Description: This whole-stream routed hydrography layer serves as the base hydrography for the StreamNet project's Linear Referencing System (LRS). StreamNet uses this layer to reference fisheries and aquatic related data compiled across the Pacific Northwest Region. Routes are based on whole streams uniquely identified via the LocationID (LLID) attribute. The route system is measured in feet to the nearest integer. To distinguish this hydrography layer from previously used systems, StreamNet refers to it as Mixed-Scale Hydrography - version 4.1, or "MSHv4.1". At version 1: This dataset includes all routed streams present in the PNW River Reach Files (PNWRF3), StreamNet's original 1:100k base hydrography layer. In addition, those features within the state of Washington are depicted at a higher resolution (1:24k scale or finer) and densified to include all named streams present in and sourced from Washington Department of Fish and Wildlife's 1:24k+ hydrography layer along with additional unnamed streams from that source where fish data exists and is compiled across the region. At MSHv1, the extent of StreamNet's regional hydrography was expanded and integrated with the 1:100k scale routed hydrography for California (CalHydro). While the StreamNet project does not manage fish data for California, the integration of California hydrography facilitates collaboration with StreamNet's partner project, "CalFISH". For more information about the CalFISH project, visit http://www.CalFISH.org At version 2: All features within the state of Oregon are now also depicted at the higher resolution (1:24k+) based on linework provided by Oregon Department of Fish and Wildlife and originally sourced from the Pacific Northwest Hydrography Framework (PNWHF) dataset. For the most part, linework from this source is coincident with the High-Resolution (24k+) National Hydrography Dataset (HR-NHD). Version 4 and minor releases primarily capture additional streams as needed to reference fish data submitted by partners. In addition stream routes from the British Columbia portion of the Columbia River Basin have been added at this version. Future versions of this dataset will incorporate higher resolution source linework within the states of Idaho and Montana with a trend toward using linework that is essentially coincident with that found in the HR-NHD. For more information about the source data contributing to this dataset, see the entity attribute and lineage sections of this metadata record. For more information about the StreamNet Project, see the supplemental information section of this metadata record or visit http://www.StreamNet.org