First Advisor

David A. Jay

Term of Graduation

Spring 2020

Date of Publication

7-27-2020

Document Type

Thesis

Degree Name

Master of Science (M.S.) in Civil & Environmental Engineering

Department

Civil and Environmental Engineering

Language

English

Subjects

Water temperature -- Lower Columbia River (Or. and Wash.) -- Statistics, Water temperature -- Lower Columbia River (Or. and Wash.) -- Mathematical models

DOI

10.15760/etd.7466

Physical Description

1 online resource (viii, 89 pages)

Abstract

Water temperature affects numerous aspects of aquatic life, and its stability is critical to cold water fish such as salmonids. With rising anthropogenic influence in natural environments, the future existence of these organisms is becoming less certain. In this study, I examined the evolution of historical water temperatures in the lower Columbia River by creating a statistical model to estimate daily historical water temperatures between the 1850s and 2010s. Daily air temperature and river flow measurements were used as inputs to the model, which estimated daily water temperatures at Bonneville Dam. The model used time lags between air temperature and water temperature to determine how the river's "memory," or capacitance, has changed over time. Since the 1850s, there has been an increase of 2.2 ± 0.2°C in mean annual water temperature in the lower Columbia River. The largest seasonal rate of increase of about 2.2 ± 0.2°C/century occurs in the fall and early winter while the smallest seasonal increase rate of about 0.04 ± 0.2°C/century occurs in the spring. Furthermore, I sought to identify and quantify the causes of these long-term changes by distinguishing what fraction of the water temperature changes were due to climate effects and how much of the changes were due to the reservoir system and irrigation withdrawals. I found the hydropower and reservoir system has contributed approximately twice as much as climate change to warming river temperatures. While these are simplified approximations of attribution, they have important implications for conservation management.

Rights

In Copyright. URI: http://rightsstatements.org/vocab/InC/1.0/ This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).

Persistent Identifier

https://archives.pdx.edu/ds/psu/34216

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