Citation:

Aho, K., S. Leibowitz, M. LaCroix, AND J. Flotemersch. Matanuska-Susitna Index of Watershed Integrity (AK IWI). Meet with EPA Deputy Asst Administrator for the Office of Water, Anchorage, AK, June 18 - 22, 2018.

Impact/Purpose:

The EPA’s Index of Watershed Integrity (IWI) is used to calculate and visualize the status of natural watershed infrastructure that supports ecological processes (e.g., nutrient cycling) and services provided to society (e.g., subsistence resources). The IWI applied to the conterminous US defined watershed functions specific to running water. However, seasonal ice affects 58% of North America’s streams and rivers. This Alaskan iteration of the IWI focuses on the needs of state partners (e.g., Alaska Department of Environmental Conservation). An Alaska IWI that includes stressors to surface (e.g., glaciers), sub-surface (e.g., permafrost), and seasonal (e.g., river ice) cold-climate hydrology features could provide insights on seasonal functions, both for Alaska and regions of the CONUS that experience a degree of river ice during the winter. This is done using the National Hydrography Dataset Plus High Resolution, information from landscape metrics (e.g., National Land Cover Database), and cold-climate data (e.g., rain on snow events) from the University of Alaska Fairbanks. This work will also contribute to SSWR 3.01B (Assess, Map, and Predict the Integrity, Resilience, and Recovery Potential of the Nation’s Water Resources) by providing a case study of how the IWI can be used in actual management applications.

Description:

The US Environmental Protection Agency’s (EPA) Index of Watershed Integrity (IWI) is used to calculate and visualize the status of natural watershed infrastructure that supports ecological processes (e.g., nutrient cycling) and services provided to society (e.g., subsistence resources). Specifically, the IWI is based on six functions that watersheds with high integrity are hypothesized to provide: hydrologic regulation, regulation of water chemistry, sediment regulation, hydrologic connectivity, temperature regulation, and habitat provision. To assess the integrity of these six functional components, the IWI considers the occurrence of stressors, or risk factors (e.g., agricultural land cover, road-stream intersections, impervious surfaces). The IWI has been applied to the conterminous US and to international basins in the western Balkans. To better support regional decision-making bodies (e.g., States), the EPA is producing a IWI for the Matanuska-Susitna Basin (AK IWI). In the application for the conterminous U.S., the six functions components were defined by anthropogenic stressors to running water. However, in Alaska, 1) anthropogenic stressors to cold-climate hydrology (e.g., increased number of rain on snow events) are significant and 2) all streams and rivers are affected by at least one cold-climate feature (e.g., permanent glaciers and permafrost, seasonal ice and snow).

Record Details: