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Performance of National Maps of Watershed Integrity at Watershed Scales
Citation:
Kuhn, A., S. Leibowitz, Z. Johnson, J. Lin, J. Massie, Jeff Hollister, Joe Ebersole, Jim Lake, J. Serbst, J. James, M. Bennett, J. Renee Brooks, C. Nietch, N. Smucker, J. Flotemersch, L. Alexander, AND J. Compton. Performance of National Maps of Watershed Integrity at Watershed Scales. WATER. MDPI, Basel, Switzerland, 10(5):604, (2018).
Impact/Purpose:
National-scale mapping and assessment of watershed integrity is of value to states and regional watershed organizations initiating healthy watershed programs based on US EPA Healthy Watersheds Program. Knowing the conditions in watersheds is crucial for restoring areas with degraded water quality, as well as protecting healthy waters from emerging problems before expensive damages occur. Achieving the Clean Water Act’s main goal depends on having good information about watersheds – their environmental conditions, possible pollution sources, and factors that may influence restoration and protection of water quality. A national map of watershed integrity provides scientifically sound and consistent data sources, and makes this information public and easily accessible to the wide variety of our partners working toward clean and healthy waters. This research evaluates the utility of applying these national maps of watershed integrity to more regional and local scales to not only identify watersheds with high integrity, but also those at risk, and to help prioritize conservation and restoration at regional and local scales. The results from this evaluation provide strong support for the utility of applying indices of watershed and catchment integrity derived from nationally available data to identify areas of high integrity to target protection and alternatively to identify impacted areas for focusing regional and watershed level restoration efforts.
Description:
Watershed integrity, the capacity of a watershed to support and maintain ecological processes essential to the sustainability of services provided to society, can be influenced by a range of landscape and in-stream factors. Ecological response data from four intensively monitored case study watersheds exhibiting a range of environmental conditions and landscape characteristics across the United States were used to evaluate the performance of a national level Index of Watershed Integrity (IWI) at regional and local watershed scales. Using Pearson’s correlation coefficient (r), and Spearman’s rank correlation coefficient (rs), response variables displayed highly significant relationships and were significantly correlated with IWI and ICI (Index of Catchment Integrity) values at all watersheds. Nitrogen concentration and flux-related watershed response metrics exhibited significantly strong negative correlations across case study watersheds, with absolute correlations (|r|) ranging from 0.48 to 0.97 for IWI values, and 0.31 to 0.96 for ICI values. Nitrogen-stable isotope ratios measured in chironomids and periphyton from streams and benthic organic matter from lake sediments also demonstrated strong negative correlations with IWI values, with |r| ranging from 0.47 to 0.92, and 0.35 to 0.89 for correlations with ICI values. This evaluation of the performance of national watershed and catchment integrity metrics and their strong relationship with site level responses provides weight-of-evidence support for their use in state, local and regionally focused applications.
