Date of Award

8-18-2017

Document Type

Thesis

Department

Civil and Environmental Engineering

First Advisor

Stefan A. Talke

Subjects

Hydrology -- Oregon -- Columbia River, Water temperature -- Columbia River, Streamflow -- Columbia River, Anadromous fishes, Pacific salmon -- Effect of water temperature on

Subject Categories

Environmental Engineering | Water Resource Management

DOI

10.15760/honors.482

Abstract

The Columbia River is home to anadromous salmon populations that migrate upriver every year to spawn. These fish require cool water temperatures (Tw) to survive. In recent years, high summer Tw in the Columbia River has caused increased mortality of salmon. Different possible explanations for increased Tw include climate change, deforestation, and decreased summertime streamflow (Q) due to dams. In this study, robust linear regression models of Tw based on air temperature (Ta) and Q were developed to examine the change in Tw over time. The data was separated into an historical period (1938-1956) and a modern period (1977-2003). Seasonal regression models were used for May through October (summer) and November through April (winter) for each period. Comparison of these models showed that Tw has become less sensitive to recent atmospheric heating and cooling. By contrast, analysis suggested that Tw has become more sensitive to variations in Q. Of the 1.5ºC increase in maximum summertime Tw, approximately 1.3ºC was due to dams and reservoir management based on changes in regression coefficients and average Q. A smaller, 0.2ºC change was estimated to be caused by increasing Ta since the mid-20th century. While average maximum Tw has increased, both the statistical model and data suggest that the variability in Tw from its climatological average has decreased, probably due to reservoir management.

Comments

A thesis submitted in partial fulfillment of the requirement for the degree of Bachelor of Science in Civil and Environmental Engineering

Persistent Identifier

http://archives.pdx.edu/ds/psu/22528

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