Trends in summer low flow for the period 1975 to 2017 at gauging stations on the 12 large rivers described in the 2020 recovery target has varied from river to river. The majority of rivers without dams have been on a declining trend since the 1970s. Regulated rivers, expectedly, have had relatively stable or even increasing flows. Because the direction of the trends vary across rivers, we conclude that progress is “mixed”, with many river flows not yet meeting their expected 2020 target trends.
Patterns in the trends in summer low flows generally did not change much over the last few years and most are on the same trajectory. Most rivers with stable summer low flows a few years ago continue to have stable flows, rivers with decreasing trends continue to show decreasing trends, and rivers with increasing trends, continue to show increasing trends.
Stable flows in unregulated rivers that were stable in 2010: Puyallup (near Orting WA), Dungeness, and Nooksack rivers.
Stable Snohomish River summer flows.
Weak decreasing trend in summer low flows in the Deschutes River, North Fork Stillaguamish River, and Issaquah Creek.
Stable or increasing flows in highly regulated rivers: Nisqually, Cedar, Skokomish, Green, and Skagit.
Monitor low flow in the Elwha River after dam removal.