensitivity of Annual Nitrogen Loading to Changes in Temperature and Precipitation

17. Screenshot: BASINS 4 Main Screen

18. Screenshot: Climate Assessment Tool Endpoint: specify hydrologic or water quality endpoint to be considered Input: specify changes in climate to be considered

19. Screenshot: Climate Assessment Tool Results: tabular output data Pivot: pivot table

20. Monocacy watershed • Case study: Demonstrate capabilities of BASINS CAT • Evaluate climate scenarios: Consider a wide range of plausible future conditions • Integrated sensitivity assessment: Consider combinations of climate, land use, and BMP scenarios

21. Bay-wide assessment • Use the Monocacy case study as a foundation to develop “ready-to-run” set of climate scenarios for the Phase V model • Help CBP develop integrated climate and land use scenarios for the 2030 assessment

22. Anticipated outcomes • GCRP research will help CBP begin to understand the sensitivity of water quality endpoints to climate change • GCRP will help CBP use climate information in the Phase V modeling system to evaluate the sensitivity of water quality endpoints to combinations of climate and land use change • This analysis will provide a preliminary assessment of the need for more in-depth study of hydrologic sensitivity and adaptive strategies

23. Performance of practices and activities Chesapeake Bay “decision assessment” attempts to identify adaptive opportunities based on: • Sensitivity of systems to climate change • Sensitivity of practices or activities to climate change • Context and characteristics of decision making associated with individual practices and activities

24. Rationale for decision assessment Decision assessment includes research to: • Understand the characteristics of decisions • Identify climate-related decisions relevant to adaptation • Prioritize decision support resources Information Tools Decision attributes

25. Elements of decision assessment Build a foundation of decision attribute data including: • Decision characteristics: cost, frequency, reversibility • Decision context: rules, regulations, dependencies, technology • Decision impacts: economic, organizational, environmental Decision assessment Decision inventory

26. Emissions Inventory Decision Inventory The U.S. Adaptive Decision Inventory Decision inventory products • Inventory of emissions sources • Foundation for mitigation policy • Inventory of adaptation decisions • Foundation for adaptation policy

27. Take home messages • Climate is changing and this may have significant implications for the long term goals of the Chesapeake Bay program • We can use sensitivity analysis to understand the vulnerability of Bay program goals, such as TMDLs, to these changes. • We can also consider the sensitivity and adaptive value of specific restoration practices and activities

28. End The views expressed in this presentation are those of the authors and do not necessarily reflect the views or policies of the U.S. Environmental Protection Agency.