Figure 1: Streams Water Quality Index

Figure 2: Number of Pesticides in King County Streams

Figures:  
• Figure 1: Streams Water Quality Index  – 
• Figure 2: Number of Pesticides in King County Streams

Data Discussion

The Indicator Defined

King County's Water Quality Index is derived from three main groupings of results describing the conditions of rivers and streams, groundwater and lakes. King County's Water Quality Index integrates key factors into a single number that can be compared over time and across locations. This index is based on the Oregon Water Quality Index and work done by the Washington Department of Ecology.

Data Interpretation/Evaluation

The impacts of development, landowner practices in areas close to the shoreline and pollutants are the dominant drivers determining the health of freshwater bodies in King County. Less forest cover and increases in impervious surfaces result in higher stream temperatures and more urban runoff. Phosphorus from blended stormwater and wastewater that bypasses the treatment process during significant storm events, failing septic systems, pet wastes and water bird droppings reduce dissolved oxygen levels and increase water temperatures.

Rivers and Streams

Overall stream water quality in King County is impacted by increased development in our region — primarily stormwater runoff. In 2006-07, cumulative rainfall was well above average compared to historical values, in part due to a very wet November and December.

Stormwater, combined sewer overflows (CSO's), waterfowl and pet wastes are the most likely sources of bacteria in urban streams. Poor livestock manure management and failing septic systems can be a potential source of bacteria in agricultural and suburban areas. In wetlands, wildlife excrement and stagnant water conditions can lead to elevated bacteria counts. High phosphorus concentrations are found in fecal material and elevated concentrations are often linked to similar sources as bacteria. In addition, elevated phosphorus concentrations are linked to areas undergoing development.

Low dissolved oxygen concentrations can be associated with low flows, wetlands, high temperatures (colder water holds more oxygen), and high levels of organic matter (bacteria use up oxygen in the process of decomposing).

From 2000 through 2007, 56 sites in the Lake Washington and Green-Duwamish drainage basins were sampled monthly for temperature, pH, fecal coliform bacteria, dissolved oxygen, turbidity, total suspended solids, and nutrients (phosphorus and nitrogen) relative to state standards and guidelines.

Of the total sampled stream sites in King County in 2006-07, 45 percent were considered moderate to high water quality, and 55 percent were rated to be of high concern. (Figures 1 and 3) All sites rated of high concern were impacted in part by excessive nitrogen and/or phosphorus. In addition almost all high concern sites were affected by high fecal coliform bacteria (97 percent), low dissolved oxygen (74 percent), high temperatures (58 percent), and high-suspended solids/turbidity (32 percent).

In 1999, the U.S. Geological Survey conducted a study on pesticides in twelve urban streams and discovered Juanita Beach to have the highest number of pesticide compounds (Meydenbauer Bay Beach was not tested during this study).(Figure 2) Pesticides adversely affect aquatic wildlife and human health. They can affect the reproductive and endocrine systems of both humans and salmon. Of the compounds detected, herbicides were the most commonly found, typically making up more than 60% of the compounds. Transformation products are broken down pesticides. Pesticides sold for residential use were found to be a major likely source of the pesticides in the streams.

Lakes

The people of King County have made significant investments in water quality improvement and protection to lakes Washington, Sammamish and Union beginning with the diversion of wastewater effluent out of Lake Washington and Lake Sammamish in 1968.

Water quality improvements continue with efforts to:
* Reduce the discharge of combined sewer overflows
* Improve King County's wastewater treatment system (including construction of Brightwater treatment facility)
* Expand effluent reuse programs

These gains in water quality are constantly threatened by increasing amounts of phosphorus entering the watersheds as a result of increased development. In this region, high concentrations of the nutrient phosphorus are often correlated with increased algal growth. Thus, if the amount of phosphorus entering lakes is controlled or reduced, algal blooms are likely to decrease. Algal blooms are a nuisance because they can cause scum to form on the lake's surface and occasionally give a foul odor and taste to the water. When a bloom dies off it can also deplete the oxygen levels available to other aquatic life. In rare circumstances, algal blooms can become toxic.

This indicator uses summer phosphorus concentrations converted to Trophic State Indicators (TSI-TP) to assess conditions. Trophic State Indicators relate phosphorus to the amount of algae that the lake can support. Values below 50 have low or moderate potential for nuisance algae blooms; values above 50 have a higher potential. Slightly more than 80 percent of small lakes have good water quality with low potential for nuisance algal blooms. (Figure 4)

Lake water quality results vary annually, depending on the climate and biological interactions that combine to create unique annual conditions in each lake. For example, the 1994-2007 results for Lakes Sammamish and Washington show phosphorus concentrations fluctuated between low to moderate threshold from year to year, indicating water quality varies from good to moderate with low potential for nuisance algal blooms. (Figure 5) Lake Union typically has phosphorus concentrations within the moderate water quality range, with the exception of 2007. In 2007 high phosphorus levels put Lake Union in the poor water quality range.

Lake Sammamish is the only one of the three large lakes with a management plan and designated water quality goals. The plan calls for an annual volume weighted total phosphorus concentration (VWTP) of 22 µg/L or less. Both the north and south lake stations met this goal in 2007 with a VWTP of 19 µg/L and 18 µg/L, respectively.

100 percent of the Lake Sammamish stations, 85 percent of Lake Washington stations, and 60 percent of Lake Union stations have achieved the lake standard for fecal coliform bacteria, even though this measurement uses a standard that is exceptionally difficult to attain.

Groundwater

King County has been tracking groundwater quality on Vashon-Maury Island since 2001. Nitrate is used to track groundwater quality because it is a good indicator of changes caused by human activities, such as land-use development. King County's goal is to ensure high water quality through effective land-use and on-site septic regulations.

The groundwater quality indicator uses a nitrate index, defined as the maximum concentration of the annual sampling results divided by the maximum contaminant level (MCL) of Nitrate (10 mg/L). This method yields one number. The closer this index gets to 1 (or over 1) the greater concern. The nitrate index has been less than 0.5 since 2003.

Of the 19 well/spring sites monitored, all have tested below the drinking water standard (Maximum Contaminant Level, MCL of 10 mg/L) and all have less than 5 mg per liter of nitrate present. Less than half the sites tested have seen above average nitrate increases since testing began.

Data Source and Limitations

The data source for Figures 1, 3, 4 and 5 comes from the King County DNRP/WLRD Science, Monitoring and Data Management Section (http://dnr.metrokc.gov/wlr/waterres/streamsdata/). This water quality index generates a number ranging from 10 to 100. Higher numbers reflect better water quality. The index uses data for temperature, pH, fecal coliform bacteria and dissolved oxygen, relative to state standards required to maintain beneficial uses. For nutrient and sediment measures, where the state standards are not specific, results are expressed relative to expected conditions in a given eco-region. The multiple water quality parameters are combined and results aggregated over the water year to produce a single score for each sample station. In general, stations scoring 80 and above meet expectations and are of "low concern," scores 40 to 80 indicate "moderate concern," and water quality at stations with scores below 40 do not meet expectations and are of "high concern." 56 stations are monitored monthly. Data can be downloaded from http://dnr.metrokc.gov/wlr/waterres/streamsdata/.

Data related to Figure 2 and the discussion of pesticide quantities in streams was contributed by Communities Count (www.communitiescount.org).  The original data source is from Pesticides Detected in Urban Streams in King County, Washington, 1998-2003. Lonna Frans from the U.S. Geological Survey provided the figure on pesticides in urban streams.

Limitations to this data include a lack of data prior to 1996. In addition, information on the cause of fecal coliform is not recorded. Finally, there are not consistent standards among local health departments for closing beaches due to pollution.

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