A multidecadal oscillation in summer low flows is revealed in Puget Sound streams
Streaming Media
Presentation Abstract
In Pacific Northwest streams, summer low flows severely limit water available to competing instream (salmon) and out-of-stream (human) uses, creating broad interest in how and why low flows are trending. Analyses that admit only linear (monotonic) trends have showed that flows in minimally-disturbed streams across the PNW declined between 1948-2013. Such consistent declines over such a large region implicate remote climatic drivers as influencing flow trends in all streams. In this analysis of flow trends in minimally-disturbed streams, monotonic change was not assumed, rather, trends were modeled using polynomials. A multidecadal oscillation was revealed in low flows, increasing from the 1930s until the 1950s, then declining until the 1990s, when a second inflexion was detected. The decline is consistent with previous results that support widely-held perceptions of monotonically declining low flows over recent decades. But the recent upturn is not widely recognized. A similar oscillation was detected in precipitation, and opposing oscillations in temperature, Pacific Decadal Oscillation, and Interdecadal Pacific Oscillation series. Multidecadal oscillations with similar periods to those detected in this analysis are well known in climate indices and their proxies, yet an expectation that flows should oscillate over multidecadal spans is not prevalent. Results 1) establish a reference set of flow trends in ‘minimally-disturbed’ streams of the Puget Sound region for comparison with trends in streams that are subject to disturbance by local human factors, such as groundwater abstraction via wells; 2) suggest that anthropogenic warming is not the only factor driving trends in flows, or even the dominant factor, else there would have been no recent inflexion in flows.
Session Title
Poster Session 2: The Salish Sea Food Web and Cycles of Life
Conference Track
SSE14: Posters
Conference Name
Salish Sea Ecosystem Conference (2022 : Online)
Document Type
Event
SSEC Identifier
SSE-posters-11
Start Date
26-4-2022 4:30 PM
End Date
26-4-2022 5:00 PM
Type of Presentation
Poster
Genre/Form
conference proceedings; presentations (communicative events); posters
Subjects – Topical (LCSH)
Streamflow--Washington (State)--Puget Sound; Streams--Washington (State)--Puget Sound
Geographic Coverage
Puget Sound (Wash.)
Rights
Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this document for commercial purposes, or for financial gain, shall not be allowed without the author's written permission.
Type
Text
Language
English
Format
application/pdf
A multidecadal oscillation in summer low flows is revealed in Puget Sound streams
In Pacific Northwest streams, summer low flows severely limit water available to competing instream (salmon) and out-of-stream (human) uses, creating broad interest in how and why low flows are trending. Analyses that admit only linear (monotonic) trends have showed that flows in minimally-disturbed streams across the PNW declined between 1948-2013. Such consistent declines over such a large region implicate remote climatic drivers as influencing flow trends in all streams. In this analysis of flow trends in minimally-disturbed streams, monotonic change was not assumed, rather, trends were modeled using polynomials. A multidecadal oscillation was revealed in low flows, increasing from the 1930s until the 1950s, then declining until the 1990s, when a second inflexion was detected. The decline is consistent with previous results that support widely-held perceptions of monotonically declining low flows over recent decades. But the recent upturn is not widely recognized. A similar oscillation was detected in precipitation, and opposing oscillations in temperature, Pacific Decadal Oscillation, and Interdecadal Pacific Oscillation series. Multidecadal oscillations with similar periods to those detected in this analysis are well known in climate indices and their proxies, yet an expectation that flows should oscillate over multidecadal spans is not prevalent. Results 1) establish a reference set of flow trends in ‘minimally-disturbed’ streams of the Puget Sound region for comparison with trends in streams that are subject to disturbance by local human factors, such as groundwater abstraction via wells; 2) suggest that anthropogenic warming is not the only factor driving trends in flows, or even the dominant factor, else there would have been no recent inflexion in flows.
