Rivers/Streams

Stream water quality

About this indicator: 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. From 2001 through 2005, 56 sites in the Lake Washington and Green-Duwamish drainage basins were sampled monthly for temperature, pH, fecal coliform bacteria and dissolved oxygen, relative to state standards.

Status: Overall stream water quality in King County is fairly good. Of the total sampled stream sites, 63 percent were considered moderate to high water quality, and 38 percent were rated to be of high concern. All sites rated of high concern were impacted in part by excessive nitrogen and/or phosphorus. In addition, low dissolved oxygen and high bacteria levels contributed to high concern ratings at 6 and 4 sites, respectively. None of the "high concern" sites were the result of high temperatures. While cumulative rainfall in 2006 was average compared to historical values, July and August were relatively dry months.

Influencing factors: Stormwater, 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, high temperatures (colder water holds more oxygen), and high levels of organic matter (bacteria use up oxygen in the process of decomposing).

Existing DNRP response: King County is responsible for preserving water quality and preventing and repairing damage to its waterways and water bodies. Attention is given to high concern sites to improve water quality. This can involve constructing or engineering a solution, identifying where or how pollutants are entering the stream, and/or educating adjacent property owners about the impacts of pesticides and fertilizers on streams.

Priority new actions: Results from King County's Water Quality Index highlight the need for a comprehensive and coordinated approach to resolving in-stream flow management, since lower flows inflate every water quality measurement of the index. King County will continue to advocate for water supply planning at a regional scale to gain a better understanding of the location, causes, effects and ways to mitigate impacts.

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Stream riparian habitat

About this environmental indicator
Increased population and development have substantially altered the landscape in King County over the past two centuries. This indicator reflects landscape changes that protect forest and aquatic habitats along streamside, or riparian, corridors.

Forest data were derived from a 2001 Landsat image, and impervious area data were derived from 2000 multispectral images. The width of riparian areas along stream banks varied between a minimum 165-foot buffer on each side and expanded to include wetland and steep slope areas. Possible landslide areas that extend past this buffer were also included. This approach to defining "riparian areas" is intended to encompass functional features of adjacent lands that could have been missed if a simple buffer width were used.

Status: Stream riparian land cover was categorized by urban vs. rural areas. Countywide, stream riparian areas in rural areas (71percent) have higher forest coverage than urban areas (39 percent), as shown in Chart 1 and Figure 1. Impervious coverage along the riparian corridor in urban areas (26 percent) was almost seven times more than in rural areas (4 percent).

Influencing factors: Forests naturally regulate stormwater runoff, protect water quality ,provide habitat for many species, and maintain healthy streams and rivers for salmon and other fish. Less forests result in less stormwater control, less habitat for forest species, and aquatic systems that are less-healthy for fish. Increases in impervious surfaces are generally associated with the highest rates of stormwater runoff, the highest degradation in water quality, and the most impacts on forest and aquatic species.

Existing DNRP response: Land-use regulations, which were updated as part of the Critical Areas Ordinance in 2004, attempt to maintain a minimum of 65 percent forest cover and limit impervious areas to less than 10 percent in rural, unincorporated King County. They also provide extra protection for aquatic riparian areas. King County DNRP intends to monitor forest cover and impervious area within riparian zones.

The county works with landowners to restore streamside parcels that have important benefits as aquatic resources. In addition, the King County Water and Land Resources Division's capital projects program builds small and large stream and wetland enhancement projects while protecting public safety. Habitat restoration projects include streamside and wetland planting and in-stream habitat improvements.

Priority new actions: King County is in the midst of updating its 30-year old Shoreline Master Program, which guides land-use activities along shorelines of marine areas and most lakes and streams in unincorporated King County. The first step in this effort is to review current shoreline conditions, including ecology, public access, land use and historic resources. The program update, which is expected to be completed in late 2008, will include changes that will have an effect on this indicator.

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Stream water quantity

About this indicator: This indicator uses a stream "flashiness" index The "flashiness" index is based on the reciprocal of the fraction of days during the year that the flow rises above the annual mean daily flow. Because peak stream flow rises and falls more quickly in urban areas than forested areas, urban streams tend to have a smaller fraction of days during the year when the flow is above the annual mean daily flow, and a higher "flashiness" index score. This increase in the "flashiness" index score represents the loss of water storage capability of soils and vegetation due to urbanization. To assess conditions throughout the county, the median stream "flashiness" is calculated each year across all streams where flow is measured. The median stream "flashiness" score represents the degree of water storage ability where half of the streams are flashier and half are less flashy.

Status: Flows from 17 stream sites in King County were measured and their "flashiness" calculated during the 2006 water year (October 2005 — September 2006). Flows for four of these streams were measured by the United States Geological Survey. The median of the "flashiness" index scores across all streams measured in King County has increased between 1945 and 2006 and was higher in 2006 than in 2005.

These data suggest that increased urbanization in King County has resulted in faster surface runoff and peak stream flow rise and fall than previously occurred for some of the streams

Influencing factors: Extensive development can substantially alter stream flow patterns and how they respond to rainfall. In urban areas, surface runoff occurs more quickly than in forested areas because less rainfall is absorbed by the vegetation and soil. Faster runoff in urban areas results in higher peak stream flows rising and falling more rapidly than under forested conditions. Increased peak flows and "flashiness" leads to the most obvious effects from a human perspective — flash flooding and channel erosion. From a biological perspective, streams with greater "flashiness" are disturbed more often. Organisms that survive in these conditions are those that have adapted to more frequent and severe disturbances.

Existing DNRP response: King County has a multitude of regulatory, educational, and on-the-ground programs to reduce the impacts of development on streams and reduce the amount of "flashiness." The County's Drainage Design Manual directs drainage requirements for all new development.

Priority new actions: In compliance with National Pollutant Discharge Elimination System permit requirements from the state (as part of the federal Clean Water Act), a closer linkage between the effectiveness of stormwater controls and water quality and flows is expected. This may translate into more monitoring at retention / detention ponds to make sure they are working as expected.

Instream flows
"Instream flows" calculates the quantity of water in streams needed to protect and preserve fish, wildlife and recreational activities. The term is most often used in formal legal documents, typically adopted state rules used to determine if water is available for new out-of-stream uses, to regulate those new uses, and to define the stream flows that need to be met in the stream. The Washington State Department of Ecology maintains a Web site with detailed descriptions, regulations, data, and links to further resources at http://www.ecy.wa.gov/programs/wr/instream-flows/isfhm.html. WRIA 7 is the only King County WRIA currently shown on the Web site (https://fortress.wa.gov/ecy/wrx/wrx/flows/irpp-wria.asp?id=07).

303(d) List
The state has assessed available water quality data to get a better picture of the overall status of water quality in Washington's waters. The results of the assessment are submitted to the Environmental Protection Agency (EPA) as an "integrated report" to satisfy federal Clean Water Act requirements of sections 303(d) and 305(b). The assessment includes the list of known polluted waters in the state, sometimes referred to as the 303(d) list. Background, resources, and information related to this list can be viewed on their Web site (http://www.ecy.wa.gov/programs/wq/links/wq_assessments.html). The state Web site also provides an interactive mapping and query tool that can be used to show water bodies listed under Section 303d of the Clean Water Act by the Washington Department of Ecology as violating clean water standards.

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