Mapping Watershed Integrity for the Conterminous United States

Watersheds provide a variety of ecosystem services valued by society.  Production of these services is partially a function of the degree to which watersheds are altered by human activities. In a recent manuscript, Flotemersch and others (in preparation), defined watershed integrity (WI) as the “capacity of a landscape, contributing surface water to a single location, to support and maintain the full range of inherent ecological processes and functions essential to the long term sustainability of local biodiversity and the watershed resources and services provided to society.” 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 (CONUS) based on these six key functions by incorporating human landscape stressors that have been shown to degrade key functions in watersheds. A WI index and map for the CONUS provides a consistent way to compare WI across the nation. The WI index can also be decomposed into specific factors that influence index scores that can be targeted for adaptive management by informing protection, rehabilitation, and restoration efforts in watersheds.