Aquatic Ecosystems: Current Research
Modeling Climate Change and Land Use Impacts on Salmon Recovery in the Snohomish River Basin
- Richard Palmer, CIG and UW Civil Engineering (contact person)
- Matthew Wiley, CIG and UW Civil Engineering
- Elizabeth Korb, CIG and UW Civil Engineering
- James Battin, NOAA Northwest Fisheries Science Center
- Mary Ruckelshaus, NOAA Northwest Fisheries Science Center
- Krista Bartz, NOAA Northwest Fisheries Science Center
- Hiroo Imaki, NOAA Northwest Fisheries Science Center
The federal listing of Puget Sound Chinook salmon and bull trout as threatened species under the Endangered Species Act has led to greater efforts to restore salmon populations in the heavily populated Puget Sound region. Climate change may impact the effectiveness of these salmon recovery efforts as warmer temperatures bring:
- more rain and less snow to the region's mountains (increasing the risk to salmonid eggs from streambed scouring);
- earlier and lower peak spring runoff (potentially affecting the timing of juvenile salmon out-migration);
- lower and warmer summer streamflows (reducing available spawning habitat and increasing the potential for lethal summer water temperatures); and
- higher fall flows (also increasing the risk of streambed scouring).
Changes in land use and stream habitat are also likely to have important impacts on recovery efforts.
An innovative collaboration between NOAA's Northwest Fisheries Science Center (NWFSC), the Climate Impacts Group (CIG), and the University of Washington's (UW) Water Resources Management and Drought Planning Group evaluates the effects of future climate change and changes in large scale land use on Chinook salmon in the Snohomish River basin (figure 1). The Snohomish River basin is the second largest river basin in Puget Sound and home to two distinct populations of spawning Chinook salmon: Skykomish Chinook and Snoqualmie Chinook. Both populations have declined to less than 10% of historic population levels.
click image to enlarge
Figure 1 Map of the Snohomish Basin, Washington as modeled in the DHSVM hydrology model. Urbanized areas linking the modeled portion of the basin to Puget Sound (northwest corner of the basin) are not shown in this figure.
In June 2005, members of the Snohomish Basin Salmon Recovery Forum approved a $133.7 million salmon recovery plan that will guide salmon recovery activities in the basin. The recovery plan estimates the effects of habitat condition and functioning, hatchery and harvest management, interactions with other species, and other environmental factors on salmon populations over the next 50 years. An evaluation of climate and land use change impacts on the plan's recovery objectives is critical given the basin's potential sensitivity to climate impacts, the plan's 50 year planning horizon, and the plan's financial impact.
The Snohomish basin study uses changes in temperature and precipitation derived from the GFDL and Hadley Centre climate models to project shifts in streamflow and water temperature in the years 2025 and 2050. The study also accounts for the recovery plan's planned changes in land cover and land use. The outputs from the hydrology and water quality model serve as inputs into the SHIRAZ salmon life cycle model, a population model created by Ray Hilborn at the UW's School of Aquatic and Fisheries Sciences that has been modified by NOAA for this study. The SHIRAZ model uses information on water, temperature, flow, and sediment (among other factors) to assess how Chinook salmon might respond to the altered conditions.
The hydrologic models and statistical analyses of model outputs are aimed at addressing the following questions:
- How do alternative assumptions about future climate and land use conditions affect hydrology and temperature in Pacific Northwest watersheds?
- How do alternative assumptions about future climate and land use conditions affect predictions of fish-habitat dynamic models?
- How robust are the alternative sets of habitat recovery actions to assumptions about future conditions (e.g., climate change, human population growth, ocean conditions)? To alternative modeling approaches?
The study is funded by NOAA's NWFSC and conducted by the NWFSC, the CIG, and the University of Washington's Water Resources Management and Drought Planning Group.
- Snohomish Basin Salmon Conservation Plan
- UW Snohomish project web site
- Presentation by Matt Wiley and Rick Palmer on preliminary results of the study
For publications on the Climate Impacts Group’s (CIG) research on climate and aquatic ecosystems, please see CIG Publications.