The summer low flow indicator measures current conditions and long-term trends in stream flows that occur during summer months when there is less rain and temperatures are warmer. The indicator tells us how often summer flows are below normal, relative to a 50-year baseline, in unregulated streams and rivers across Puget Sound. When flows are below normal, less water is available for people and wildlife to use, less habitat is available for salmon and it can contribute to increased water temperatures and lower water quality.
Status of annual summer low flow at indicator streamgages. Each cell is color coded for a category of frequency of below normal flow. Categories are based on the percent of days each year between July 15th and September 15th where the mean daily flow was below normal (i.e., below the 1948-1998 baseline 25th percentile). When most days (50% or more) were below normal, the cell is shaded purple. When fewer than 50% of the days were below normal, the cell is shaded blue. Streamgages are grouped as 1) rain-sourced, 2) transitional (between rain- and snow-sourced), or 3) snow-sourced based on the center of timing date.
No targets are currently set for this indicator.