Date of Award:

8-2020

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Watershed Sciences

Committee Chair(s)

Jiming Jin

Committee

Jiming Jin

Committee

Patrick Belmont

Committee

David Stevens

Abstract

This study assessed how vegetation will influence long-term runoff trends across the western United States (western US) in the future. I used a land surface model with improved dynamic vegetation root processes to better quantify regional runoff trends across five regions (Upper and Lower Colorado, Great Basin, Pacific Northwest, and California). The model was driven by statistically downscaled and bias-corrected outputs from three global climate models under the Representative Concentration Pathway 4.5 and 8.5 scenarios. Vegetation greening dominated significant transpiration increases that contributed most to increasing evapotranspiration across the western US, especially during spring and summer. Consistent with these trends, runoff exhibited drastic reductions over these five regions, especially during summer. Annual runoff was reduced by up to -79%, -100%, -71%, -16%, and -35% across these regions, respectively. Overall, this study provides reliable fine-scale future projections of water resources for the western US and suggests that vegetation will aggravate the water crisis the western US is currently facing.

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