Estimating river flows across basins using water isotopes

Transcription

1 Western Washington University Western CEDAR Salish Sea Ecosystem Conference 2018 Salish Sea Ecosystem Conference (Seattle, Wash.) Apr 4th, 2:00 PM - 2:15 PM Estimating river flows across basins using water isotopes Lillian McGill Univ. of Washington, United States, lmcgill@uw.edu Ashley E. Steel U.S. Forest Service, United States, asteel@fs.fed.us Renee J. Brooks U.S. Environmental Protection Agency, United States, brooks.reneej@epa.gov Follow this and additional works at: Part of the Fresh Water Studies Commons, Marine Biology Commons, Natural Resources and Conservation Commons, and the Terrestrial and Aquatic Ecology Commons McGill, Lillian; Steel, Ashley E.; and Brooks, Renee J., "Estimating river flows across basins using water isotopes" (2018). Salish Sea Ecosystem Conference This Event is brought to you for free and open access by the Conferences and Events at Western CEDAR. It has been accepted for inclusion in Salish Sea Ecosystem Conference by an authorized administrator of Western CEDAR. For more information, please contact westerncedar@wwu.edu.

2 Where does the water come from? Examining water stable isotopes across river basins Lillian McGill 1, E. Ashley Steel 2, and J. Renée Brooks 3 1 University of Washington 2 PNW Research Station, USDA Forest Service 3 Western Ecology Division, US EPA

3 What can we learn from a water sample?

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7 Water isotopes are naturally occurring, and partitioned by hydrologic fluxes Isotopes have different weights. This causes fractionation due to phase changes. Fractionation causes spatial variation in the isotope composition of precipitation. As you move inland from the coast and up in elevation, the isotopic signature becomes more negative.

8 Streams integrate the isotopic signal of precipitation Time and Space Time, Space, Substrate Source: Precipitation (systematically variable) Processes: Mixing Collection Point: Reflects hydrologic mixture of sources

9 WHERE can we use water isotopes to understand water sources across rivers?

10 Samples collected in four river basins within Washington Wenatchee Washington, USA Skagit Snoqualmie Green

11 Westside basins display strong relationships with elevation, the Wenatchee does not

12 River basins have many landscape features that influence our ability to use the rainout effect as a tool for tracing water source. Snoqualmie Green Skagit Wenatchee

13 HOW can we use water isotopes to understand water sources across rivers?

14 Samples collected at 46 monitoring sites within the Snoqualmie River Basin

15 Samples collected across five hydrologic periods

16 Samples collected across five hydrologic periods: Early and late summer analyzed

17 Elevation drives isotopic signature. Tributaries have fairly stable isotopic signatures through time.

18 Elevation drives isotopic signature. Tributaries have fairly stable isotopic signatures through time.

19 Lower δδ 18 O values in June indicate higher elevation source water, presumably from residual snowmelt δδ 18 O June δδ 18 O September

20 Lower δδ 18 O values in June indicate higher elevation source water, presumably from residual snowmelt δδ 18 O June δδ 18 O September Outlet δδ 18 O: Avg. elevation: 8306 m Outlet δδ 18 O: Avg. elevation: 7648 m

21 Next Steps Continue to monitor and analyze Snoqualmie River stable isotopes Use a mixing model framework to predict how much water derives from the snow zone, rain-on-snow zone, and rain zone. Integrate water source estimates with climate projections for the basin to determine how future flows may shift.

22 Acknowledgements E. Ashley Steel, USDA Forest Service J. Renée Brooks, US Environmental Protection Agency Aimee Fullerton, National Oceanic and Atmospheric Administration This research was supported by a Department of the Interior Northwest Climate Adaptation Science Center graduate fellowship awarded to Lillian McGill. US DOI s Northwest Climate Adaptation Science Center USDA Forest Service s Pacific Northwest Research Station US Environmental Protection Agency s Western Ecology Division NOAA s Northwest Fisheries Science Center

23 Water isotopes are naturally occurring, and partitioned by hydrologic fluxes GMWL: δ 2 H = 8δ 18 O +10

24 Water isotopes are naturally occurring, and partitioned by hydrologic fluxes GMWL: δ 2 H = 8δ 18 O +10 Cloud Vapor

25 Water isotopes are naturally occurring, and partitioned by hydrologic fluxes GMWL: δ 2 H = 8δ 18 O +10 Precipitation Cloud Vapor

26 Water isotopes are naturally occurring, and partitioned by hydrologic fluxes GMWL: δ 2 H = 8δ 18 O +10 Precipitation Cloud Vapor New Cloud Vapor

27 Lower δδ 18 O values in June indicate higher elevation source water, presumably from residual snowmelt δδ 18 O June δδ 18 O September Outlet δδ 18 O: Avg. elevation: 8306 m Outlet δδ 18 O: Avg. elevation: 7648 m