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Water Quality Program

2014 Water Quality Assessment and 303(d) List for Washington State
Using Fresh Water Data

Washington Submits 2014 Water Quality Assessment to EPA

View the 2014 Assessment:

Changing to a Water-based Segmentation System for this Assessment

New with this Assessment, we are updating how we map polluted rivers, lakes and streams. We are moving from a land-based segmentation system (township/range/section) to a water-based (National Hydrography Layer) system. The mapping change helps us be consistent with other agencies and states, and is strongly recommended by the Environmental Protection Agency. To help visually explain the differences between the land-based stream segments used in the 2012 Assessment with the water-based stream segments used in the 2015 Proposed Assessment, we have created printable posters: To assist with visually comparing the current 2012 Assessment listed segment with the proposed 2015 listed segment, we are providing a comparison tool on the map viewer. For step-by-step instructions on how to use this review tool, go to:

Frequently Asked Questions

(click each question for more information)

Why are we changing the segmentation system for the Water Quality Assessment?

What segment system has been used in past Assessments?

What are the benefits of using the NHD water-based system?

How are Assessment units represented for large rivers like the Columbia and Snake that are currently gridded?

How are the new NHD water-based segments different from the previous segment system?

What does the change in segmentation system means for permitted dischargers?

How are the new segments defined?

How can I compare the new segmentation system with the T/R/S segment system that is currently being used?

For questions about the water quality assessment process, please contact:

Patrick Lizon
Water Quality Program
Washington State Department of Ecology
P.O. Box 47600
Olympia, WA 98504-7600
Phone: 360-407-6782
E-mail: 303d@ecy.wa.gov


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Last updated August 2016