Protecting our Nation's waters: How ecological functions factor into jurisdictional determinations following Rapanos

In 2006, the Supreme Court ruled in two cases, Rapanos v. U.S. and Carabell v. U.S., regarding jurisdiction of “waters of the U.S.” under the Clean Water Act.  Following the ruling, Guidance stipulates that jurisdiction is determined, in certain circumstances, based on a “significant nexus”, where hydrological, chemical and ecological characteristics of tributaries and wetlands are assessed to determine their contribution to restoring and maintaining the chemical, physical and biological integrity of the Nation’s traditional navigable waters.  Oftentimes, significant nexus decisions rely on physical characteristics, as site-specific ecological functions are more difficult to determine.  Since 2007, EPA Region 8 has been tracking all significant nexus decisions in the Region (Colorado, Utah, Wyoming, Montana, North and South Dakota).  Here, we review these significant nexus decisions and identify how frequently ecological characteristics are cited, how many waters were determined to be jurisdictional based upon ecological characteristics alone vs. in combination with hydrological and/or chemical characteristics, and what functions are used most frequently for ecological assessment (e.g., habitat services, nutrient transport, etc.).  Understanding how ecological characteristics are currently used in determining jurisdiction can help us to seek out and utilize aquatic ecological research to more effectively protect our Nation’s waters.