NW CASC Research Provides New Datasets on Streamflow Permanence in Northwest

What does increasing drought mean for the Northwest streams that provide critical habitat for our region’s fish and wildlife? As the climate changes, which streams will continue to flow year-round and which will dry up? Natural resource managers use information about streamflow permanence, or the extent to which streams maintain flowing surface water, to make decisions about managing streams and the fish and wildlife that depend on them.

Streams are classified based on whether they flow year-round (perennial) or for only part of the year (intermittent and ephemeral). These classifications are important because perennial streams receive special regulatory protections for providing critical fish and wildlife habitat. However, many existing stream classifications are inaccurate and outdated, lacking consideration of how land use change has already altered streamflow or of how climate change is likely to impact streamflow.

To address this knowledge gap, the Northwest Climate Adaptation Science Center (NW CASC) funded researchers to develop new streamflow permanence information at regional scales that account for year-to-year variations in climatic conditions. The goal of this research was to improve land managers’ ability to identify headwater streams resilient to drought conditions, enabling them to focus limited resources on watersheds that provide critical habitat for threatened aquatic species.

This research paired existing streamflow permanence observations (about 25,000) from federal and state agencies across the Pacific Northwest with modeling to allow analysis of streamflow permanence at a regional scale, resulting in the PRObability of Streamflow PERmanence (PROSPER) model. The PROSPER model includes publicly available regional datasets, models and maps of where perennial streams are located across the Pacific Northwest and how they respond to year-to-year variation in climate conditions such as annual snow and rainfall. It provides streamflow permanence information for the Northwest at an unprecedented spatial scale (30 m channel segments) and temporal resolution (annual). PROSPER model predictions of streamflow permanence are now publicly available through the USGS StreamStats platform, and a recently published paper introduces the PROSPER model and demonstrates its use by analyzing streamflow permanence in three Northwest river basins.

Throughout this project, researchers engaged representatives from tribal, state, federal and non-governmental institutions across the Northwest to gather feedback on project objectives, methods, products and data delivery. Engaging managers throughout the project helps ensure that the products can be used to help managers better understand drought vulnerability and focus limited conservation resources on watersheds that provide crucial habitat for fish and wildlife.

Read the Paper

Check out the Streamflow Permanence Observations

Olympic National Park, Port Angeles, WA
Source: Jachan DeVol, Unsplash, Public Domain