A Regional Stream Temperature Model to Aid Climate Vulnerability Assessments

Temperature in aquatic ecosystems is a fundamentally important property that dozens of resource agencies across the Northwest routinely monitor. Significant amounts of stream temperature data have been collected during the last two decades, but strategic coordination of these collection efforts within and among agencies is lacking and many redundancies exist. Moreover, legislative mandates to maintain temperatures below certain thresholds, concern over climate change, and decreasing costs of data acquisition are only accelerating the amount of stream temperature data now being collected.

A collaborative project by the USFS, NOAA, CSIRO, TU, and USGS funded by the Great Northern Landscape Conservation Cooperative is addressing the issues associated with temperature monitoring and the effects of climate change on several fronts. First, the project is developing a comprehensive, interagency stream temperature database across a five state area in the Northwest. The project area originally encompassed the U.S. portion of the GNLCC but was extended to include portions of the Great Basin LCC and the North Pacific LCC through additional support from USFWS and USGS.

 Map of NorWeST project area

Map showing NorWeST project area

Within this area, hundreds of aquatic professionals from more than 60 federal, state, tribal, and private resource organizations have contributed data to the new NorWeST (Northwest Stream Temp) temperature database, which contains > 45 million hourly temperature recordings and > 45,000 summers of monitoring effort at > 15,000 unique stream sites. The NorWeST database may be the largest in the world and would require an investment of approximately $10,000,000 to replicate.


 Map showing locations of stream temperature data in the NorWeST database

Map showing locations of stream temperature data in the NorWeST database contributed by hundreds of biologists from more than 60 resource agencies. Data represent >45,000,000 hourly temperature records and >45,000 summers of temperature monitoring effort at >15,000 unique stream sites.

Stream Climate Information from Data

The second goal of the project is to use NorWeST data to develop accurate stream temperature models, which will then be used to develop a consistent set of historic and future temperature scenarios for all 350,000 stream kilometers across the project area. Using a new type of spatial statistical model for stream networks, the first temperature models and climate scenarios have been developed for streams in the Salmon and Clearwater river basins that encompass approximately 40,000 stream kilometers in central Idaho.

Map of August stream temperatures for the 1993-2011 period

Map of August stream temperatures for the 1993-2011 period predicted at 1 kilometer resolution from the NorWeST temperature model in the Salmon River basin of central Idaho.

The variables predicting stream temperatures in the models are derived from nationally available geospatial data layers to provide flexibility that would enable future expansion of the model to other parts of the U.S. The air temperature data used to represent climate scenarios with the stream temperature models are derived from the RegCM3 regional climate model predictions developed by USGS (archived at USGS Regional Climate Downscaling). Additional details regarding the stream temperature models are documented at the NorWeST website. Stream temperature data organization and model development are currently ongoing for the remainder of Idaho, Montana, and Wyoming, with anticipated completion dates in spring of 2013. Stream temperature data for Oregon and Washington will be subsequently addressed through the remainder of 2013.

Disseminating Information

NorWeST websiteThe third project goal, aligned with the core principles of the LCCs, is to openly distribute NorWeST stream temperature information so that it can be used in more efficient decision making, and monitoring and planning efforts. A NorWeST website has been launched that hosts a variety of geospatial stream temperature data products, all of which can be displayed in ArcMap and used for spatial database queries. These products include:

  1. summaries of stream temperature data and georeferenced locations of monitoring sites, 
  2. GIS shapefiles of temperature model predictions for climate scenarios, and 
  3. GIS shapefiles of temperature model prediction precision, which are useful for designing efficient monitoring strategies.

As temperature data products are developed and finalized within a river basin, they will be posted to the website and notification sent to the data contributors. Initial responses to these data products have been very positive and download activity from the NorWeST website shows significant use by resource professionals within the Salmon and Clearwater river basins where results are currently available.

The Value of Better Information

Although the raw data assembled in NorWeST have significant monetary value, a much greater value will accrue over time from the improved efficiencies and decision making that accurate geospatial temperature data provide. A series of complimentary projects that use NorWeST model outputs are being developed in parallel, including:

  1. regional temperature and biological monitoring protocols, 
  2. vulnerability assessments for sensitive species,
  3. decision support tools, 
  4. consistent thermal niche descriptions for aquatic species, and 
  5. improved bioclimatic models and projections.

As the NorWeST project progresses, it is developing considerable interest and support across the region, stimulating collaborations and coordination among dozens of resource agencies, and serving as a model for initiatives in other parts of the country through the Landscape Conservation Cooperative system.

Stream temperature graphPhoto courtesy of Dona Horan

This article was contributed by Dan Isaak, Boise Aquatics Sciences Lab, Rocky Mountain Research Station. For more information about this project and Dan's work, vist the NorWeST website and subscribe to Climate Aquatics blog