Most King County offices will be closed on Thursday and Friday, Nov. 23-24, 2017, for the Thanksgiving holiday.  
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Conventional, Nutrient and Bacteria charts illustrate results from monthly stream and river monitoring during the current year. Water samples collected under both baseflow and wet weather/storm flow conditions are included in these charts.

Where applicable, data are compared with water quality criteria established by the Washington State Department of Ecology (WDOE) in the Washington Administrative Code [WAC] 173-201A. For more information about these criteria, visit WDOE's Web site.

For most sites data collection began in the 1970s. The period of record for each site is shown on the Stream and Rivers Ambient Monitoring Sites Table. Historical data for this site are represented by box plots (see explanation below).

Box Plots Explained

We are using boxplots to display monthly historical data. Box plots, or box and whisker plots, succinctly summarize the median, upper and lower quartiles, and minimum and maximum values.

Interpreting a Boxplot

The box contains the middle 50% of the data. The upper edge (hinge) of the box indicates the 75th percentile of the data set, the lower hinge indicates the 25th percentile. The difference between the values of the hinges is called the interquartile range. The line in the box indicates the median value of the data set. The ends of the vertical lines (whiskers) extend to 1.5 times the interquartile range. Values that lie out side of the whiskers are termed outliers. Outliers can be viewed or hidden by checking/unchecking the outlier box.

For more information about archived data , please contact Debra Bouchard at debra.bouchard@kingcounty.gov.