Date of Award

Spring 1-1-2018

Document Type

Thesis

Degree Name

Master of Science (MS)

First Advisor

Jennifer E. Kay

Second Advisor

Michael Alexander

Third Advisor

Julie Lundquist

Abstract

Colorado River Basin (CRB) water management has become more challenging in recent years due to small supply changes and large demand changes. CRB supply is largely determined by the condition of Upper Colorado River Basin (UCRB) snowpack at the end of winter. This paper examines historical differences in precipitation between the Upper and Lower Colorado River Basin (LCRB) and the relationship between precipitation and large-scale atmospheric features, including circulation and vapor transport patterns during December-January-February from 1920-2009.

Precipitation commonly occurs over most of the UCRB and LCRB during the same winter season. Precipitation over the northern third of the UCRB is more closely related to northwest US precipitation instead of the rest of the CRB, suggesting a northerly moisture pathway dependence. The remainder of the CRB accumulates precipitation when moisture is transported from the southwest of the region. Wet UCRB seasons depend on a northwest US-centered trough pattern, enhanced vapor transport from the southwest, and enhanced relative moisture content; opposite conditions result in dry UCRB seasons. The results of this study can be incorporated by water management as part of the Bureau of Reclamation’s ongoing use of an adaptive management approach. Increased understanding of the physical drivers of CRB precipitation can better equip water management decisions to make skillful seasonal water supply forecasts.

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