California Drought Projections Based on Climate Change Models’ Effects on Water Availability

Future streamflow in California, as predicted by eight climate projections models, and their effects on water availability are discussed in this paper. The unimpaired projected streamflow for eleven California rivers, collected from Cal-Adapt Streamflow are compared with their unimpaired historical flows (1950-2015) using eight climate model projections (2020-2099) developed by Scripps Institution of Oceanography’s Routed Streamflow Projections; Warm Dry RCP 4.5, Average RCP 4.5, Cool Wet RCP 4.5, Other RCP 4.5, Warm Dry RCP 8.5, Average RCP 8.5, Cool Wet RCP 8.5, Other RCP 8.5. Projected drought quantities, durations, and intensities are statistically tested against historical values to determine significance of differences between past streamflow and future streamflow. The models predict significant differences between historical and projected streamflows with all three drought categories (quantity, duration, intensity), using difference in means t-tests. Warm Dry and Other climate models are projected to have larger droughts (2-3 times larger) than the historical record. Average and Cool Wet climate models are projected to have fewer droughts than the historical period. Results are consistent for 4.5 and 8.5 RCP scenarios. Potential impacts of such streamflow variations are discussed