Presentation Abstract
Global warming is expected to dramatically alter the timing and quantity of water within the nation’s river systems; however, these impacts will be heterogeneous both within river basins and across regions. A detailed understanding of the spatial and temporal dynamics of water sources across river networks is therefore central to managing the impacts of climate change. Stable isotopes of water (2H:1H & 18O:16O) provide an emerging method for elucidating the contributions of varying water sources to rivers. Because the stable isotope composition of precipitation varies geographically, variation in the stable isotope composition of river water indicates the volume-weighted integration of source water within the watershed. During September 2017, we collected stable isotope samples across five river networks in the Pacific Northwest and SE Alaska that span a range of hydraulic and climatic conditions: the Snoqualmie, Green, Wenatchee, and Skagit Rivers as well as Cowee Creek. For each basin we regressed isotope values against computed spatial covariates such as elevation, mean annual precipitation, and geology to determine which covariates explained the greatest proportion of isotopic variation. We compared best-fit models for each basin to examine how major correlates of isotopic variation differed among river networks. Results indicate that rivers on the west side of the Cascades display a far stronger relationship to elevation than the Wenatchee. We then built spatial stream network models to display and communicate spatial patterns of isotopic variation within the Snoqualmie and Wenatchee basins. We also employed a mixing-model approach to determine where sources of water in the mainstems of each river originated (e.g. snow zone, rain-on-snow zone, or rain) during summer low flow conditions. Our results can be used by managers and watershed groups to estimate how river flows may shift in a changing climate.
Session Title
Water Quality and Hydrodynamics
Keywords
Stable isotope, Water source, Rivers
Conference Track
SSE1: Habitat Restoration and Protection
Conference Name
Salish Sea Ecosystem Conference (2018 : Seattle, Wash.)
Document Type
Event
SSEC Identifier
SSE1-231
Start Date
4-4-2018 2:00 PM
End Date
4-4-2018 2:15 PM
Type of Presentation
Oral
Genre/Form
presentations (communicative events)
Contributing Repository
Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.
Subjects – Topical (LCSH)
Water-supply--Effect of global warming on--Northwest, Pacific; Stable isotopes
Geographic Coverage
Northwest, Pacific; Salish Sea (B.C. and Wash.)
Rights
This resource is displayed for educational purposes only and may be subject to U.S. and international copyright laws. For more information about rights or obtaining copies of this resource, please contact University Archives, Heritage Resources, Western Libraries, Western Washington University, Bellingham, WA 98225-9103, USA (360-650-7534; heritage.resources@wwu.edu) and refer to the collection name and identifier. Any materials cited must be attributed to the Salish Sea Ecosystem Conference Records, University Archives, Heritage Resources, Western Libraries, Western Washington University.
Type
Text
Language
English
Format
application/pdf
Included in
Fresh Water Studies Commons, Marine Biology Commons, Natural Resources and Conservation Commons, Terrestrial and Aquatic Ecology Commons
Estimating river flows across basins using water isotopes
Global warming is expected to dramatically alter the timing and quantity of water within the nation’s river systems; however, these impacts will be heterogeneous both within river basins and across regions. A detailed understanding of the spatial and temporal dynamics of water sources across river networks is therefore central to managing the impacts of climate change. Stable isotopes of water (2H:1H & 18O:16O) provide an emerging method for elucidating the contributions of varying water sources to rivers. Because the stable isotope composition of precipitation varies geographically, variation in the stable isotope composition of river water indicates the volume-weighted integration of source water within the watershed. During September 2017, we collected stable isotope samples across five river networks in the Pacific Northwest and SE Alaska that span a range of hydraulic and climatic conditions: the Snoqualmie, Green, Wenatchee, and Skagit Rivers as well as Cowee Creek. For each basin we regressed isotope values against computed spatial covariates such as elevation, mean annual precipitation, and geology to determine which covariates explained the greatest proportion of isotopic variation. We compared best-fit models for each basin to examine how major correlates of isotopic variation differed among river networks. Results indicate that rivers on the west side of the Cascades display a far stronger relationship to elevation than the Wenatchee. We then built spatial stream network models to display and communicate spatial patterns of isotopic variation within the Snoqualmie and Wenatchee basins. We also employed a mixing-model approach to determine where sources of water in the mainstems of each river originated (e.g. snow zone, rain-on-snow zone, or rain) during summer low flow conditions. Our results can be used by managers and watershed groups to estimate how river flows may shift in a changing climate.
