More floods in the winter and lower flows in the summer mean that salmon on the Calawah River are having a harder time.
Lower flows in the summer lead to high temperatures that likely kill juvenile salmon before they can leave for the ocean and adult salmon before they can spawn. Higher flows in the winter destroy redds (egg nests) and harm juvenile salmon.
This is what salmon face in the Calawah River, where the Quileute Tribe reports decreasing summer flows and increasing flows during the rainy winters. This finding is reported in the State of Our Watersheds Report, recently released by the treaty tribes in western Washington.
Since 2010, streamflows for the Calawah River have followed the same overall trends as the previous 35 years – increasing peak flows and decreasing low flows. Such a scenario is predicted to occur as a result of climate change, and both trends could threaten salmon habitat and other aquatic ecosystem functions.
This change in flows can have real impacts on salmon survival:
Increased peak flows may also be the result of removal of vegetation. They cause the scouring of streambeds, channel incision (and subsequent disconnection from floodplain), and downstream transport of wood, resulting in simplified stream channels and greater instability. The trend of increasing peak flows has been shown to make streams less productive.
Many studies in the Pacific Northwest have documented the relationship between low streamflows and poor salmonid survival. The reduction in streamflows may result in less fish habitat because of dry streambeds or pools become cut off from the main channel and strand fish.