1. Alan F. Hamlet, Nathalie Voisin, Dennis P. Lettenmaier, David W. Pierce Center for Science in the Earth System Climate Impacts Group and Department of Civil and Environmental Engineering University of Washington Scripps Institute of Oceanography California Energy Commission January, 2005 Effects of Climate Variability on Hydropower Production and Energy Demand in CA and the PNW

2. Background

3. Effects of the PDO and ENSO on Columbia River Summer Streamflows Cool Warm PDO Red=warm ENSO Green=ENSO neutral Blue=cool ENSO

4. Value of Long-Range Streamflow Forecasts for PNW Hydro Marketing ~ $150 million/yr This value is created in part by marketing additional energy in late summer (when energy is more valuable) in expected wet years. Hamlet, A.F., Huppert, D., Lettenmaier, D.P., 2002, Economic Value of Long-Lead Streamflow Forecasts for Columbia River Hydropower, ASCE J. of Water Res. Planning and Mgmt, 128 (2), pp 91-101

5. http://www.abb.com/global/abbzh/abbzh251.nsf!OpenDatabase&db=/global/gad/gad 02181.nsf&v=17EA&e=us&m=100A&c=C1256D71001E0037C1256B8000371E41 ~8000 MW Intertie Capacity In normal or above normal water years in the PNW, net transfers are typically from PNW to CA In below normal water years in the PNW, transfers from CA to PNW can occur in winter and transfers from PNW to CA in spring and summer may be reduced or suspended.

6. Research Questions: How do hydropower resources in the PNW and CA vary with climate and how predictable are these variations? How does electrical demand vary with climate in the PNW and CA and how predictable are these variations? How do supply and demand co-vary in time? How predictable are energy surpluses and deficits in each region? How can we best use this information to maximize the benefits of the PNW - CA electrical intertie?

7. Tools and Methods

8. Snow Model Schematic of VIC Hydrologic Model and Energy Balance Snow Model PNW CA CR B GB

9. Met Data 1915-2003 VIC Overview of Simulation and Analysis CVMod ColSim PNW Hydro Sacramento San Joaquin Hydro Statistical Demand Models PNW Demand CA Demand Population Weighted Temperature Time Series Urban Population Data Observed Demand Data

10. Results

11. Evaluation of VIC Streamflow Simulations

12. Covariation of Normalized PNW and CA Hydropower Production California hydropower is less than 10% of total CA demand, but may play a significant role in energy trading on short time scales. R 2 =0.541

13. Evaluation of Daily Time Step Energy Demand Model Demand vs Tmax Model Validation

14. Predictability of Seasonal Demand in the PNW and CA Winter demand in the PNW is predictable with long lead times via ENSO forecasts: Warm ENSO = lower winter electrical demand Cool ENSO = higher winter electrical load Load is in phase with water availability. Summer demand in CA has been recently demonstrated to be predictable with several months lead time using the NPO (PDO) index in spring (Alfaro et al. 2005). Even longer lead times may be possible. B.Normal NPO (MAM) = lower CDD in S. CA. (JJA) A.Normal NPO (MAM) = higher CDD in S. CA. (JJA) Load is out of phase with PNW water availability.

15. Above normal surplus hydro from the PNW is more likely in cool PDO and cool ENSO years, less likely in warm PDO and warm ENSO years. Year to year variations are compressed by covariation of supply and demand (i.e. low water typically is simultaneous with low demand).

16. Probability of Exceedance for Spring Surplus Energy Resources in the PNW

17. A Forecast Timeline Jun Aug Jun On ~June 1 we have: Current Reservoir Contents ( PNW and CA ) Current Summer Streamflow Forecast (PNW and CA) ENSO forecast PDO forecast CA Demand Surplus PNW Energy for Coming Spring PNW Winter Demand Jan Forecasts: