Accurate streamflow permanence classification that differentiates between perennial (year-round surface flow) and nonperennial (periodic stream drying) streams is important for a variety of land and water management decisions. Streamflow permanence refers to the capacity of watersheds and their stream channels to support surface flows continuously throughout the year.

The following data products were developed by USGS to help determine if a stream reach is perennial or nonperennial. You can now access these products in StreamStats:

1) Streamflow permanence probabilities (SPP) from the PRObability of Streamflow PERmanence (PROSPER) model (version 2.1) for the Pacific Northwest Region (Hydrologic Unit Code 17).

2) The hydrographic classification of the NHDPlus HR flowlines as perennial or non-perennial.

3) Binary field observations of streamflow.

Key product features

1) The PRObability of Streamflow PERmanence (PROSPER) model provides adjusted annual streamflow permanence probabilities (SPP). The SPP is the probability that a stream will have year-round flow, and is used to classify streams as perennial or non-perennial with additional qualifiers of more confident or less confident for each class based on the combined SPP and Standard Error values 2) The USGS incorporated stream classifications in USGS Topographic Maps which vary by the map resolution and the year the maps were published. These stream classifications were migrated into the USGS National Hydrography Dataset (NHD) and published with NHDPlus HR products (https://www.usgs.gov/national-hydrography/nhdplus-high-resolution). Jaeger and others (2025) combined stream classifications from the NHDPlusHR, topographic maps (1:24,000) publication year, and self-calibrating palmer drought severity index values, to provide users additional information to identify potential bias in the original topographic map stream classifications. The PROSPER application in StreamStats automatically selects the nearest stream reach and provides data from Jaeger and others (2025) for comparison of current PROSPER model outputs to original map classifications. 3) Field observations flow/no flow stream conditions that were collected with the FLOwPER mobile application may provide additional information or more recent streamflow conditions than modelled data. The three data products may be evaluated together to determine if existing information is sufficient or if additional information, including ground truthing, is needed. By comparing multiple pieces of information, users may gain a more holistic understanding of potential conditions at a given location.

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USGS Streamflow Permanence Research This update in StreamStats is part of the Streamflow Permanence in the Pacific Northwest project which is funded by USG Water Mission Area Water Budget Program. This project is part of a larger body of research on streamflow permanence in USGS. For more information about this research or to contact our team, please visit USGS Streamflow Permanence.