Citation:

Johnson, Z., S. Leibowitz, AND R. Hill. Developing stressor-watershed function relationships to refine the national maps of watershed integrity. Ecological Society of America Annual Meeting, Portland, OR, August 06 - 11, 2017.

Impact/Purpose:

As part of the Clean Water Act, the EPA is required to report on the integrity of the Nation’s water resources. Human-induced ecological change within stream ecosystems resulting from land-use and cover change, increased water demands and regulation, nonnative species introduction, and climate change is of major scientific concern due to the many social and ecological services provided by these systems. Under the Safe and Sustainable Water Resources research program, previous work concerning estimating and predicting water resource condition has developed an operational definition of watershed integrity, a spatial dataset of landscape indicators (StreamCat) to aid in the evaluation of the conditions of the nation’s streams and rivers, and an index of watershed (IWI) and catchment integrity (ICI) that were mapped for the conterminous United States using this spatial dataset. Currently, there is a need to evaluate and improve the national IWI and related maps which used first-order approximations of relationships between stressors and six watershed functions (hydrologic regulation, regulation of water chemistry, sediment regulation, hydrologic connectivity, temperature regulation, and habitat provision). In this study, we develop metrics associated with the functional watershed integrity components and evaluate correlations graphically and through simple statistics using regional datasets from the Calapooia River (Oregon), Little Miami River (Ohio), and Narragansett Bay (Rhode Island) watersheds. We then used boosted regression trees to model potential stressors used in the initial maps against our developed metrics. Use of locally available GIS datasets with higher spatial resolution and accuracy allows the assessment of possible limitations in use of nationally available GIS coverages. In summary, we found that many of the relationships between stressors and the six watershed functions are non-linear. These relationships display threshold behaviors, where a relatively small range in stressor values produce relatively large changes in a watershed function. This suggests that the IWI and ICI can be improved by substituting these empirical functions for the initial first-order approximations. The information derived from these results and future research is expected to support decisions related to the preservation of watershed integrity and restoration potential at state, regional, and national scales. This study supports an FY19 milestone under SSWR 3.01B.3, “Mapping of watershed integrity, stream condition, and lake condition for the continental US”.

Description:

Abstract ESA 2017Developing stressor-watershed function relationships to refine the national maps of watershed integrityJohnson, Z.C., S.G. Leibowitz, and R.A. Hill. To be submitted to the Ecological Society of America Annual Meeting, Portland, OR. August 2017.Human-induced ecological change within stream ecosystems resulting from various alterations is of major scientific concern due to the many social and ecological services provided by these systems. Previous work by the EPA developed a definition of watershed integrity as the capacity of a watershed to support and maintain the full range ecological processes and functions essential to sustainability. To aid in the evaluation of the conditions of the nation’s streams and rivers, an index of watershed (IWI) and catchment integrity (ICI) were mapped for the conterminous USA using an EPA spatial dataset of landscape indicators (StreamCat). First-order approximations of relationships between stressors and six watershed functions (hydrologic regulation, regulation of water chemistry, sediment regulation, hydrologic connectivity, temperature regulation, and habitat provision) were used in the initial national maps. The work presented here builds on these previous efforts by evaluating and improving methods used in establishing the national maps of watershed integrity.In this study, we developed metrics associated with the functional watershed integrity components and evaluated correlations graphically and through simple statistics using regional datasets from the Calapooia River (Oregon), Little Miami River (Ohio), and Narragansett Bay (Rhode Island) watersheds. We then used boosted regression trees to model potential stressors used in the initial maps against our developed metrics. Although preliminary, we found that many of the relationships between stressors and the six watershed functions are non-linear. These relationships display threshold behaviors, where a relatively small range in stressor values produces relatively large changes in a watershed function. This suggests that the IWI and ICI can be improved by substituting these empirical functions for the initial first-order approximations. We discuss the potential implications of these non-linear relationships for refining the national maps of watershed integrity.ContactZachary C. Johnson, NHEERL/WED(541) 754-4355johnson.zachary@epa.gov

Record Details: