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What is Water Typing?

In 1975, the Washington Department of Natural Resources (WDNR) developed the process of water typing to regulate forest practices that impact Washington’s surface waters, classifying streams into one of five types depending on their physical, biological, and human-use characteristics. Fish-bearing stream reaches are classified as Type 1, 2, or 3 according to fish abundance and physical characteristics of the stream channel; Type-4 and Type-5 streams are considered non fish-bearing. Accurate water typing is essential to protecting fish and their habitats because Type classification dictates the proximity of allowable human activity to streams and other surface water. Riparian buffer zones required on Type-2 streams, for example, are broader than those required on Type-4 streams.


In 1997, WDNR revised its criteria for classifying streams as fish-bearing and upgraded protections for waters identified as non fish-bearing. In response to Forest and Fish policy, in 2005 WDNR modified the regulatory watertype maps to reflect the results of a logistical regression model that used multiple parameters (basin size, precipitation, gradient, etc.) to predict the distribution of fish habitat in watersheds.  The model was still based on the same (coarse) 10 meter DEM that existed prior to the modeling effort.  The modeled maps were again updated in October 2007; the most current WDNR regulatory watertype maps are available for review at WDNR’s Forest Practices Application Review System website.

However, because the current regulatory watertype maps demonstrably under-represent the upstream extent of fish and fish habitat, and many streams are mapped incorrectly or not at all, many streams are not receiving adequate protection from water quality degradation associated with adjacent land use practices. Hundreds of miles of wild salmon and trout habitat have been compromised because they were misidentified and subsequently subjected to inappropriate land practices.

Under its Habitat Lost & Found program, Wild Fish Conservancy has since 1994 been performing field surveys on streams throughout Washington to correct misclassifications and thereby qualify these water bodies for the protection warranted under existing laws. To date, Wild Fish Conservancy has upgraded the status of nearly 5,000 stream reaches statewide.

Washington’s water typing system is defined in Washington Administrative Code 222-16-031.  Changes to the system enacted in March 2005, including the introduction of new water type codes, are outlined at the WDNR Water Typing home page.

Crisis in Regulating Development

Though originally designed for regulating forest practices, the WDNR water typing maps and classification system have been widely adopted by city and county agencies for regulating development activities within local jurisdictions. Unfortunately, the maps have proven even more inaccurate outside the forest-practice zones. Recent water typing surveys by Wild Fish Conservancy in rural and suburban landscapes in King, Snohomish, Jefferson, San Juan, and Island counties documented comparable rates of error in the original designation of streams as fish-bearing or non fish-bearing, and provided evidence that a significant number of streams in these areas do not even appear on any maps.  Of 38.4 stream miles surveyed by Wild Fish Conservancy during summer 2002, some 17.7 miles or 46% were previously unrecorded on WDNR water type maps.

Since 1997 WDNR has maintained a system for correcting water type designations in forestlands, but there is no comparable system to ensure timely updates in non-forestry areas subject to Growth Management Act planning and regulations. In addition, county and local planning and conservation ordinances commonly rely on WDNR water type maps, often without adequate mechanisms for checking or correcting the data presented in the maps. These factors are creating a crisis in how development along streams is being regulated in Washington. Local jurisdictions are relying on inaccurate water typing maps to regulate land and water use, and many streams and the fish they support are facing threats from development and associated practices because they are not receiving protection they legally deserve under existing laws.

Wild Fish Conservancy submits all watertype assessment results to WDNR and affected local governments and Tribes so that the groundtruthed mapping information can be used to identify and protect sensitive stream environments.

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