Climate Change & California’s Water Future

1. Climate Change & California’s Water Future Jay R. Lund, Tingju Zhu, Stacy K. Tanaka, Marion W. Jenkins, Richard E. Howitt, Manuel Pulido, Melanie Taubert, Randall Ritzema, Inês Ferreira, Sarah Null Civil & Environmental Engineering Agricultural & Resource Economics University of California, Davis http://cee.engr.ucdavis.edu/faculty/lund/CALVIN/

2. In Hades, thirsty Tantalus was burdened to have water rise to his neck threatening to drown him, but receded when he stooped to drink. Above him was a boulder, threatening to crush him at some uncertain future time. Tantalus How like California water management!

3. "Change has considerable psychological impact …. To the fearful it is threatening because …things may get worse. To the hopeful it is encouraging because things may get better. To the confident it is inspiring because the challenge exists to make things better. … One’s character and frame of mind determine how readily he brings about change and how he reacts to change that is imposed on him." - King Whitney Jr. Change

4. Climate Change in California Historical, Pre-historical, Future Adaptation to Climate Warming Warming and water demand scenarios Options for adaptation Analysis for promising adaptations and performance Conclusions Overview

5. Roughly 100 years of record Two 6-year droughts One 2-year drought Other odd dry years Correlation of droughts with Pacific Decadal Oscillation (PDO) – Scripps, and others Historical climate variability

6. Last 1,000 years Scott Stine - Lake with long droughts Meko – Streamflow fluctuations – tree rings Others – Long term lake fluctuations – PDO connection for some droughts Earlier Holocene (10,000 years) Multi-decade and Multi-century droughts – lake and estuary sediments Tahoe reaches sill 3,000 years ago Pre-historical variability

7. Steady long-term rise since Ice Age’s end Delta is a drowned river valley, < 10,000 years old California has always been a dynamic place? Past sea level rise

8. Sea level rise Climate Variability Climate Warming Other forms of climate change? Future Climate Changes

9. Certain occurrence Rate is significant, but somewhat uncertain (about 1ft/century?) Some coastal implications Potential Delta water quality and flooding implications in 50-100 years (Anderson) Future sea level rise

10. Almost certain to continue. El Nino Southern Oscillation – ENSO Pacific Decadal Oscillation – PDO Other forms of variability? Future Climate Variability

11. Seems very likely Some effects already seen in California? Earlier snowmelt in recent decades Is it greenhouse warming or PDO change? Wet or dry warming? CO2 and other changes… Climate Warming

12. Shift in snowmelt season Changes in: Crop ETAW and yields Watershed and reservoir ET Urban water use Ecosystems (T, nutrients, CO2, etc.) Wet or dry warming? Some changes are clear, others uncertain. Climate Warming Effects?

13. Who knows? Varying solar intensity, … Still a new subject. How will different forms of climate change combine? Other forms of climate change?

14. California’s climate has always changed Maybe last century was lucky Additional climate changes seem likely Changes will affect water system operations Would changes affect system performance? How can our water system adapt? Conclusions about climate change

15. Climate Warming and Water Management • Preliminary study of climate warming for water management in California • 2100 climate warming and population growth scenarios • CALVIN model identifies promising adaptations to climate and population changes • Preliminary results • Conclusions Thanks to California Energy Commission for funding!

16. 2100 Climate Changes • Water availability changes estimated for 12 climate warming scenarios (based on LBNL). • Water supply impacts estimated for: • Major mountain inflows • Groundwater inflows • Local streams • Reservoir evaporation • Effects estimated for 113 inflows distributed throughout California

17. 2100 Climate Changes

18. Climate Scenario Average Annual Water Availability Climate Scenario Average Annual Water Availability Change maf Volume maf Change maf Vol. maf -2.1 7) HCM 2025 41.9 4.1 1) 1.5T 0%P 35.7 -0.1 8) HCM 2065 40.5 2.7 2) 1.5T 9%P 37.7 -4.1 9) HCM 2100 42.4 4.6 3) 3.0T 0%P 33.7 -0.8 10) PCM 2025 35.7 -2.1 4) 3.0T 18%P 37.1 -6.2 11) PCM 2065 32.9 -4.9 5) 5.0T 0%P 31.6 -1.6 12) PCM 2100 28.5 -9.4 6) 5.0T 30%P 36.2 0.0 Historical 37.8 2100 Raw Water Availability

19. 2100 Population & Land Use • Future population and land use will greatly affect water demands. • With growth to 92 million (UCB), urban demands grow by ~ 7.2 maf/yr • Urbanization of irrigated land reduces agricultural demands by ~ 2.7 maf/yr • Net effect is big (+4.5 maf/yr) and economically important

20. What is CALVIN? • Model of entire inter-tied California water system • Surface and groundwater systems; supply and demands • Economics-driven optimization model • Economic Values for Agricultural, Urban, & Hydropower Uses • Flow Constraints for Environmental Uses • Prescribes monthly system operation over a 72-year representative hydrology Maximizes economic performance within constraints

21. CALVIN’s Spatial Coverage Over 1,200 spatial elements 51 Surface reservoirs 28 Ground water reservoirs 600+ Conveyance Links 88% of irrigated acreage 92% of population

22. Economic Values for Water • Agricultural: Production model SWAP • Urban: Demand model based on price elasticities • Hydropower • Operating Costs: Pumping, treatment, water quality, etc. Environmental flows and deliveries as constraints – with first priority

23. Data Flow for the CALVIN Model

24. Integrated Adaptation Options • Water allocation (markets & exchanges) • System operations • Conjunctive use • Coordinated operations • Urban conservation/use efficiencies • Cropping changes and fallowing • Agricultural water use efficiencies • New technologies • Wastewater reuse • Seawater desalination

25. Model Limitations • 1) Data: • Base hydrology, Tulare Basin, • monthly agricultural demands, etc. • 2) Network flow formulation, simplified • costs, water quality, environmental requirements, hydraulics, hydrologic • foresight and coordination • 3) Limited range of benefits • No flood control or recreation

26. Alternative Conditions • Base 2020 – Current policies for 2020 • SWM 2020 – Statewide water market 2020 • SWM 2100 – SWM2020 with 2100 demands • PCM 2100 – SWM2100 with dry warming • HCM 2100 – SWM2100 with wet warming

27. Climate Scenarios by Region

28. Some Early Results • Delivery, Scarcity, and Economic Performance • Conjunctive Use and other Operations • New Technologies • Costs of Environmental Flows • Flood Frequency • Hydropower Performance • Economic Value of Facility Changes

29. Cost Base 2020 SWM 2020 SWM 2100 PCM 2100 HCM 2100 Urban Scarcity 1,564 170 785 872 782 Agric. Scarcity 32 29 198 1,774 180 Operating 2,581 2,580 5,918 6,065 5,681 Total Costs 4,176 2,780 6,902 8,711 6,643 Scarcity, Operating, & Total Costs($ million/yr)

30. Total Deliveries and Scarcities

31. Agricultural Deliveries & Scarcities

32. Scarcity Costs by Sector

33. Groundwater Operations

34. Conjunctive Use

35. New Source Technologies

36. Environmental Flow Costs

37. Trinity River Shadow Costs

38. Annual Flood Frequency(Lower American River)

39. Hydropower Generation

40. Economic Value of Facility Changes($/unit-yr)

41. Conclusions from Results • Climate warming’s hydrologic effects are substantiated and generalized. • Future water demands matter too! Similar magnitude to climate warming effects. • Must also allow future adaptations – Optimization. • California’s system can adapt, at some cost.

42. Conclusions from Results (con’t) • Central Valley agriculture sensitive to dry warming • Urban S. Calif. less sensitive to warming • Flooding problems • Adaptation would be challenging Institutional flexibility needed to respond to both population and climate changes. • Study has limitations. But it is worthwhile considering management and policy changes.

43. Glimpse at Long-term Future • Integrated mix of management options: Water use efficiency, conjunctive use, water transfers, reuse, desalination, … • Importance of local and regional actions in a statewide context. • Long-term importance of flexibility. • Some scarcity is optimal. http://cee.engr.ucdavis.edu/faculty/lund/CALVIN/