Water Management and Climate Change in the US-Mexico Border Region

1. Robert Lempert Senior Scientist RAND Water Management and Climate Change in the US-Mexico Border Region September 27, 2008

2. Climate Change Poses Significant Challenge for Resource Planning the US-Mexico Border Region “Stationarity is dead” Many organizations already include climate (often implicitly) in their decisions Amidst all the uncertainty one thing we do know for sure -- tomorrow’s climate will not be like the past’s Changes in West are likely to include: Increased temperatures Changes in precipitation patterns More intense storms Declining snow pack and summertime river flows Without proper planning: Supply expectations may not be met Demand may grow faster than can be accommodated Infrastructure may fail

3. Planners in S. California, for Instance, Face aRange of Possible Future Climate Conditions No change Hotter Winter-time precipitation change (2000 - 2030)‏ Much drier Wetter Likely range -19% +8% 0 Summer-time temperature change (2000- 2030)‏ Likelyrange +.1C 0 +2.1C Results based on statistical summary of 21 of the world’s best Global Climate Models Water managers also face many similar, if not more, disruptive uncertainties

4. Our Work With California Water Agencies Suggests Lessons for US-Mexico Border Region Resource managers can no longer assume future climate will be like the past Despite deep uncertainty, sufficient information exists to support prudent action today Effective response options are available Legislatures may have to help ensure: Access to appropriate data and information Funding for demonstration projects and new infrastructure Appropriate incentives and perhaps some regulatory changes

5. Conducted Vulnerability and Options Analysis for Inland Empire Utilities Agency (IEUA)‏ IEUA currently serves 800,000 people May add 300,000 by 2025 Water presents a significant challenge

6. Conducted Vulnerability and Options Analysis for Inland Empire Utilities Agency (IEUA)‏ IEUA currently serves 800,000 people May add 300,000 by 2025 Water presents a significant challenge • Current water sources include: • Groundwater 56% • Imports 32% • Recycled 1% • Surface 8% • Desalter 2%

7. Conducted Vulnerability and Options Analysis for Inland Empire Utilities Agency (IEUA)‏ IEUA currently serves 800,000 people May add 300,000 by 2025 Water presents a significant challenge • Current water sources include: • Groundwater 56% • Imports 32% • Recycled 1% • Surface 8% • Desalter 2% Focus of IEUA’s 20 year plan

8. Our Research Focused on Two Key Questions Are IEUA’s plans vulnerable to assumptions about uncertain future conditions, including climate change? Which actions should IEUA do now and which can they defer to later to address the threat of climate change?

9. We Identified Three Types of Assumptions That Could Impact the Performance of IEUA Plans Natural Processes • Future temperatures • Future precipitation • Changes in groundwater processes Performance of Management Strategies • Development of aggressive waste-water recycling program • Implementation of groundwater replenishment Costs of Future Supplies and Management Activities • Imported supplies • Water use efficiency

10. We Identified Three Types of Assumptions That Could Impact the Performance of IEUA Plans Natural Processes • Future temperatures • Future precipitation • Changes in groundwater processes Performance of Management Strategies • Development of aggressive waste-water recycling program • Implementation of groundwater replenishment Costs of Future Supplies and Management Activities • Imported supplies • Water use efficiency

11. We Identified Three Types of Assumptions That Could Impact the Performance of IEUA Plans Natural Processes • Future temperatures • Future precipitation • Changes in groundwater processes Performance of Management Strategies • Development of aggressive waste-water recycling program • Implementation of groundwater replenishment Costs of Future Supplies and Management Activities • Imported supplies • Water use efficiency

12. IEUA Faces a Wide Range of Possible Future Climate Conditions Summer-time temperature change (2000- 2030)‏ No change Hotter Likelyrange +.1C 0 +2.1C Winter-time precipitation change (2000 - 2030)‏ Much drier Wetter Likely range -19% +8% 0

13. Our Simulation Model Assessed Performance of IEUA Plans in Different Future States of World IEUA Plans System data & climate forecasts Scenario A Plan generates surpluses in benign future climate Scenario B Plan suffers shortages in adverse future climate 400 400 Shortage Dry-year yield 350 350 Surplus Surplus 300 300 Imports Imports 250 250 Annual supply (taf)‏ Annual supply (taf)‏ 200 200 Local Supplies Local Supplies 150 150 Groundwater Groundwater 100 100 50 50 Recycled Recycled 0 0 2005 2010 2015 2020 2025 2030 2005 2010 2015 2020 2025 2030 Year Year Temp: +0.7oC Precip: +3% Temp: +1.6oC Precip: -10% Performance of plans Model

14. IEUA’s Ability to Implement Its Plan and The Agency’s Future Costs are Also Uncertain • Estimates of agency’s likelihood of achieving its recycling and ground water goals • Future costs of alternative sources of supply

15. Simulation Suggests that Climate Change Exacerbates Other Risks to IEUA’s Plan In 656 cases IEUA’s plan has low cost Ran simulation 1,000 times for many different combinations of uncertain factors In 344 cases IEUA’s plan has high cost What factors explain these high cost cases? Key Vulnerabilities to IEUA Plan Miss recycling goal Adverse future climate Any reduction in groundwater infiltration Factors considered Performance towards recycling goal Performance towards replenishment goal Future climate Amount of new conservation Amount of groundwater infiltration Effect of climate on imports

16. Our Research Focused on Two Key Questions Are IEUA’s plans vulnerable to assumptions about uncertain future conditions, including climate change? Which actions should IEUA do now and which can they defer to later to address the threat of climate change?

17. Response Options May Help IEUA Address These Vulnerabilities • Efficiency reduces demand but imposes costs on customers and requires customer participation • Recycled water use is a drought-proof supply but requires significant public support • Improved groundwater management increases resilience to shortages but requires significant cooperation and faces unknown costs Each Option Has Benefits and Costs

18. Should IEUA Act Now or Later to Reduce Potential Climate Vulnerabilities? In 2015, 2020, 2025, …. Monitor, and take additional action if supplies drop too low NO Implement additional efficiency, recycling, and replenishment YES Act now to augment 2005 Plan? In 2015, 2020, 2025, …. Monitor, and take additional action if supplies drop too low

19. We Evaluated Nine Strategies Under200 Scenarios Reflecting Key Uncertainties Current Plan Forever UWMP + DYY and recycling UWMP + replenishment UWMP with updates UWMP + DYY and recycling with updates UWMP + replenishment with updates UWMP + efficiency UWMP + efficiency with updates Static options Update options UWMP + all enhancements 0 20 40 60 80 100 120 Number of Scenarios (PV Costs > $3.75 billion)‏

20. Just Allowing the Current UWMP to UpdateReduces Vulnerability Substantially Current Plan Forever UWMP + DYY and recycling From 120 Down to 30 UWMP + replenishment UWMP with updates • Still vulnerable to: • Precipitation declines • Declines in imports • Costs of imports UWMP + DYY and recycling with updates UWMP + replenishment with updates UWMP + efficiency UWMP + efficiency with updates Static options Update options UWMP + all enhancements 0 20 40 60 80 100 120 Number of Scenarios (PV Costs > $3.75 billion)‏

21. Implementing Efficiency and Other Options NowReduces Future Vulnerabilities Even More UWMP with updates UWMP + DYY and recycling with updates UWMP + replenishment with updates Implementation becomes more challenging UWMP + efficiency Static options UWMP + efficiency with updates Update options UWMP + all enhancements 0 10 20 30 40 Number of Scenarios (PV Costs > $3.75 billion)‏

22. Implementing Efficiency and Other Options NowReduces Future Vulnerabilities Even More UWMP with updates UWMP + DYY and recycling with updates UWMP + replenishment with updates Implementation becomes more challenging UWMP + efficiency Static options UWMP + efficiency with updates Update options UWMP + all enhancements 0 10 20 30 40 Number of Scenarios (PV Costs > $3.75 billion)‏ IEUA should make more near-term efficiency investments; monitor performance and adapt as needed down the road

23. US-Mexico Border Region Can and Must Begin Adapting to Climate Change Resource managers can no longer assume future climate will be like the past Impacts of climate change may create significant vulnerabilities in agencies’ operations and plans Despite deep uncertainty, sufficient information exists to support prudent action New planning methods may prove necessary Key is identifying near-term actions that are robust over a wide range of plausible futures Effective response options are available Inland Empire Utilities Agency should increase investment in near-term conservation, monitor carefully, and prepare to take further actions Other agencies may require additional near-term responses

25. Analysis Suggests Three Such Driving Forces Conducted statistical, cluster-finding analysis over all the model runs to identify the factors most strongly associated with shortages in 20 Year Plan Meet recycling goal Meet replenishment goal Future climate New conservation Reduced groundwater infiltration Climate on imports Miss Meet Exceed Miss Meet Exceed Drier Wetter -5% +20% -20% 0% Weak Strong Explains 127 (of 180) low surplus cases

26. Simulation Model Evaluated IEUA’s Current Plan Under Many Different Scenarios IEUA Water Management Options Option Performance Simulation Model Uncertainties

27. Scatter Plots Summarize Supply and Shortage Costs for Each Scenario for Current Plan Current Plan Forever 4.0 PV supply cost ($ billions)‏ 3.5 3.0 2.5 1.0 2.0 3.0 4.0 0 PV shortage cost ($ billions)‏

28. Scatter Plots Summarize Supply and Shortage Costs for Each Scenario for Current Plan Modest warming and minimal precipitation decrease $3.3 billion in supply cost $0 in shortage cost Scenario B • Significant warming and precipitation decrease • $3.4 billion in supply cost • $1.9 billion in shortage cost Current Plan Forever 4.0 PV supply cost ($ billions)‏ 3.5 Scenario A 3.0 2.5 1.0 2.0 3.0 4.0 0 PV shortage cost ($ billions)‏

29. Scatter Plots Summarize Supply and Shortage Costs for Each Scenario for Current Plan Current Plan Forever 4.0 PV supply cost ($ billions)‏ 3.5 3.0 (200 Scenarios)‏ 2.5 1.0 2.0 3.0 4.0 0 PV shortage cost ($ billions)‏

30. The Current Plan Performs PoorlyUnder Many Possible Future Conditions Current Plan Forever 4.0 (120 of 200 Scenarios)‏ PV supply cost ($ billions)‏ 3.5 3.0 $3.75 billion cost threshold 2.5 1.0 2.0 3.0 4.0 0 PV shortage cost ($ billions)‏

31. Statistical Analyses Suggested Three MajorVulnerabilities to the IEUA Plan Strong declines in precipitation Reductions in imported supply Changes in groundwater replenishment Current Plan Forever 4.0 (120 of 200 Scenarios)‏ PV supply cost ($ billions)‏ 3.5 3.0 $3.75 billion cost threshold 2.5 1.0 2.0 3.0 4.0 0 PV shortage cost ($ billions)‏