Chinook in the Patagonia region have a much more diverse genetic ancestry than just "Kalama and Cowlitz springer runs". This 2017 report states that "Patagonian Chinook clearly had a diverse and heterogeneous ancestry". It does state though that West Cascades springs (ie Cowlitz) contributed substantially to the populations in the southern river basins. It is a hodgepodge of genotypes showing up besides Cowlitz springs that included Willamette springs, West Cascade falls (Bonneville, Cowlitz) and of course Soos Creek (Green/Duwamish). It was mostly Washington and Oregon stocks.

https://www.nature.com/articles/s41598-017-14465-y