Applying the index of watershed integrity to the Matanuska–Susitna basin

ABSTRACT

The Matanuska–Susitna Borough is the fastest growing region in the State of Alaska and is impacted by a number of human activities. We conducted a multiscale assessment of the stressors facing the borough by developing and mapping the Index of Watershed Integrity (IWI) and Index of Catchment Integrity (the latter considers stressors in areas surrounding individual stream segments exclusive of upstream areas). The assessment coincided with the borough’s stormwater management planning. We adapted the list of anthropogenic stressors used in the original conterminous United States IWI application to reflect the borough’s geography, human activity, and data availability. This analysis also represents an early application of the NHDPlus High Resolution geospatial framework and the first use of the framework in an IWI study. We also explored how remediation of one important stressor, culverts, could impact watershed integrity at the catchment and watershed scales. Overall, we found that the integrity scores for the Matanuska–Susitna basin were high compared to the conterminous United States. Low integrity scores did occur in the rapidly developing Wasilla–Palmer core area. We also found that culvert remediation had a larger proportional impact in catchments with fewer stressors.

KEYWORDS:

• Catchment integrity
• cold climate hydrology
• culvert remediation
• sub-Arctic
• watershed integrity

Acknowledgments

We thank Mark Douglas and Gayle Martin (U.S. EPA); Jonathon Gerken, Bob Henszey, and Catherin Yeargan (U.S. Fish and Wildlife Service); Jeremy Grauf and Jason Brewer (U.S. Army Corps of Engineers); Matthew Varner (Bureau of Land Management); Brianne Blackburn (Matanuska–Susitna Borough); James Rypkema, Laura Eldred, Charley Palmer, Lisa Griswold, and Jeanne Swartz (Alaska Department of Environmental Conservation); Marcus Geist (University of Alaska Anchorage, Alaska Center for Conservation Science); and Matt McMillan (Great Land Trust) for attending the kickoff workshop in Anchorage in November 2017. We also greatly appreciate Gillian O’Doherty and Mark Eisenman (Alaska Department of Fish and Game); Jim Depasquale (The Nature Conservancy); Anne Johnson (Alaska Department of Natural Resources); and Marcus Geist (University of Alaska Anchorage, Alaska Center for Conservation Science) for providing us with data. The authors also thank Brent Johnson, Miriam Glendell, and the two reviewers from AAAR for their input on previous versions of the article.

Jessica Winnestaffer, Melissa Shaginoff, and other Tribal citizens encouraged and co-wrote the Land Acknowledgement—a gesture to recognize the traditional lands on which this research took place.

Land acknowledgments

We acknowledge the Dena’ina and Ahtna Dene (Athabascan) tribes, including Nay’dini’aa Na’ Kayax (Chickaloon Native Village), Idlughet Qayeht’ana (Native Village of Eklutna), Knik Tribal Council, Tebughna (Native Village of Tyonek), their Elders both past and present, as well as future generations who continue to be stewards of this land since time immemorial.

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability

Upon publication of this paper, results will be available at the EPA’s Environmental Data Gateway (https://edg.epa.gov/) and at the U.S. Government open data site (https://data.gov).

Supplementary material

Supplemental data for this article can be accessed on the publisher’s website.

Additional information

Funding

The information in this document has been funded entirely by the U.S. Environmental Protection Agency (EPA), in part by an appointment to the Internship/Research Participation Program at the Office of Research and Development, EPA, administered by the Oak Ridge Institute for Science and Education through an interagency agreement between the U.S. Department of Energy and the EPA. The views expressed in this journal article are those of the authors and do not necessarily reflect the views or policies of the EPA. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.