Mapping Watershed Integrity for the Conterminous United States

Watersheds provide a variety of ecosystem services valued by society.  Production of these services is sensitive to watershed alteration by human activities. Flotemersch et al. (2015) defined watershed integrity (WI) as the “capacity of a watershed to support and maintain the full range of ecological processes and functions essential to the sustainability of biodiversity and of the watershed resources and services provided to society.” They argue that six key functions must be present for a watershed to have integrity: hydrologic regulation, regulation of water chemistry, sediment regulation, hydrologic connectivity, temperature regulation, and habitat provision. We developed and mapped an index of WI for the conterminous USA based on these six key functions by incorporating human landscape stressors from the EPA’s StreamCat dataset, that have been shown to degrade key functions in watersheds. The index is mapped at 1:100,000 scale at the stream catchment resolution, and provides a consistent way to compare WI across the Nation.  Specific factors that highly influence WI scores may signal effective management targets for protection and restoration of watersheds.